1. General Properties of Fruits And Vegetables; Chemical Composition And Nutritional Aspects; Structural
Features
Genreal Properties
Chemical Composition
Activities Of Living Systems
Stability Of Nutrients
Structural Features
2.General Procedures for Fruit and Vegetable Preservation
Fresh Storage
Harvest maturity
Harvest method
Handling systems
Pre-cooling
Chemicals
Coatings
Controlled environment transport
Preservation By Reduction of Water
Content : Drying / Dehydration An
Concentration
Preservation By Drying / Dehydration
Heat And Mass Transfer
Drying Techniques
Fruit And Vegetable Natural Drying - Sun
And Solar Drying
Use Of Preservatives
Osmotic Dehydration
Sun Drying
Shade Drying
Identification of Suitable Designs of Solar
Dryers for Different Applications
Construction of Solar Dryers
Construction Methods And Materials
Technical Criteria
Socio-economic Criteria
Summary
Sun / Solar Drying Tray
Dryers
Preservation By Concentration
Aspects of Preservation by Concentration
Reduced Weight and Volume by Concentration,
Changes From Concentration
Chemical Preservation
Lactic Acid
Acetic Acid
Methods of concentration
Other acidulants
Commonly Used Lipophilic Acid
Food Preservatives
Gaseous Chemical Food Preservatives
Chlorine
General Rules For Chemical Preservation
Factors which Determine/Influence
The Action of Chemical Food Preservatives
Factors Related To Micro-organisms
Miscellaneous Factors
Preservation of vegetables by acidification
Natural Acidificaiton
Factors influencing the texture of
fermented vegetables
Preservation With Sugar
Heat Preservation / Heat Processing
Determining Heat Treatment / Thermal
Processing Steps
Sequence of operations employed in
heat preservation of foods(fruit and
vegetables, etc.)
Technological Principles of Pasteurization
Thermopenetration
Food Irradiation
3.Principles of Refrigerated Gas
Storage of Foods
Gas Packed Refrigerated Dough
Refrigerated Dough
Gas Storage of Fruits And Vegetables
Produce Package System
Subatmospheric Storage
Rarified Air Storage
Gas Exchange Equation
Gas Atmosphere Storage of Meats
Bacterial Counts
Ph of Tissue
Meat Color
Gas Storage of Grains, Seeds and Flour
Underwater Storage
Underground Storage
4.Nature of Food Hazards
Causes of Food Spoilage
Deter Natural Destructive Forces
Food Poisoning
Food Intoxications
Mycotoxins
Food Infections
Epidemiology of Food Hazards
Chemicals in Foods
Nature's Seal of Quality
5. Chemical Preservation of Foods
What Are Food Additives?
Importance of Chemical Additives
Legitimate Uses In Food Processing
Undesirable Uses of Additives
Safety of Food Additive
Functional Chemical Additive Applications
Historical Significance
Additives Permitted and Prohibited
In the United States
Chemical Preservatives
Microbial Antagonists
Other Chemical Additives
Artificial Flavoring
Artificial Coloring
Other Agents
Buffers and Neutralizing Agents
Preservatives (sequestrants)
Nutrients
Stabilizers
Chemical Additives And The Future
6. Food Preservation By Canning
Temperature Vs Pressure
Spoilage of Food Caused By Microorganisms
Heat Resistance of Microorganisms
Important in Canning
Factors Influencing the Heat
Resistance of Spores
Categories of Foods for Canning
Important Food Groups
Microorganisms Associated With The
Food Groups
Influence of Food Ingredients on
Heat Resistance of Spores
Heat Resistance of Enzymes in Food
Heat Penetration into Food Containers
and Contents
Conduction Heating Foods
Measuring the Heat Penetration
into Canned Foods
General Method For Calculating
The Process Time for Canned Foods
Inoculated Pack Studies
Adequacy of Heat Processes
Spoilage of Canned Foods
Microbial Spoilage
Storage Of Canned Foods
External Corrosion of Cans
Coding the Pack
Influence of Canning on the Quality
of Food
Color
Flavor and Texture
Protein
Fat and Oil
Carbohydrates
Vitamins
Misconceptions Relating to Canned Foods
7. Food Preservation by Fermentation
Life with Microorganisms
Fermentation of Carbohydrates
Order of Fermentation
Types of Fermentations of Sugar
Fermentation Controls
Wine
Preservation
Sterilization Filtration
Beer
Cold Pasteurization
Vinegar Fermentation
Principles of Vinegar Fermentation
Vinegar Making
Preparation of Yeast Starter
Alcoholic Fermentation
Acetic Fermentation
Cheese
Kinds of Cheese
Cottage Cheese
Swiss Cheese
Blue Cheeses
Camembert
Hazard Analysis in Cheeses
Mycotoxins and Cheese
8. Food Preservation by Drying
Drying-A Natural Process
Dehydration-Artificial Drying
Dehydration Vs. Sun Drying
Why Dried Foods ?
Dehydration Permits Food Preservation
Humidity-Water Vapor Content of Air
Adiabatic Driers
Heat Transfer Through A Solid Surface
Criteria of Success In Dehydrated Foods
Freeze-Dehydration (Freeze Drying)
Triple Point of Water
Temperature Changes in Meat
Freeze-dehydration
Influence of Dehydration on Nutritive
Value of Food
Influence of Drying on Microorganisms
Influence of Drying on Enzyme Activity
Influence of Drying on Pigments In Foods
Dehydration of Fruits
Dehydration of Vegetables
Dehydration of Animal Products
Dehydration of Fish
Dehydration of Milk
Dehydration of Eggs
Packaging of Dehydrated Foods
Influence of Drying on Food Acceptance
Trends in Drying Foods
Vegetables
Fruit
Meat, Fish and Eggs
Milk
Coffee and Tea
Grain Drying
9.Canning Fruits
Apple
Apricot
Banana
Black Berries
Cherries
Fig
Grape
Grape Fruit
Greengage
Guava
Jack-fruit
Litchi
Loquat
Mango
Orange
Papaya
Peach
Pear
Pineapple
Plum
Berry Fruits
10.Syrups And Brines For Canning
Sugar Syrups
Preparation
Testing Syrup Strength
Temperature Corrections
Syrup Calculations
Brines
11. Fruit Beverages
Squashes And Cordials
Orange Squash
Grape Fruit Squash
Lemon Squash
Lime Squash
Lime Juice Cordial
Citrus Fruit Barley Waters
Jack Fruit Nectar
Jaman Squash or Syrup
Mango Squash
Passion Fruit Squash
Peach Squash
Phalsa Squash
Pineapple Squash
Plum Squash
Water Melon Squash
Other Fruit Squashes
Juices
Syrups
Carbonated Beverages
Fruit Juice Concentrates
Tamarind Juice Concentrate
12. Fermented Beverages
Grape Wine
Fermentation
Packing
Champagne
Port
Muscat
Tokay
Sherry
Cider
Perry
Orange Wine
Berry Wines
13. Jams, Jellies And Marmalades
Jams
Fresh Fruits
Frozen Fruits
Fruits Preserved by Heat Treatment
Sulphitation For Storing
Preparing The Fruit For Jam-Making
Adition of Sugar
Addition of Acid, Colour and Flavour
Boiling Under Vacuum
Storage
Controlled Manufacture
Soluble Solids
Refractometer Method
Total Soluble Solids
Invert Sugar
Sulphur Dioxide
Acidity
Regulating Ph of The Material
Insoluble Solids
Estimation of Pectin
Jellies
Fruits For Jelly
Selection of Fruits
Preparation of Fruits
Extraction of Pectin
Straining And Clarification
Fibril Theory
Spencer's Theory
Olsen's Theory
Hinton's Theory
Test
Controlling The Ph of Jellies
Some Typical Jams And Jellies
Marmalades
Jelly Marmalades
Jam Marmalade
14. Tomato Products
Tomato Juice
Tomato Puree
Tomato Paste
Tomato Cocktail
Tomato Ketchup
Chilli Sauce
Tomato Sauce
Tomato Soup
Microbiology
15. Vinegar
Method of Preparation
Yeast For Vinegar
Preparation of Vinegar
Post-Production Processes
Checking Spoilage
16.Chutneys, Sauces And Pickles
Chutneys
Cooking Process
Bottling
Equipment
Recipes
Apple Chutney
Apricot Chutney
Bamboo Chutney
Mango Chutney
Sliced Mango Chutney
Peach Chutney
Plum Chutney
Tomato Chutney
Thick Sauces
Soya Sauce
Worcestershire Sauce
Mushroom Ketchup (Sauce)
Walnut Ketchup (Sauce)
Thick Sauces
Soups And Soup Mixes
Pickles
Pickling Process
Fermentation In Brine
Various Pickles
Oil Pickles
17.Tin, Glass, And Plastic Containers
For Food Canning
Tinplate Cans
Tinning Processes
The Steel Base
The Tin Coating
Tinplate Temper Grades
Surface Finish
Passivation Treatments
Quality Grading
Corrosion Resistance
Enamel Coatings
Can Manufacture
Glass Containers
Types of Glass Containers
Design Considerations
Plastic Containers
18. Vegetables Preparation For Processing
Basic Steps In Preprocessing
Preprocessing Of Tomatoes
Blanching
Irradiation of Vegetables
Removing Potatoes from Storage
to Processing
Peeling
19.Vegetable Juices, Sauces, And Soups
Vegetable Juices
General Preparation Procedure
Rhubarb Juices And Beverages
Juices From Sauerkraut and other
Fermented Vegetables
Low- Acid Vegetable Juices
Tomato Juice Blends
Concentrated Tomato Juice
Composition, Color, and texture
of Tomato Juice Products
Vegetable Sauces
Dried Sauce Mixes
Vegetables In Soups
Canned Soups Containing Vegetable
Pulps, Emulsions, and Powders
Dry Soup Mixtures
20. Vegetable Dehydration
General Considerations
Unit Loading
Heat Damage
Enzyme Inactivation
Sulfuring
Rehydration
Selection of a Drying Method
Costs of Dehydration
Supplying Heat to Driers
Solar Drying
Types of Driers
Tunnel Driers
Continuous Conveyor Driers
Pneumatic Conveying Driers
Belt-trough Driers
Bin Driers
Spray Driers
Drum Driers
Freeze Driers
Freeze-drying Process
Properties Of Freeze-dried Foods
Packaging and Storage of Dehydrated
Vegetables
Quality Control
Asparagus
Beets
Cabbage
Carrots
Celery
Corn
Garlic
Green Beans
Horseradish
Mushrooms
Onions
Parsley
Peas
Peppers
Pumpkin and Squash
Sweet Potatoes
Tomatoes
21. Freezing of Vegetables
Suitability of Vegetables For Freezing
Overview of Freeze Preservation Procedures
Harvesting
Processing Operations Before Freezing
Freezing Methods
Packaging
Stability and Quality of Frozen Vegetables
Handling, Storage, and Distribution of Frozen Foods
Asparagus
Beans, Green
Beans, Lima
Carrots
Cauliflower
Celery
Corn
Mushrooms
Okra
Onions
Peas, Green
Peppers, Bell
Pimientos
Potatoes
Storage Before Processing
Peeling, Trimming, and Cutting
Blanching
Frying
Freezing and Packaging
Other Products
Squash
Tomatoes
Vegetables-in-sauce
Vegetable Mixtures
22.Pickling and Fermenting of Vegetables
Microbiology of Vegetable Fermentations
Types of Fermented Vegetables
Olives
Chemical Composition
Harvesting and Size Grading
Holding in Brine
Pickles From Cucumbers
Pickles From Other Vegetables
Sauerkraut
Basic Processing Method
Effect of Processing Variables
Production and Use of Sauerkraut
Softening of Pickles
Bloating of Pickles
Role of Yeasts
Reduction of Spoilage in Vegetable
Fermentations

^ Top

FOOD PRESERVATION BY FERMENTATION

LIFE WITH MICROORGANISMS

Microorganisms no doubt outnumber other living entities on this planet and can be found existing actively existing actively or passively wherever living organisms occur. While the energy for life on this planet is captured by green plants in the photosynthetic process, microorganisms are generally responsible for the final decomposition of the photosynthetic products. Animals play a minor role in the cycle.

Inasmuch as bacteria, yeast and molds are to be found throughout the environment of man, it is to anticipated that these microorganisms are in direct competition with other living entities for the energy for the life. Whenever the conditions of nutrients and environment are favorable for microbial activity, it will be found.

Man must compete with all other living entities on earth. In order to retain food supplies for himself, he must interfere with natural processes. Through his study, and as a fruit of his curiosity, man has evolved a number of control systems. One is the preservation of food by controlling, yet encouraging, the growth of microorganisms. Under such a condition, man may employ microorganisms to create unfavorable conditions for other microbes, yet retain in the foodstuffs the nutrients desired.

While microorganisms were not identified as the important agents in food spoilage until a century ago, wine making, bread, cheese making and salting of foods have been practised for more than four thousand years. For all those years mankind practiced food preservation using unknown, invisible, active, living organisms.

TABLE - 1

EXPLOSIVE INCREASE IN BACTERIAL POPULATIONS UNDER FAVORABLE CONDITIONS FOR GROTH: MILK AT ROOM TEMPERATURE

Storage(hr.)	Bacterial count(per ml.)
0	137,000
24	24,674,000
48	639,885,000
72	2,407,083,000
96	5,346,667,000

While food preservation systems in general inhibit the growth of microorganisms, all such organisms are not detrimental. In fact some are commonly utilized in food preservation. The production of substantial amounts of acid by certain organisms creates unfavorable conditions for others.

To review terms for a moment, respiration is that process whereby carbohydrates are converted aerobically into carbon dioxide and water with the release of large amounts of energy. Fermentation is a process of anaerobic, or partially anaerobic, oxidation of carbohydrates. Putrefaction is the anaerobic degradation of proteinaceous materials.

Sodium chloride is useful in a fermentation process of foods by limiting the growth of putrefactive organisms and by inhibiting the growth of large numbers of other organisms. Yet some bacteria tolerate and grow in substantial amounts of salt in solution.

FERMENTATION OF CARBOHYDRATES

The word fermentation has undergone evolution itself. The term was employed to describe the bubbling or boiling condition seen in the production of wine, prior to the time that yeasts were discovered. However, after Pasteur's discovery, the word became used with microbial activity, and letter with enzyme activity. Currently the term is used even to describe the evolution of carbon dioxide gas during the action of living cells. Neither gas evolution nor the presence of living cell is essential to fermentative action, however, as seen in lactic acid fermentations where no gas is liberated, and in fermentations accomplished solely wit enzymes.

There is a clear difference between fermentation and putrefaction. Fermentation is a decomposition action on carbohydrate materials; putrefaction relates to the general action of microorganisms on proteinaceous materials. Fermentation processes usually do not evolve putrid odors, and carbon dioxide is usually produced. In putrefaction the evolved materials may contain carbon dioxide, but the characteristic odors are hydrogen sulfide and sulfur containing protein decomposition products. A putrid fermentation is usually a contaminated fermentation. Putrid kraut or pickles result from microbial growths decomposing protein, rather than the normal fermentation of carbohydrates to acid.

Industrially Important Organisms in Food Preservation

There are three important characteristics microorganisms should have if they are to be useful in fermentation and pickling. (1) The microorganisms must be able to grow rapidly in suitable substrate and environment, and be easily cultivated in large quantity. (2) The organism must have the ability to maintain physiological constancy under the above conditions, and yield the essential enzymes easily and abundantly in order that the desired chemical changes can occur. (3) The environmental conditions required for maximum growth and production should be comparatively simple.

The application of microorganisms to food preservation practices must be such a positive protection is available to control contamination.

The microorganisms used in fermentations are notable in that they produce large amounts of enzymes. Bacteria, yeasts and molds, being single cells, contain the function capacities for growth, reproduction, digestion, assimilation and repairs in cell that higher forms of life have distributed to tissues. Therefore, it is to anticipated that single celled complete living entities (such as yeasts) have a higher enzyme productivity and fermentative capacity than found with other living creatures.

Enzymes are the reactive substances, which control chemical reaction in fermentation. The microorganisms of each genus and species are actually a warehouse of enzymes, with its own special capacity to produce and secrete enzymes. Man has yet to learn to synthesize them.

A dry gram of an organism endowed with high activity lactose fermenting enzymes is capable of breaking down 10,000 g of lactose per hour. This great chemical activity is associated with the simple life-process requirements of the organisms, the ease with which they obtain energy for life, their great growth capacity and reproduction rate, and their great capacity for maintenance of the living entity. One generation may occur in a matter of minutes.

But there is a balance in effort. In living, the organisms consume energy. The product of their actions is a substrate of lower energy than that native material upon which they were planted. However, the product of the activity in the instance of wine is one which man generally enjoys more than the native juice from which the wine was produced.

Order of Fermentation

Microorganisms have available carbohydrates, proteins, fats, minerals, and minor nutrients in native food materials. It appears that microorganisms first attack carbohydrates, then proteins, then fats. There is an order of attack even with carbohydrates; first the sugars, then alcohols, then acids. Since the first requirement for microbial activity is energy, it appears that the most available forms, in order of preference, are the CH2, CH, CHOH, and COOH carbon linkages. Some linkages such as CN radicals are useless to microorganisms.

Types of Fermentations of Sugar

Microorganisms are used to ferment sugar by complete oxidation partial oxidation, alcoholic fermentation, lactic acid fermentation butyric fermentation and other minor fermentative actions.

1. Bacteria and molds are able to break down sugar (glucose) to carbon dioxide and water. Few yeasts can accomplish this action.
2. The most common fermentation is one in which a partial oxidation of sugar occurs. In this case, sugar may be converted to an acid. The acid finally may be oxidized to yield carbon dioxide and water, if permitted to occur. For example, some molds are used in the production of citric acid from sugar solutions.
3. Yeasts are the most efficient converters of a dehydes to alcohols. Many spices of bacteria, yeasts and molds are able to yield alcohol. The yeasts, Saccharomyces ellipsoideus, is of great industrial importance in alcohol in fermentations. The industrial yeasts yield alcohol in recoverable quantities. While other organisms are able to produce alcohol, it occurs in such mixtures of aldehydes, acids and esters that recovery is difficult. The reaction from sugar to alcohol is many stepped.
4. Lactic acid fermentations are of great importance in food Preservation. The sugar in foodstuff may be converted to lactic acid and other end products, and in such amounts that the environment is controlling over other organisms. Lactic acid fermentation is efficient, and the fermenting organisms rapid in growth. Natural inoculations are such that in a suitable environment the lactic acid bacteria will dominate, i.e. souring of milk.
5. Butyric fermentations are less useful in food preservation than those noted previously. The organisms are anaerobic, and import undesirable flavors and odors to foods. The anaerobic organisms capable of infecting man causing disease are commonly butyric fermenters. Carbon dioxide, hydrogen, acetic acid and alcohols are some of the other fermentation products.
6. In addition to the above there is fermentation, which involves much gas production. It is useful in food preservation, although gas production has disadvantages. Energy wise it is less efficient to produce gases (carbon dioxide and hydrogen), which have little or no preserving power in concentrations, found in comparison with lactic acid. Also, the important food spoilage organisms are capable of growing in such environments. In gassy fermentations sugar molecules are altered to form acids, alcohols, and carbon dioxide. It is usually necessary to include some other controlling influence, such as adding sodium chloride to a substrate, with this form of fermentation.
7. There are many fermentative actions possible in foods, which are detrimental to the acceptability of treated foods. Generally the organisms capable of attacking higher carbohydrates such as cellulose, hemicelluloses, pectin, and starch will injure the texture, flavor and quality of treated foods.

Fermentation Controls

Foods are contaminated naturally with microorganisms and will spoil if untended. The type of action, which will develop, is dependent upon the conditions, which are imposed. The most favorable to given type of fermentation under one condition will be altered by slight changes in a controlling factor. Untended meat will naturally mold and putrefy. If brine or salt is added, entirely different organisms will take over.

The pH Value of food is a Controlling Factor - Most foods in native, fresh from which man consumes as food are acid. Vegetable range in pH value from 6.5 down to 4.6 Fruits range from 1.5 down to 3.0. Animal flesh when freshly killed is approximately neutral (7.2) but within two days the pH value will be approximately 6.0. Milk has a pH value near 6.4.

Inasmuch as the two important fermentations in such foods are oxidative and alcoholic, the growth of organisms will be controlled by the acidity of the medium. In fruits and fruit juices, yeasts are less molds will quickly establish themselves. In meat, yeasts are less active than bacteria. In milk, an acid fermentation is established in the mater of a few hours.

Source of Energy - Inasmuch as the immediate need of microorganisms is a source of energy, the soluble, readily available carbohydrates influence the microbial population that will dominate.

In milk the sugar is lactose; those organisms, which quickly mount in numbers, are the lactose fermenting organisms. Because suitable energy sources are generally available to microorganisms in man's foods, energy sources are not usually a limiting factor, with certain exceptions (such as milk).

Availability of Oxygen - The degree of anaerobiosis is a principal factor controlling fermentations. With yeasts, when large amounts of oxygen are present, yeast cell production is promoted. If alcohol production is desired, a very limited oxygen supply is required.

Molds are aerobes, and are controlled by the absence of oxygen. Bacterial populations, which will dominate a substrate, may be manipulated by their oxygen requirements and its availability.

The end product of fermentation can be controlled in part by the oxygen tension of the substrate, other factors being optimum.

Temperature Requirements. - Each group of microorganism has an optimum temperature for growth; the temperature of a substrate therefore exerts a positive control on their growth. To obtain the maximum performance during fermentation, the optimum temperature for the organisms must be created. Examples are available in milk fermentation and also in acetic acid production.

Milk held at 00C has little microbial activity, and retarded expansions in bacterial numbers. At 40C there is slight growth of organisms and more rapid development of off-flavors.

At 210C Streptococcus lactic growth is usually dominant. At 370C Lactobacillus bulgaricus population commonly dominate in milk. At 650C most organism will be killed, but Lactobacillus thermophilius can grow. At 710C souring of milk is generally demonstrated to be due to the presence of Bacillus calidolactis. The temperature of milk is a controlling factor in the above organisms, other factor being equal.

The acetic acid bacteria temperature sensitive, having definite and peculiar temperature relations important in vinegar making. At 70C the organism grows slowly; cells are short and usually broad. At 210C the cells appear normal, growing and developing into chains of cells of varying number. Cell walls become swollen. At 370C long thread- like transparent filaments with no visible cross walls and with irregular bulging, sometimes branching, have been observed. This appears to be a temperature induced, physiologically malfunctioning, pathological condition. Lowering the temperature of the substrate to 260C, that used in the United States in vinegar production, results in the production of some cells with normal characteristics and behavior.

The temperature at which a food is held will deter mine within certain limits the nature of the organisms capable of either yielding the desired fermentation or spoilage, whichever the case may be.

The Action of Sodium Cholride in Controlling Fermentations. - Salt is one of the most important food adjuncts in food preservation. In drying it has been shown to have beneficial effects. In fermentations salt can exert a role in sorting the organisms permitted to grow. We will return to the role of salt and its multiple uses in the next chapter.

CANNING FRUITS

General methods of canning various kinds of fruits are discussed in the following pages. Specific requirements regarding the types of cans, syrup strengths, exhaust and process temperatures, the time factor, etc. are given separately in Table 1.

Apple

Apples are not canned to any great extent, since they can be kept in refrigerated or controlled atmosphere storage for practically the whole year from one season to another. Canned apples, which are usually available in the larger sizes of cans, are generally used in pies. The varieties commonly employed for canning are: Yellow Newton, Pippin, Spitzenberg, Wine-sap, Baldwin, Russet, Jonathan, Delicious, and Rome Beauty.

The fruits are first washed in warm dilute hydrochloric acid to remove any lead or arsenic spray residue and then rinsed in cold water. Next they are peeled by hand or by machine and cut into slices, 0.31 to 0.63cm. thick. The slices are placed in 2 to 3 percent common salt solution to prevent their darkening due to enzyme action. They are then balanced at 710C to 820C for 3 to 4 minutes in plain boiling water or in three per cent boiling brine. Blanching is essential to remove oxygen from the tissues and thus prevent pinholding in the cans during storage. The blanched slices are filled into cans, covered with either hot water or thin sugar syrup, exhausted and processed. Pinholding of cans during prolonged storage, especially in warmer climate, is a serious problem in the case of canned apples.

Apricot

Apricots are canned largely in the U.S.A. In India, these grow mostly in Kashmir, Simla Hills and Uttar Pardesh, where considerable scope exists for their canning.

Apricots are of two kinds; white and yellow. In other countries, the Blenheim variety, which is of moderate size, deep yellow in colour, and has good flavour, and can stand processing well, is popular for canning. The Tilton and Hemskirk varieties are also canned. The white sweet varieties like the Charmagz and Shakarkand have been found by the author to be quite good for canning.

Apricots are not peeled for canning. They are merely cut into halves and the stones removed. Sometimes, they are canned whole. According to Cruess, on as average, a ton of apricots yields about 55 cases of 24 A 2/½ size cans. Siddappa has reported an average yields of 58 cases per ton of apricots.

Banana

Banana is one of the most important fruit crops of India. More than 200 commercial varieties are grown an area of about 1,60,000 hectares.

Das, Jain and Girdhari Lal worked out a method for canning the fruit alone in combination with other fruits in the form of salad. According to them, only a few varieties are suitable for canning. Of the 20 south Indian varieties which they tried. Pachabale, Chandrabale, Nendran, Chenganga purikodan, Poovan, and Vannan yielded satisfactory canned products.

Fully ripe fruit is peeled by hand and cut laterally into slices of 1.27cm. to 1.89cm. Thickness. Sugar syrup of 25 to 300C Brix, containing 0.2 per cent citric acid is used as covering liquid. The pH of the banana has been found to vary from 4.5 to 5.3. Butter size cans (1 lb squat) are processed for 15 minutes in (i) 'bilingn water (1000C), if the pH of the fruit is 4.8 or less, and (ii) in a pressure cooker at 5 lb psi (0.35 kg per cm2) steam pressure (sea level), if the pH is higher than 4.8 Cooling after processing should be quick and thorough to prevent pink discolouration of the slices in the can during storage.

Cloudiness of the syrup in the can slight discolouration of the slices are serious problems in the case of canned bananas. The market for the product is also exclusive and limited, because banana in the green state can be had practically the year round, as a result of recent advances in their harvesting storage and distribution. Indian bananas such as the Cavendish variety are being exported recently to other countries. There is, however, still scope for canning good varieties by improved methods.

Black Berries

Black berries are canned to some extent in the U.S.A. and in the U.K. They are not available in any large quantity in India for commercial canning. Evergreen Mammoth and Himalaya are the more important canning varieties. The berries should be handled without any delay after harvesting.

Cherries

Cherries are grown mostly in Kashmir valley. There are three kinds of cherries -sweet, sub-acid, and acid varieties. The sweet varieties are light coloured with pinkish flesh or of deep red or black colour. According to Siddappa and Mustafa, the White Heart Cherry, which is of fairly big size and has a creamy white flesh, and the Red Cherry, which is rather small in size and has a creamy white flesh, are good for canning. The Royal Anne, the Napoleon Bigarreau and the Kentish Bigarreau are good foreign varieties for canning. These are bright red in colour and taste good. Morello, which is a large cherry of bright reddish purple colour, is important among the acid varieties. It is canned in heavy syrup. Maraschino cherries are canned for mixing with other fruits, fruit cocktails, ice creams, etc. For this, slightly under-pipe Royal Anne cherries are generally used.

The cherries are packed in barrels of brine containing calcium hydroxide, sulphur dioxide, and occasionally alum. According to Cruess in California, the brine for this purpose is made up of about 0.75 to 1.0 per cent SO2 and about 0.4 to 0.6 percent of slaked lime in Oregon, approximately 1.5 per cent of SO2 and about 0.9 per cent of lime are used. The brined cherries are stored for 4 to 6 weeks for curing. During this period, the colour of the cherries changes to white or pale-yellow. The cured cherries are washed well in water and dyed with a red dye such as Erythrosin, and the colour fixed with citric acid. These coloured cherries are used for canning or for candying.

Fig

Figs are usually canned as preserve. They should be allowed to ripen on the tree canned to give a good canned product. Kadota, Celeste, Magnolia and Smyrna are the more important canning varieties. After grading, the figs are wilted by placing them in hot water at 820C for 2 to 3 minutes. They are sometimes lye-peeled and washed with water to remove the waxy coating and the adhering lye. They are then blanched in boiling water for 10 to 20 minutes, depending upon their size and degree of ripeness, and canned in syrup of 450 to 550 Brix. Addition of about 0.5 per cent citric acid to the syrup improves the blend and the keeping quality.

Grape

Muscat and Thompson Seedless are good canning varieties. Only large sized berries are used for canning. Syrup of 200 to 400 Brix is used. Loss in canning is nearly 20%. According to Siddappa and Ishaq, the Seedless Kishmish and the Seeded Haitha grapes give canned products. Coloured grapes should be canned in lacquered cans.

Grape Fruit

Grape fruit should preferably be tree-ripened. Marsh Seedless, Duncan and Foster are good canning varieties are the best for canning.

To remove the thick outer peel, the fruit is immersed in hot water at 930C to 960C for 2 to 5 minutes, so that the peel becomes soft and can be easily removed by hand. The peeled fruit is then either lye-peeled or hand -peeled further. After peeling, the whole fruit is immersed for 20 to 30 seconds in a bath of hot dilute lye containing 1.5 to 2.0 per cent caustic soda. It is then thoroughly washed with cold water and the segments are separated. A clean stainless steel knife of special design is employed to lift the segments are separated, the membranes will be in the form of the leaves of a book. In Florida, sections of peeled fruits are carefully removed by means of a special blunt knife or a knife made of bamboo or some other hard wood. The segments are filled carefully into plain cans, and sugar is added in layers., on layers, or in the form of 600 Brix syrup. Syrup gives a better project. If dry sugar is used, about 56 g would suffice for an A 2 size can. Unlike several other fruits, the filled cans of grapefruit are given a long exhaust of 25 to 30 minutes at 820C to 870C, and processed for 30 to 40 minutes at the same temperature to retain the full aroma and texture of the fruit. The cans are cooled immediately after the processing. Canned grape fruit becomes slightly firmer if kept for some time after canning. The cans should, therefore, be retained for some weeks before marketing.

According to Loesecke, 36 kg of grape fruit yields about 33 cans of A 2 size, when lye peeling is adopted, and 24 to 27 cans when peeling is done by hand.

Greengage

Greengages are canned in syrup containing about 0.5 per cent citric acid. The canned product has, however, a tendency to turn brown and become soft and acquire a bitter flavour during storage. True greengage is fairly satisfactory for canning.

Guava

Guavas of good quality are found in abundance in Uttar Pardesh, Madhya Pardesh, and some parts of south India. Canned guava often have a taste and aroma better than those of even the fresh fruit. The pulp although soft in texture, stands processing well, and does not darken during storage. Fully ripe fruit, preferably with white flesh and few seeds, is selected for canning. It is peeled with knife or sometimes with hot lye, and cut into halves. The seeds are scooped out with a spoon shaped knife. The peeled and cored fruit is kept immersed in 1 to 2 percent common salt solution to prevent it from browning. According to Jain, Das and Girdhari Lal, peel and core can be used for making guava jelly or guava cheese.

Jack-fruit

Jack-fruit (Artocarpus integrifolia) is available in plenty in Maharastra, Bihar, Orissa, Karnataka, Kerala and some parts of Tamil Nadu. It is an important staple food for certain sections of the people in these areas. The tree bears annually 60 to 75 fruits, each weighing 10 to 20 kg. In exceptional cases, the fruit weighs even 35 to 40 kg. The unripe green and immature fruit is prized as a vegetable. Experiments have shown that green jackfruit can be canned as a curried vegetable. The crisp bulbs (seeds removed) as a curried vegetable. The crisp bulbs (seeds removed) of the ripe fruit are used for canning in syrup. The yield of bulbs varies from 25 to 40 per cent of the weight of the fruit.

After cutting the fruit into several large pieces, the bulbs are removed with hand. As the fruit contains white, highly sticky latex, a little gingelly or till oil, or hydrogenated fat (commonly known in India as vanaspati) is smeared on the hand and knife to prevent the latex from sticking to them. The latex is soluble in oil. The seeds are removed from the bulbs, which are then canned whole or as halves or quarters. Syrup of 500 Brix with 0.5 to 0.75 percent citric acid should be used as the pH of the fruit is quite high, i.e., about 5.2. The method of canning jackfruit has been standardized at the Central Food Technological Research Institute,

Mysore.

The canned product has an exotic flavour and is quite likeable, although considered strong by some people. There is scope for large scale canning of this fruit for internal consumption as well as for export to other countries. Siddappa and his colleagues have studies extensively the possibility of canning the fruits of India such as mango, banana, etc, in the form of a fruit cocktail. Highly acidic fruits have been successfully utilized by them to minimize the addition of citric acid to the canning syrup to lower the pH to a safer level for normal processing in boiling water.

The outer rind of jackfruit is rich in pectin and can be used for making pectin. A good jelly can be made out of the rind and also the inner perigones. The seeds can be used as a vegetable, or ground into flour, which can be blended with wheat flour for making chapattis. The seeds contain a trypsin inhibitor, which can be removed by boiling the seeds in salt water. This is by the way the normal practice of eating the seeds. Siddappa and Bhatia have studied in detail the above aspects and also the nutritive value of jackfruit, fresh as well as canned, with or without honey, as supplements to the normal rice diet. The fruit is a valuable one in every respect, and the exotic strong flavour can be reduced considerably by processing and the product made acceptable to a section of people. There is growing interest in the fruit in several quarters.

Litchi

Litchies and found in Uttar Pardesh, Bihar and Orissa. For canning, the fruit should be tree-ripened. The outer shell is first cracked, then the pulp inside is separated, and finally the stones are removed. Plain can and 400 Brix syrup with 0.5 per cent acid are used. Prompt and thorough cooling of the cans after processing is necessary to prevent development of pink colour in the product. Canned litchies from China are well known in foreign countries.

Loquat

Loquat can be cut into halves and canned to get and attractive product.

Mango

India is the home of mangoes. A large number of varieties are found in almost all parts of the country. According to statistics collected by the Fruit Development Adviser, Government of India, out of the total fruit acreage of 12,79,000 ha mangoes alone covered 8,91,000 ha i.e., nearly 70 per cent of total area under fruits. Uttar Pardesh, Tamil Nadu, Karnataka, Bihar and West Bengal lead in mango growing.

Among the numerous varieties, 'Safaida' and 'Dusehri' of U.P. 'Alphonso' of Ratnagiri, 'Badami' of Mysore, 'Benishan' of East Coast, and 'Raspuri' 'Neelam' and Mulgoa' of Tamil Nadu and Karnataka are the most important varieties for canning. The 'Bangalora' or 'Totapuri' mango, which is an assured and heavy annual bearer, and also yields an excellent pulp or juice, is sometimes canned to give a fairly good canned product. Juicy and fibrous varieties are not quite suitable for canning. They are mostly used for making juice, squash, nectar, chutney, and pickles.

Firm ripe mangoes that are just developing colour are picked and ripened in straw. As they ripen, canning ripe fruits are selected daily from the lot. They are washed in water and peeled with hand, and the pulp cut into 6 to 8 longitudinal slices. For canning as halves, the cheeks or the two broad sides are taken. The slices are placed in 2 per cent common salt solution to prevent their enzymic browing. Plain cans are used. As some of the table varieties have a pH slightly higher than the critical pH of 4.2, it is necessary to add 0.3 to 0.5 percent citric acid to the syrup for safe processing of the cans in open cookers. Nowadays, the practice is to sterilize the cans first in open cookers then sterilize them in closed retorts at 1 to 2 pound steam pressure (psi) i.e.0.07 to 0.14 kg per sq. cm, as an additional safety measure. About 0.6 kg. Of the fruit would be required to prepare slices to fill a 0.4 kg. Butter size can. The trimmings of the slices and the pulp adhering to the stone can be utilized profitably for the preparation of mango squash and mango jam.

Mango being the most important and unique commercial fruit of India and known as the king of fruits, it is essential to develop large scale canning and preservation of the fruit. Considerable amount of scientific and development work has been done in the Central Food Technology Research Institute. Mysore, on various problems concerning the mango including the storage and long distance transport. Mango products are likely to find in increasing markets in many countries of the world. Canned mango would, in many respects, compare well with the well known canned peach of commerce.

FRUIT BEVERAGES

FRUITS most commonly used for preparing beverages are sweet orange, mandarin (sangtra) loose jacket orange, sour lime (kazi nimboo or limboo), lemon, grape fruit, grape, apple, mango, pomegranate, phalsa, (Grewia asiatica), jamun (Eugenia Jambolana), mulberry, passion fruit, pineapple etc. Tomato juice also has become quite popular. Among the squashes, sweetened orange juice known, as orange squash, lemon squash and pineapple squash are the most popular ones.

SQUASHES AND CORDIALS

Fruit juices are most commonly packed as squashes or cordials in this country in this country, although canned pure fruit juices like orange and Pineapple juices, and quite recently mango juice are gaining importance. Methods of preparing some of the more important squashes and cordials are dealt with briefly in the following sections.

Orange Squash

Extraction of juice. Orange squash is prepared from tight-skinned oranges as well as from loose skinned oranges like Nagpur and Coorge oranges. Tight skinned oranges are cut into halves either with a knife. The halves are pressed by hand against a revolving burr or rose fitted to a rosing machine. These machines are of various sizes and capacities. The reamed juice is collected in a vessel. In contains plenty of coarse tissues, seeds etc. To remove these, it is filtered through a net cloth or passed through a sieving machine known as pulper, in which the juice gets brushed through a stationary perforated cylinder by revolving paddles of stainless steel, wood or fiber brush. The sieved juice is utilized for making squash. Loose jacket oranges are peeled, and the fibrous rag attached to the segments is removed as far as possible as it is responsible for some of the bitterness in the juice. According to Siddappa, dipping of the segments in hot lye solution for 1/ 2 to 1 minute removes most of parchment-like material enclosing the juice sacs in the segments, and the juice obtained from the treated acid-dipped and washed segments is practically free from substances that subsequently cause bitterness in the juice. This juice has been found to be highly satisfactory for canning as pure as well as for making orange squash. The segments are passed through a screw type juice extractor. Alternatively, the segments may be crushed in a tomato crusher and then passed a coarse sieve to remove seeds, pieces of tissues, etc. Recently, the Taglith-type of juice extractor has been found useful for large-scale storage of orange juice during the season and also for the manufacture of orange squash and canned orange juice practically free from bitterness (Siddappa).

Preparation of Squash. Sugar citric acid, flavouring materials, colour and preservative are added to the juice in correct properties. The method of preparation is practically the same as the one standardized by Lal Singh, Girdhari Lal and other workers, who have given simple recipes for small-scale production. In large-scale manufacture, slight variations in the procedure as well as the proportions of the several ingredients are affected to maintain a standard quality in the product.

Sugar, citric acid and water are mixed and heated. Any dirt is skimmed off. The syrup is cooled slightly and filtered through cloth. The clean syrup is blended with the juice. To improve flavour, peal emulsion of 2 to 4 oranges for every 100 oranges taken or an appropriate quantity of an essential oil and orange essence is added to the squash. The colour of the squash is improved, to satisfy consumer demand, by adding an edible colour like Sunset Yellow F.C.F.Tartrazine, Edicol Orange A.G., etc. in suitable proportions. It is, however, desirable not to resort to the use of colours by gradually educating the public to go in for non-coloured squashes in preference to the ones brightly coloured with artificial dyes. Recently, carotenoid colours such b-carotene, which is the precursor of vitamin available in water-soluble forms. It would be useful to employ these instead of artificial coal tar colours, if it is absolutely necessary to add colour to squashes.

The colour added to the squash should be fairly resistant to the action of sulpur dioxide. Das and Siddappa have recently made a thorough study of the stability of added colour in squash under a variety of preparations as well as storage conditions.

After mixing all the ingredients, a calculated amount of a chemical preservative, namely potassium metabisulphite, approximately about 28 g for every 454 g of squash dissolved previously in a small quantity of the juice or water, is added to the squash. While using stored and So2 preserved orange juice for making the squash, allowance should be made for the acid as well as sulphur dioxide added to the juice for preserving it. The amount of sulphur dioxide in the final product should not exceed 350 p.p.m. of SO2 which is the upper limit permitted by law. By careful attention to hygienic conditions, the concentration of SO2 in the squash can be safely reduced to about 250 p.p.m. This will help in minimizing the last of SO2 in the beverage. The bottle are cleaned and washed in a bottle washing machine fitted with revolving brushes or in a washing machine fitted with jets of hot lye, hot water and steam, to clean and dry the bottles. The sterile are rinsed with hot water before filling them with the squash, leaving about 1.2 to 2.5 cm of headspace. The bottles are then closed with crown corks or pilfer-proof closures, which have been dipped in one per cent potassium metabisulphite solution to sterilize them. The bottles are washed, dried, and labeled. On the commercial scale, bottle-filling machines, with two or more filling heads, based on vacuum, siphon or plunger action, are employed. The labeled bottles are cased and stored in a cool and dry place. The product keeps well for 1 to 1 ½ years without much change in colour, taste and flavour.

Grape fruit Squash

The method of preparation of juice for grape fruit squash is the same as that employed in the case of orange squash.

Lime Squash

Kagzi nimboo is widely used for making lime squash. These lime are available in large quantities in Gujarat, Majharashtra, Andhra Pradesh, Karnataka and Tamil Nadu etc. The fruit is cut into halves with a knife and the juice pressed out from the halves by means of small wooden squeezers or by means of stoneroller type press. The juice is sometimes pressed from the cut fruit by means of a wooden basket press. Seeds are removed by sieving through cloth.

Sugar is first made into syrup, which is filtered and added to the juice. The preserved squash is bottled as usual.

Lime Juice Cordial

Limejuice is stored in large carboys or upright wooden barrels lined with microcrystalline wax. Fifty -six g of the juice of potassium metabisulphite is added to every 45Kg of the juice to preserve it during storage. The juice settles gradually, an the sediment forms a compact layer at the bottom, leaving a clear juice the top. The process takes 2 to 3 months. The clear juice is siphoned off. This method is rather slow and the slow an time-consuming. Clarification of the juice can also be achieved quickly by adding gelatin and tannin in proper proportion, based on preliminary laboratory trials. Sugar, water, colour, if necessary, and preservative are added to the clear juice, and the mixture is then filtered by means of a filter press. Filter aids are added in this process to facilitate filtration. The clear cordial is bottled as usual.

Sugar is added in the form of syrup. The quantity of preservative added to the juice for storage is taken into account while adding the required quantity of it to the cordial. Only a small quantity of colour should be added.

Citrus fruit barley waters

The juice from citrus fruit like lemons, etc is extracted and filtered. A small quantity of barley flour (according to the receipte) is made into a thin paste with a little water. More water is then added to thin the paste. It is then heated to gelatinize the starch of the floor, cooled, filtered and made up to volume.

In the production of squashes in a factory, it is more convenient to work back the recipes to 100Kg of sugar, because one bag of sugar contains 100Kg of sugar. Juice and water can be easily measured by volume making allowance for their specific gravity. For instance, in the case of orange squash, taking one bag of sugar per batch, and keeping 25percent juice in the squash of 45° Brix, the recipe would approximately be as follows:

Orange Squash (234 Kg batch)

Jack Fruit Nectar

Fruit squashes with plenty of fruit pulp in them are known as nectars. They generally contain a higher percentage of fruit in them. They are thick in consistency. Typical examples of fruit nectars are peach, apricot and mango nectars. A similar product has been prepared from jackfruit also.

The bulbs are removed from the ripe jackfruit and after removing the seeds and the thin tissue enclosing the seed, they are passed through a mincing machine. The minced pulp is mixed with about 10percent of its weight of water and passed through a pulper fitted with a fine sieve of 1mm hole. The finely divided pulp obtained is used for preparing jackfruit nectar. Not more than 20percent of the pulp should be added to the nectar, because with percentages of it, the nectar becomes highly viscous and jelly-like.

Jaman Squash Or Syrup

Jaman fruit is crushed and heated in its own juice gently for 5 to 10 minutes at about 60°C to extract the rich purple colour. The heated material is pressed in cloth in a basket press and the clear purple cloured juice used for making the squash, which is highly attractive in appearance and possesses a pleasant taste and flavour with a slight astringency.

JAMES, JELLIES AND MARMALADES

Among preserved fruits, Jams, Jellies and marmalades form an important class of products. During World War II, fairly large quantities of these were important in to India from the U. S.A., and Australia. Now a day, such products are being manufactured extensively in several factories in this country, as by-products or joint products in fruit canning units. They are also made in many of the homes all over the country. Their production and demand can be increased manifold by making better use of cull fruit that is being wasted at present.

Jam is prepared by boiling the fruit pulp with a sufficient quantity of sugar to a reasonably thick consistency, firm enough to hold fruit tissues in position. In its preparation, about 20.4kg of fruit should be used for every 24.9kg of sugar. It should contain not less than 68.5 percent soluble solids as determined by efractometer, when cold, and uncorrected for insoluble solids.

Jelly is prepared by boiling the fruit, with or without addition of water, straining the extract, and mixing the clear extract with sugar, and boiling the mixture to a stage at which it will set to a clear gel. A perfect jelly should be transparent, well set, but not too stiff, and should have the original flavor of the fruit. It should be attractive colour and should keep its shape when removed from the mould. When cut, it should be tender enough to quiver but not flow.

Marmalade is a fruit jelly in which the slices of the fruit or of the peel are suspended. The term marmalade is generally associated with the product made from citrus fruits like orange and lemons, in which shredded peel is in included as the suspended material.

The term fruit jelly covers, in a general sense, jams and marmalades also, which possess the consistency of jelly (whether made from clear juice or from pulp).

JAMS

The method of preparing jams is similar to that used for jelly making, except that pulp and pieces of fruit, instead of clear extract, are used. Jams may be made from a single fruit, or from a combination of two or more fruits.

A jam differs from a preserve in that it does not contain pieces of the whole fruit as in the case with a preserve. In preparing the jam, the fruit is crushed, or otherwise finely cut, so that when cooked, the mass is fairly uniform throughout. A jam is more or less a concentrated fruit possessing a fairly thick consistency and body. It is also rich in flavour, because ripe fruit, which have developed full flavour, are used in its preparation. Pectin present in the fruit gives it a good set. High concentration of sugar facilitates preservation. A great advantage in its preparation is that it can be made completely in a single operation, unlike the preserve, which has to pass through several stages over a number of days, before it is complete. Analytical data for some of the jams from other countries as well as of those made in India are given in the following

A jam manufacturer can choose fruit from among the following five classes:

1. Fresh fruit
2. Frozen, chilled or cold-stored fruit
3. Fruit or fruit pulp preserved by heat
4. Sulphited fruit or fruit pulp, i.e., fruit preserved with sulphur dioxide
5. Dried fruit

Fresh fruits

Fresh fruits generally give the best jams. There are, however, certain difficulties in using fresh fruits. Firstly, the supply of the fruit has to be regular so that it can be used in fresh and sound condition. Otherwise it is likely to spoil, especially in hot weather. Use of fresh fruit for day-to-day manufacture of jams is possible only when the factory has its own orchards in its neighborhood or it is located in an area where the particular fruit required is grown on large-scale. If the fruit has to be transported over long distances, there will be the problem of spoilage during transit. Secondly, due to the short duration of the fruit season, large stocks of the fruit will have to be held in cold storage or frozen or chilled, or preserved with chemicals, or by heat treatment.

As pectin is the main ingredient in the fruit, which gives a set to the jam, it is preferable to use some green fruit, which is rich in pectin along with the ripe fruit to secure the desirable jellying effect in the jam. Over-ripe fruit should not be used as it produces pasty product. In some cases, where the fruit is deficient in pectin, pectin from other fruits or commercial liquid or solid pectin may be added to supplement it.

Frozen Fruits

In a modern fruit preservation factory, a cold store is considered a necessary adjunct. During the season when the fruits are in glut, they are stored to ensure regular supplies to the factory over a period during the off-season. It has been found that the flavour and aroma of the cold-stored fruit remain practically unimpaired, and jams prepared from the cold-stored fruit are as those made from fresh fruit. Fruits, which cannot be kept in cold storage for long periods, are kept in the frozen condition. Some fruits such as cherries and plums discolour badly on freezing and turn brown. Such fruits are frozen after adding sugar or sugar syrup to prevent browning. In this country fresh fruits are generally employed for the manufacture of jams. During World War II, dried fruits, especially apricots, were used to some extent, to meet the demand for special kinds of jams.

Fruits Preserved By Heat Treatment

The fruit is prepared in the same way as for canning, and heated to a sterilizing temperature in hermetically sealed containers. Some-times, a small quantity of sugar is also added to preserve the aroma, colour and texture of the fruit. Plums, Apricots, Pineapples and Peaches are stored without addition of sugar whereas strawberries and raspberries are stored after adding sugar. The added sugar is taken into account at the time of making the jam. This method is not, however, generally used largely for the following reasons:

1. Difficulty of storing the fruit in barrels;
2. Loss of colour in fruits such as strawberries and raspberries during the treatment and subsequent storage;
3. A certain amount of loss of pectin while the fruit remains hot for a long period in bulk packing.

Sulphitation For Storing

For preserving fruits in bulk, sulphur dioxide is universally employed in the form of sodium or potassium metabisulphite, sulphurous acid or calcium sulphite. Calcium sulphite provides an additional advantage in that it hardens the tissues of soft fruit and thereby prevents their disintegration.

The preservative fluid in the fruit should be an aqueous solution containing 0.08 to 0.1 cent of sulphur dioxide. In general practice, the total quantity of sulphur dioxide in the fruit and liquor is kept at 1,500 to 2,000 p.p.m. as a safeguard against any possible leakage of sulphur dioxide.

Sulphur dioxide temporarily bleaches the red colour of fruits like red plums, strawberries and raspberries. The colour is, however, restored when sulphur dioxide is driven off at the cooking stage of making the jam.

According to Baker and Grove, although sulphur dioxide causes complete stoppage of enzymic activities of the fruit, its presence in soft fruit causes the pectic enzymes to convert pectin in to pectic acid, and thereby practically destroys all the jellying power of the pectin of the fruit.

Sulphur dioxide toughens the skin of some fruits as gooseberries and red currants. These fruits should therefore, be heated to boiling temperature and then cooled before adding SO2. This preliminary heating will destroy the enzyme in the fruit that would otherwise, destroy the jellying power of the pectin present in the fruit.

Preparing The Fruit For Jam-Making

The fruit is washed thoroughly to remove any adhering dust and dirt. Leaves, stalks and other undesirable portions are removed. The fruit is then subjected to preliminary treatment, which varies with the type of fruit. For example, strawberries are crushed between rollers. Raspberries are steamed crushed and passed through sieves to remove the hard cores. Plums are heated with a small quantity of water until they become soft, and are then passed through a wide mesh sieve to separate the stones. Sometimes the stones are not removed while making whole fruit plum jam. Cherries are treated in a similar way. Gooseberries are whirled in a rotary vertical cylinder lined with carborundum to rub off the tops and tails. They are then passed through sieves to separate the stalks. Pears are pooled, cored and cut into small pieces. Peaches are lye peeled, and the stones removed. They are then cut into small pieces. Apricots are cut and the stones removed, unless the jam to be made with stones is also included. Mangoes are peeled, stones separated, and then sliced are passed through a pulper. Pineapples are peeled, sliced and the cores punched. The slices are then cut into smaller pieces and passed through a screw-type crusher to get a fairly coarse pulp suitable for making the jam. In the case of loose jacket oranges like Coorg and Nagpur oranges, the segments are separated and lye dipped to remove the outer covering and then passed through a screw type extractor to get a fairly coarse pulpy juice, fit for making orange jam. Bananas are peeled and crushed in a screw extractor fitted with a coarse sieve. Grapes are heated and passed through a screw type juice extractor for getting a coarse juicy pulp. Other fruits are suitably treated to get a fairly coarse pulp suitable for making the jam. The pulp should contain recognisable pieces of fruit. In the case of mixed fruit jam, two or more fruits or pupls are taken in the proportion found suitable for the purpose.

Addition Of Sugar

Generally, cane sugar (sucrose) of good quality is used in the preparation of jam. The proportion in which it is added depends not only on the fruit, but also on its acidity and degree of ripeness. Sweet fruits require less sugar than tart fruits do. The quantity added should be adequate to give the maximum strength to the pectin-sugar-acid gel. To ensure a minimum of 68.5 per cent sugar in the jam, generally 24.9 kg of sugar is required for every 20.4 kg of fruit taken. The finished jam should contain 30 to 50 percent invert sugar, or of glucose, to avoid crystallization of cane sugar in the jam during storage. If the percentage of invert sugar (reducing sugar) is less than 30 cane sugar may crystallize out; if it is more than 50 per cent, the jam will develop into a honey-like mass due to the formation of small crystals of glucose. Alternatively, corn syrup or commercial glucose may be used along with cane sugar to avoid crystallization. Sugar in excess of the requisite quantity should not be added because, if the percentage of total soluble solids becomes very high, the jam becomes gummy and sticky. In case excess of sugar has been added the remedy lies in adding pectin or acid or both to counteract the effect of excess sugar. If, on the other hand, the percentage of soluble solids is low and there is premature setting of the jam, indicating thereby that the materials contains excess of pectin it is advisable to add more sugar. Under exceptional circumstances where more sugar is not added, it would be desirable to and a small quantity of sodium bicarbonate to reduce the acidity and thus prevent re-coagulation.

Addition Of Acid, Colour And Flavour

Acid Generally, citric, tartaric or malic acid, which are natural fruit acids, are used to supplement the acidity of the fruit for jam-making. Addition of acids to fruits, deficient in it, is a necessity because appropriate combination of pectin, sugar and acid is essential to give a 'Set' to the jam. Tarr is of the view that the PH of the mixture of fruit juice and pectin should be 3.1 before sugar is added. According to Hinton, however, purified pectin gives the best 'Set' at PH 2.0. as fruits contain natural buffering salts and other associated materials the best results are obtained when the PH of the mixture is about 3.0.

Colour

Only permitted edible food colours should be used, if necessary, and these should be added towards the end of the boiling process.

Flavour Ordinarily, jams do not require the addition of flavours. If desired, they may be added when jam boiling is nearing completion.

Boiling A steam jacketed pan made of Nickel, Monel metal, Aluminium, Stainless steel or copper heavily lined with tin or silver, is generally used for boiling jams. They are of the stationary or of the tilting type. They are highly convenient for rapid boiling of jams. The fruit-sugar-acid-pectin mixture is boiled in these pans, heated by steam at 60 to 80 psig (4.20 to 5.60 Kg /Cm2). Each batch of mix is in small lots of 45.3 to 54.4 Kg. sugar and fruit are first weighed separately. The fruit is placed in the boiling pan and, if necessary, a small quantity of water is added to facilitate pulping. It is then cooked sufficiently to liberate the pectin. Sugar is added next. The fruit-sugar mixture is then boiled rapidly to concentrate the soluble solids to about 68.5 percent and also to effect the necessary degree of inversion of the sugar. To avoid excessive frothing during boiling a small quantity of butter or some other brand of edible oil may be added to the boiling mixture. If the fruit does not contain sufficient pectin commercial pectin may be added to make good the deficiency.

Boiling Under Vacuum

Sometimes, jam is boiled in a vacuum pan under reduced pressure at a lower temperature of 65° to 76° C. The advantage of vacuum boiling or cooking is that it minimizes the undesirable changes in colour and prevents loss of Vitamin C. The disadvantage, however, is that the jam mixture has to be boiled for a longer time to soften the fruit pieces with the result that there is some loss of flavour. This drawback can, however, be overcome by recovering the volatile esters and putting them back into the jam.

Proper control of boiling is necessary to avoid over concentration of soluble solids, over-inversion of sugar, and hydroyses of pectin.

End Point

In order to make a product of uniform quality, a definite quantity of fruit and sugar should always yield a definite quantity of the finished jam. This can be determined by carrying out a jelmeter test. Generally, in the case of fruits fairly rich in pectin, the weight of the finished jam is one and a half times the weight of sugar taken. The data in the following table would serve as a ready reckoner:

Jam containing 68.5 percent of soluble solids boils at 106°C at sea level. Correction will, however, be necessary for higher locations as the boiling point decreases with increase in the altitude. Generally, the end point for boiling the jam should be about-130°C higher than the boiling point of water at any particular place.

When jam is to be packed in cans, it should be filled hot, and the cans closed and pasteurized for about 30 minutes at 82°C. In the case of A2.5 and larger size cans, it is sufficient to fill the cans hot, seal them and invert them to sterilize the ends for about five minutes and then cool them in water or in air.

Storage

Storage of jam in glass jars, which cannot be hermetically sealed, is rather difficult, as the surface of the jam in the jar is susceptible to mould growth. It should also be remembered that unless the jars are stored in a fairly cool place, moisture will evaporate from the jam resulting in surface graining and also shrinkage of the jam. According to Tomkins, if storage conditions are such as to allow the mould to draw moisture easily from the substratum, the atmospheric humidity will have very little effect on their growth; it will however, have a considerable effect when the movement of water from below is slow, and especially when the surface of the jam is covered with a closely adhering waxed tissue paper. This is true in cases where available water is very low due to the presence of a high concentration of sugar. He further states that most fungi are completely destroyer if they are exposed to humidity less than 90 percent. As a safeguard, jams should therefore, be stored preferably at a place having a relative humidity not exceeding about 80 percent. Hirst and also Morris, state that jams are rarely spoiled by yeasts because of their jelly consistency in which they cannot grow or thrive. There are however, certain strains of osmophilic yeast, which can tolerate the high concentration of sugar in the jams. They cause occasionally some spoilage in jams.

To prevent spoilage of jams by moulds, the filled jars should be left unsealed, but only covered with a disc of waxed paper on the surface of the jam, because moulds do not grow under open conditions are rapidly as in a closed space. The jars should be inspected from time to time and if there by any sign of mould growth, the waxed tissue paper should be changed. If desired, the paper may be dipped in alcohol before placing if on the jam. These jars should be finally sealed only at the time of dispatch of sale. When the jam is to be packed in glass jars, which can be hermetically sealed or in cans, it should be filled hot and the container sealed air-tight and pasteurized at 82°C. for 25 to 30 minutes, depending upon their size. This process is rather inconvenient. In the case of 0.4Kg jars which can be sealed air-tight by means of an R.O. seal, it has been found that if after filling the hot jam into jars to the brim, they are closed with the R.O. seal and the sealed jars inverted for some time to sterilize the closures and then kept in the upright position to cool down, the chance of mould growth is practically negligible. In the case of cans it is sufficient if the closed cans are inverted for 5 to 10 minutes to sterilize the lid, before they are cooled. In the case of jars with jam made from fresh, unsulphited fruit pulp, it is advisable to add to the jam about 40 p.p.m. of sulphur dioxide in the form of potassium metabisulphite, which is permitted by law. This acts as a safeguard against any possible moulding of the surface of the jam. In the case of cans, addition of sulphur dioxide to the jam should be avoided as it leads to blackening of the internal surface of the can. In the case of R.O. closures for jars, and additional precaution would be to dip them in 1 to 2 percent potassium metabisulphite solution for 3 to 4 minutes, then drain them for sealing the jars.

TOMATO PRODUCTS

Fresh tomatoes are highly refreshing and appetizing. They are a good source of vitamins, particularly vitamin C. in this country, tomatoes are grown both in summer and winter, but those grown in winter are superior because they contain more solids. Two types of tomatoes more commonly grown in India are the large and the round ones and the small and oval ones. In other countries well-known varieties like marglobe, sanjose etc., are grown fro their better suitability for preserving and processing. Tomato processing industry packing large quantities of canned tomatoes, tomato paste and puree, tomato juice, sauce and ketchup, is a major food processing industry in some parts of the world like the U.S.A., Canada, Mediterranean countries, Australia, etc. in this country, fairly large quantities of tomato sauces and ketchups popular with the public are being manufactured on an increasing scale, mostly in small units. Large tomato processing units employing fully automatic equipment, have not yet come into being, although proposals to set a few such units are being actively considered.

The tomato changes in colour during different stages of its maturity and ripening i.e., from green to pale-white, yellow and finally red. The yellow colour is owing to the presence of carotene. The red colour appears when the lycopene is formed in the fibres.

As tomatoes are available practically throughout the year in this country there is scope for setting up a large-scale processing industry. Equipment for the purpose is standard and can be obtained without much difficulty. Tomato products are judged by their colour, which in turn, depends on the degree of redness of tomatoes. The red pigment, lycopene, being a highly characteristic and rather unique igment in tomatoes can be used as an index of the amount of the real tomato used in a product. In fact some of the analytical methods are based on this concept.

The following rules should be kept in mind to secure a product of high quality:

1. . Use only plant-ripened red tomatoes as far as possible. The yellow and greenish portions not only mask the red colour of the fully ripe tomatoes, but also turn brown owing to oxidation.
2. . Never use iron equipment at any stage of processing. Lycopene, which is a self-oxidizing isomer of carotene, and to which tomatoes owe their red colour, turns brown when it comes into contact with iron. Iron also forms black compounds with the tannin of the tomatoes or of the spices used. Equipment should be glass-lined, or made of monel metal or preferably stainless steel. Copper equipment also adversely affects the colour of tomato products. Further, there is a severe legal limitation on the amount of copper in tomato products.
3. . Avoid prolonged heating, and cool the product quickly after preparation. Tomato juice, cocktail, ketchup, sauce and soup, and chilli sauce are some of the more important products made from tomatoes. The method of preparing these is described briefly in the following sections.

TOMATO JUICE

For this product, only plant-ripened and fully red tomatoes should be used. All green, blemished and over-ripe fruits should be rejected as they adversely affect the quality of product. Juice got from over-ripe tomatoes is usually thin and not quite pleasant in its taste and aroma.

The yield, colour and flavour of the juice depend on the degree of ripeness of the tomatoes, the variety and the place where grown. The following points should be kept in view to ensure good quality of the juice:

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The juice should be of deep red colour. As the red colour is contained in the fibres, and not in the serum of the juice, the fibrous portion as much as possible should be incorporated in the juice in finely divided condition.

The juice should possess the characteristic taste and flavour of tomato.

The acidity of the juice as citric acid should be about 0.4percent.

The vitamins present in fresh tomatoes should go into the juice during its preparation. Their retention in the juice depends on the methods of extraction used. It has been found that while carotene (B Carotene) is fairly resistant to heat and oxidation in various processes of preparation; Vitamin C (Ascorbic Acid) is lost appreciably, particularly during the screening of the juice, in account of oxidation.

For uniformity in quality, either the tomatoes used should be from one stock and place or the juice should be suitably.

WAHSING AND TRIMMING

Mere rinsing of tomatoes in water is not enough, because mould filaments and other micro-organisms found in the cracks, wrinkles, folds and stem cavities, are not easily dislodged by gentle washing alone. For thorough cleaning, tomatoes should be washed in plenty of running water. For commercial production, rotary washers, or trough washers fitted with moving conveyor belt and soft roller brushes, are generally employed.

Great care should be taken in trimming the washed tomatoes. The loss on account of trimming green and yellowish portions, stalk end, and cracked portions etc., varies from 4.0 to 17.0percent with an average of about 8.0 percent, according to data collected over a period under Indian processing conditions. The heavy wastage is mostly owing to absence of standard varieties for defects in picking, parking, and transport and marketing. The loss can be cut down to a bare minimum by adopting gradually improved methods of handling. Recently, considerable work has been done on several of these aspects with the result that tomato products manufactured in the country are of high quality and stand comparison with similar products produced elsewhere. The methods currently practiced in the Mediterranean countries, Australia etc., for producing and manufacturing tomato products are well suited for maintaining high standards of quality in the products. Large-scale commercial production is however, necessary for attaining this objective.

CRUSHING

After trimming, tomatoes are cut into 4 to 6 pieces for boiling to soften the tissues. Alternatively, they may be crushed by means of fluted wooden roller-crushers.

PULPING

Tomatoes can be pulped by the 'Hot' process or by the 'Cold' process described below:

COLD PUPLING

The crushed tomatoes are boiled in their own juice in steam-jacketed stainless steel pans or in aluminium pans for 3 to 5 minutes to facilitate pulping. This method has the following advantages:

1. The tendency of the juice to separate into liquid and pulp can be overcome if the pectin naturally present in the seed and in the skin can be incorporated into the juice. During the preliminary boiling, this pectin is released and it thickness the pulp. The pectase enzymes, which would otherwise hydrolyse the natural pectin present in tomatoes and thereby make the juice thin, are also destroyed during boiling.
2. Boiling sterilizes the juice party, thereby checking to some extent the growth of micro-organisms, which cause fermentation etc., in the juice. It also inactivates the oxidative enzymes which are responsible for the destruction of Vitamin C in the juice.
3. Alight cooking releases the red colour present in the skin.
4. The yield of juice is higher than in cold pulping of the tomatoes.

COLD PULPING

The tomatoes are crushed in the cold and as such passed through a pulper. This method had the following defect:

1. As compared to the hot process, the extraction of juice is somewhat difficult and the yield is less.
2. Air gets incorporated into the juice in the process of extraction and this oxidizes Vitamin C in the juice. There are, however, suitable equipments available now a day, which minimize considerably the mixing up of air with the juice.
3. The juice extracted by this method is somewhat lighter in colour, since it is necessary to heat the skin to release the colour from the fibrous tissues.
4. the whole process of crushing, pressing etc, has to be completed quickly to avoid microbial spoilage, especially during the initial stages of preparation.

Recently, Penfold has pointed out that cold pulping yields a juice whose flavour and consistency are different from those of the hot-break juice. The manufactures have, therefore, to decide about the type of juice most likely to satisfy the market demand. The flavour of the cold break most is much sharper and more acidic than that of the hot-pulped juice. This is due to the extra pressures applied in the cold pulping and extraction process, whereby the juice surrounding the seeds, which is richer in acid and poorer in sugars than the other portions of the tomato, is extracted first. On account of this, the cold-break juice is also of lighter consistency than that got from hot-break method. It has, however, a better fresh flavour.

EXTRACTION OF JUICE

There are two types of juice extractors in use, namely the continuous spiral press and the cyclone.

Continuous spiral press. This consists of a long spiral screw, which presses the tomatoes against a tapered screen of fine mesh having 25 holes per liner inch, each hole being of a diameter of 20/1,000 of 2.5Cm. the juice passes through the screen, but the skin and seeds are expelled at the lower end of the sieve. When this type of extractor is operated at a speed of about 250 revolutions per minute (RPM), there is practically very little or no incorporation of air into the juice. The crushed tomatoes, which are fed to the screw from a hopper at the upper end, should be subjected to a jet of steam to prevent oxidation and destruction of Vitamins in the juice.

CYCLONE OF PULPER

Juice can also be extracted by passing the crushed tomatoes through a cyclone or pulper. The main defect in this type of machine is that a considerable amount of air is incorporated into the juice. With special attachments to the cyclone, this defect can be minimized nowadays. In these machines, the insoluble solids in the juice are very finely divided and stay in suspension in the juice for longer periods.

In small-scale production, the tomatoes can be strained through Monel metal, nickel or stainless steel sieves having one-millimeter diameter holes. Not more than about 60percent of the fruit should be recovered as juice, because with higher yields, the juice becomes unduly thick and harsh in flavour.

TOTAL SOLIDS

On an average, juice should have a total solids content of 5.66percent (sp.gr.1.0240) at 20°C. the amount of total solids present in the juice can be determined in a number of ways, such as by weighing the dried sample, by nothing the refractive index and by using a specific gravity hydrometer. For routine work, the specific gravity method gives fairly satisfactory results. The juice is strained through a piece of thick cloth, and the specific gravity of the strained juice determined with a hydrometer at 20°C. if the specific gravity is measured at a temperature higher than 20°C, a temperature correction is applied to the reading.

The percentage of total soluble solids is deduced from standard tables showing the relationship between specific gravity and the percentage of solids present in the juice.

COMMON SALT AND SUGAR

On an average, 4 to 6 Kg of common salt is added to every 1000 Kg of the juice to counteract the astringent taste of the juice.

Sometimes, sugar also is added to improve the taste. Addition of about one percent cane sugar to the juice improves the flavour.

PACKING

The juice can be packed in glass bottles or cans. Canned juice has, however, better taste, aroma, colour and keeping quality. Than the bottled juice. Further, the public has got accustomed to the slight metallic tang in the taste of the canned juice, and likes it. This is another typical instance of a product, which becomes popular with public through long usage, in spite of the drawback owing to the presence of traces of metal in it.

The juice is generally homogenized to retard separation of liquid from the pulp and to give it a thick consistency and uniform appearance. It is heated to about 66°C and forced through small orifice under a high pressure of about 70 Kg per square Cm. This shears the particles and tends to reduce all of them practically to the same size. The juice is afterwards heated 82°C to 88°C and filled into hot sterilized bottles of 316 to 454g capacity. The bottles are then hermetically closed by means of crown corks and sterilized for about 30 minutes in boiling water (100°C).

For canning, plain cans are the best, although enameled or lacquered cans also may be used. In this case also, the juice is filled hot into the cans at 82° to 88°C leaving practically very little head-space, to avoid marked loss in colour, flavour and Vitamin C content, which would occur when the headspace is considerable. The cans are then sealed and processed, according to size, as shown in the accompanying table. After processing, the cans are cooled in running cold water

.

In the case of the large No.10 cans, owing to the longer processing time, the juice has generally a slightly cooked taste and flavour.

According to Tressler, Joslyn and Marsh, tomato juice may be presterilized by heating in a continuous heat exchanger to temperatures much above the boiling point of water. The following temperature-time relationship are considered to be approximately equivalent in sterilizing values:

This procedure is effective for destroying the flat-sour organism, B thermacidurans, which often causes trouble in the case of canned tomato juice. Before filling into cans, the juice should be cooled slightly below the boiling point, but should still be sufficiently hot to sterilize the containers also.

ANALYSIS OF JUICE

Lal Singh and Girdhari Lal have made a comparative analysis of four foreign and two Indian brands of tomato juice.

TOMATO PUREE

Commercial tomato pulp without skin or seeds, with or without added salt, and containing not less than 8.37 percent of salt-free tomato solids, is 'Medium Tomato Puree'. It is further concentrated to 'Heavy Tomato Puree' which contains not less than 12 percent solids.

Preparation

The first step in the preparation of tomato puree is the preparation of tomato pulp. This pulp is prepared from plant-ripened tomatoes in the same manner as tomato juice.

PULP CONCENTRATION

Concentration of the pulp is carried out in two types of vessels, namely,

1. Open cooker
2. Vacuum pan.

OPEN COOKER

When dealing with small quantities of the pulp, and aluminium patila (Vessel) will do. For large-scale or commercial production, glass-lined tanks or tanks made of stainless steel, monel metal or nickel, and fitted with flash coils, are used. The open pan method, although employed generally, has obvious disadvantages. During boiling, the juice is exposed to the oxygen in the air, which not only destroys Vitamins in it, but also makes the juice brown. Lal Singh and Girdhari Lal have pointed out that unless special equipment is used to prevent the incorporation of air during the entire manufacturing process, a considerable loss of Vitamin C occurs. Butter or edible oil is added to the juice during boiling to prevent it from foaming, boiling over sticking or burning. Incidentally, it also helps in lessening oxidation. This method has, however, now been superseded by the vacuum pan method, which gives a product of superior quality.

VACUUM PAN

The installation of a vacuum pan is rather expensive for a small factory. Its main advantage is that the juice can be boiled at a much lower temperature under reduced pressure, i.e., at about 71°C, thereby facilitating the retention of the original red colour and flavour of the tomato to a marked degree. As air also is removed during boiling, there is very little likelihood of oxidation or loss of Vitamin C. in order to sterilize the product, the vacuum is broken towards the end and the temperature raised to 100°C and maintained at that level for about 10 minutes.

VACUUM CONSISTENCY

The two methods used for the concentration of pulp are as follows:

Method I Sufficient pulp is transferred to the boiling pan till the heating coils are fully covered. Heating is then commenced. More juice is added and the heating continued till the pan is practically full of pulp. Heating is then stopped and the total solids content of the pulp determined. If the total solids content is higher than the required percentage, more juice is added to lower it; if it is lower, concentration is continued till the desired concentration is reached. Manufacturer generally finds it easy and convenient to follow this method.

Method II In this method, a known volume of the juice is concentrated to a known volume of the finished pulp. The juice is let into the boiling tank and when the heating coils have been fully covered, heating is commenced and the tank is filled to capacity. Heating is continued till the pulp begins to boil vigorously. Steam is then shut off momentarily and the volume of the hot pulp is measured with a measuring stick. Then a small sample of the pulp is drawn for the determination of tomato solids is being carried out, boiling of the pulp in the tank is continued. The pulp is boiled down to the desired specific gravity. As both the original and the final measurements of volume are taken at the boiling points, temperature correction for the reading is not necessary.

The end point

The total solids in the juice, in the beginning, during boiling and the finishing point can be determined either with a specific gravity hydrometer or with and Abbe or pocket refractometer, or by drying the juice in vacuum at 70° C. In practice, the first two methods are employed, as they are fairly simple.

Packing

Tomato puree can be packed in plain as well as lacquered cans. The puree is into the cans, scalding hot, at 82° to 88°C., and the cans closed without exhausting them first. In the case of 453g cans, they are processed, for 20 minutes at 100°C. Larger cans are not generally processed, the temperature of the hot puree itself being sufficient to sterilize the cans also.

VINEGAR

Vinegar is perhaps the oldest known fermentation product. It contains about 5 percent of acetic acid in water, varying amounts of fixed fruit acids, colouring matter, salts and a few other fermentation products, which impart a characteristic flavour and aroma to the product. In the trade, vinegar is labeled according to the material used in its manufacture. For instance, vinegar made from malt is called 'Malt Vinegar' and the one made from apple juice, 'Cider Vinegar' and so on.

QUALITY STANDARDS

Vinegar is a liquid derived from various materials, containing sugar and starch, by alcoholic and subsequent acetic fermentation it should contain at least 4 grams of acetic acid per 100ml and a corresponding quantity of the mineral salts of the material from which it is made. It should not contain arsenic in amounts exceeding 0.0143 milligrams per 100ml nor any mineral acid, lead, copper, or colouring matter except caramel.

GRAIN STRENGTH

Vinegar manufacturers and dealers represent the percentage of acetic acid in terms of 'Grain Strength'. The 'Grain Strength' of a vinegar is ten times the percentage of the acid present in it. For example, a vinegar containing 5 percent of acetic acid is spoken of as vinegar of '50 Grain Strength'.

TYPE

Vinegar is made from various fruits and also from sugar, some important types of vinegar are described in the following section.

CIDER VINEGAR

Vinegar made from apple juice by fermentation is called 'Apple Cider Vinegar' or simple 'Cider Vinegar'. It should contain at least

1. 1.6 grams of apples solids per 100 ml of which more than 50 percent are reducing sugars. 2. At least 4 grams of acetic acid per 100 ml at 20°C.

WINE OR GRAPE VINEGAR

Vinegar made from grapes by acetic fermentation is called 'Wine Vinegar' or 'Grape Vinegar'. It should contain at least one gram of grape solids, 0.13 grams of grape ash and 4 grams of acetic acid per 100 ml at 20°C.

SPIRIT VINEGAR

This type of vinegar is made by acetic fermentation of dilute ethyl alcohol. It should contain at least 4 grams of acetic acid per 100 ml at 20°C. It may be coloured with caramel. This vinegar is called 'Grain Vinegar' or 'Distilled Vinegar'.

Distilled vinegar is often called 'White Vinegar'. The terms 'Distilled' is misleading, because the vinegar is not distilled, but is made from alcohol, which is distilled.

MALT VINEGAR

Malt vinegar is derived wholly from malted barley or other cereals, the starch of which has been saccharified by the diastase of malt and the sugars formed fermented into alcohol and the alcohol subjected to subsequent acetic fermentation with distillation of the alcohol as an intermediate step. This vinegar contains not less than 4 grams of acetic acid per 100 ml at 20°C.

OTHER VINEGAR

Vinegar can be made from orange, pineapple, ripe banana, pear, peach, apricot, etc., and in fact from any substance which contains at least 10 percent of fermentable sugars and which will yield more than the legal limit of 4 grams of acetic acid per 100 ml of the vinegar.

METHOD OF PREPARATION

Two distinct processes are involved in the preparation of vinegar, i.e. (I). Transformation of the sugary substances of fruits etc., in to alcohol by yeast, (II) Changing of the alcohol into vinegar by acetic acid bacteria. The chemical reactions involved in these two processes can be represented as follows:

RAW MATERIAL PROCESSING AND FERMENTATION

GRAPES

Grape are crushed and pressed just as in the case of making white grape juice and are then fermented with a pure culture of starter yeast. The fermented juice usually contains a much higher percentage of alcohol than that required for vinegar preparation. The liquor is adjusted to 7 to 8 percent alcohol content before starting acetic fermentation. The fermented juice should be diluted only at the time of starting the acetic fermentation, because otherwise, it may spoil owing to the formation of 'Wine Flowers'.

ORANGE

While extracting orange juice for fermentation, care should be taken to keep out the peel as it interferes with alcoholic fermentation by yeast.

APPLE

Apples are grated and pressed in a basket or rack and cloth pressed to get the juice. Even after this, the pomace contains a large percentage of juice, which is rather difficult to extract. To extract this residual juice the pomace is ground finely. For every 1016 kg of the ground material about 68.1 litres of actively fermenting cider is added in order to promote yeast fermentation. The pomace is allowed to ferment for 2 or 3 days and then pressed. By this method, a larger yield of juice is obtained than by simple grinding and pressing. The juice extracted by this method, being of slightly inferior quality, should be fermented separately.

DRIED FRUITS

Dried fruits normally contain a much higher percentage of sugar than fresh fruit, the percentage varying from 50 to 70. For preparing the solution for making the vinegar, 227 to 272 litres of water is added to every 45.3 kg the dried fruit, so as to get a juice containing 10 to 15 percent of fermentable sugars. Then a starter of pure wine yeast is added, and the mixture allowed to ferment for 2 to 3 weeks, or till the fruit become sufficiently soft. During this process, the mixture is stirred twice a day to prevent the growth of mould and acetic acid bacteria on the surface. The fermenting material is then pressed in a rack and cloth pressed, and the juice allowed to ferment further till all the sugar present in it, is converted in to alcohol. The alcohol is subsequently fermented to vinegar by acetic acid bacteria.

POTATO

The starch is first extracted and hydrolysed with diastase before further fermentation takes place.

MOLASSES

The materials is diluted to about 160 Brix, neutralized with citric acid and then fermented into alcohol for subsequent acetic fermentation.

HONEY

Low grade honey is generally utilized for the preparation of vinegar.

MALT VINEGAR

For the preparation of high grade malt vinegar, barley is commonly used. According to the methods given by Mackenzie, Hopkins and Kraus, barley is malted as follows:

1. Soaking in water: The barley grain is soaked in water for about 48 hours during which period, it absorbs 45 to 47 percent of water. 2. Germination: the germination of the grains is generally carried out by two methods. In the order methods, the steeped grain as spread on the floor of a well-ventilated room till the plumules are about three fourth of the length of the grains. During germination the grain becomes soft and mealy, and diastase is produced. The temperature of the grains rises. To prevent this, the grain is turned over periodically. The temperature of the grain should not be allowed to rise above 25°C. The ideal temperature is 12° to 13° C. It usually takes about a week for the grain to germinate under these conditions. In the more recent method, the germination is carried out in large revolving drums. Even in the floor method, in large scale malting of barley for manufacture of beer, mechanical devices for ranking the grains and thermostatic controls are freely employed to secure efficiency and uniformity. 3. Kilning The sprouted grain is heated in a kiln to stop further growth. The drying should be carried out slowly and gradually so that a temperature of 49°C to 54°C is reached in 40 to 48 hours. On no account should drying temperature exceed this range, because at higher temperatures, the diastatic activity of the malt is adversely affected, and it may be even totally be destroyed. 4.Cleaning and Crushing After drying, the grain is rubbed, sifted to remove the broken plumules and then crushed between rolls into fine particles or grists. 5.Mashing The malt, alone or mixed with fresh ground barley, is suitably thinned with water and heated gradually from 540 to 770°C. The temperature is then raised to about 930 cand kept at that point for about half an hour to gelatinize the starch. The mixture is then cooled to 650°C, and a fresh portion of malt is added to complete the hydrolysis of starch. The progress of conversion of starch is tested with iodine, which gives a blue colour with starch, but does not give any colour with sugar. The liquid is then run off, cooled and adjusted to about 150 Brix for subsequent alcoholic fermentation. If cereals other than barley are to be used, the method followed is flightly different. The starch in the cereal is first gelatinized by pressure-cooking and a certain amount (10 to 15percent) of barley malt is added to convert the starch into maltose. The mash is then fermented with pure yeast such as saccharomyces cerevisiae into alcohol and finally to acetic acid.

YEAST FOR VINEGAR

The most desirable yeast for fermentation of juices and other sugary materials used in the manufacture of vinegar are saccharomyces ellipsoideus, Saccharomyces malei, and Saccharomyces cerevisiae. These yeasts are highly efficient in converting sugar into alcohol. These settle quickly after alcoholic fermentation is complete and produce a clear liquid of good flavour and normal appearance. In practice, only Saccharomyces ellipsoideus commonly found in grape juice fermentations, is employed for fermentation of the juices on account of its rapid growth and high alcohol forming power. For fermentation mashes made from starchy materials, the yeast of the Saccharomyces cerevisiae group are the best.

Alcoholic Fermentation

Fruit juice and sugar solutions of low concentration ferment of their own accord owing to wild yeast normally present in fruits and in the atmosphere, but this not desirable, because different yeasts produce different kinds of decomposition products. In order to get a vinegar of good quality, it is, therefore, essential to destroy all these naturally occurring yeasts and other micro-organisms by pasteurizations, and then to inoculate the sterile juice thus obtained with pure yeast. Pure wine yeast is available from research laboratories and fermentation factories in a compressed form. A 'Starter' is prepared from this and added to the fruit juice or sugary solution to be fermented.

Yeast Starter

A 'Starter' can be prepared as follows; Take 4.5 litres of fruit juice or sugar solution (Generally jaggery gur) or molasses is used for purpose of about 160 Brix, heat it to about 82°C for about a minute and then cool it to 27°C to 29°C. To this juice, add one cake of yeast after crushing it. Mix the crushed cake thoroughly and place the juice in a clean jug or a stone or glass jar. Close the mouth of the jar with a plug made of cotton or a piece of muslin cloth. Keep it in a dark and warm place at about 27°C.

Yeast requires certain nutrients, such as phosphates, ammonium and potassium salts and sugar. These are normally present in fruit juices and sugar solutions made from gur and molasses. When fermentation becomes active in 3 to 4 days and the juice still shows a Brix of about 8 degree, it is mixed with fresh juice or sugar solution in the ratio of one to ten. The mixture is kept in a warm place for further fermentation. The fermenters are usually open wooden vats. Sometimes, closed fermenters are used so that the carbon dioxide evolved may be recovered. Addition of 85 to 113g of sulphur dioxide (170 to 226g of potassium metabisulphite) 1016 Kg of the crushed fruit or 908 litres of juice, helps in getting higher yields of clear alcohol.

Cultu

re Yeast

The growth of 'Culture Yeast' is favoured by aeration of the fermenting liquid in the initial stages. Undue aeration should, however, be avoided at the later stages to prevent any oxidation. The best course is to fill a barrel to the brim, leaving only a little space of frothing. The mouth of the container should be plugged loosely with cotton, or covered with a piece of muslin cloth to allow the carbon dioxide formed during fermentation to escape.

The most favourable temperature range for the growth of yeast is 25 to 27°C. Fermentation becomes abnormal at 38°C and ceases altogether a 41°C. It also ceases if the temperature of the fermenting liquid falls below 7°C. In order to get satisfactory results, the best course is to use a room whose temperature remains within the range mentioned above.

Alcoholic fermentation occurs in two stages. The first is the preliminary or vigorous fermentation stage and the second is the slow fermentation stage. During the first 3 to 6 days, most of the sugar is converted alcohol and carbon dioxide. This fermentation is so rapid that foreign micro organisms have very little chance to develop in the medium.

The secondary fermentation is much slower and usually takes 2 or 3 weeks. During this fermentation, contamination with vinegar or lactic acid bacteria may take place. 'Stuck Tanks' in which alcoholic fermentation has ceased before it is complete are not uncommon during this stage. This may be owing to either unfavourable temperature or the high sugar content in the solution to yield 14 percent or more of alcohol, which is deleterious for the growth of yeast. Under favourable conditions fermentation is complete in 72 to 96 hours.

Completely fermented juice usually gives a reading of about zero degree Brix or less. On no account, more than 0.3 percent sugar should remain unconverted. During fermentation is, gas bubbles are constantly produced. When fermentation is complete, their evolution ceases.

Clarification and Storage

When fermentation is complete, the yeast and the fruit pulp settled form a compact mass at the bottom of the tank. After settling, the fermented liquid is separated from the sediment by siphoning. A filter press may be used to clarify the liquid. The clear liquid is stored in air tight vessels for use later on. In order to prevent any loss of alcohol to the quality of the product owing to the growth of mycoderma 'Wine Flowers', the barrel should be filled to the brim and sealed. If, however, fermented liquid is to be kept exposed, it should either be acidified with strong unpasteurized vinegar so as to increase its acidity to at least one percent acetic acid, or it should be covered with neutral oil, such as liquid para to prevent the growth of 'Wine Flowers' and also to prevent evaporation of vinegar

.

Acetic Acid Fermentation

Acetic acid fermentation is brought about by acetic and bacteria (Acetobacter). These are strongly aerobic and like other organisms, their activity is greatly reduced or inhibited by direct sun's rays. Even diffused day light checks their growth. Acetic fermentation should, therefore, be carried out in dark rooms fitted with orange or red glass panes.

Acetic acid bacteria require for their growth, nutrients which are generally present in the alcoholic liquor made from fruit juices or sugary substances. If, however, distilled alcohol is used addition of food for the bacteria becomes essential. Usually malt sprouts, phosphoric acid, potassium carbonate, trisodium phosphate and ammonium hydroxide are used. For acetic fermentation, the alcohol content of the fermented liquid is adjusted to 7 to 8 percent alcohol because acetic acid bacteria do not function properly at higher strengths. Mother vinegar containing acetic acid bacteria is then added to it in order to check the growth of undesirable micro-organisms and to hasten the process. It is generally added at the rate of one part to three parts of the fermented juice.

PREPARATION OF VINEGAR

Slow Process

The slow process, covering a prolonged period, is generally adopted in this country. The juice or sugary solution is filled into barrels and allowed to undergo alcoholic and acetic fermentations slowly. To screen off dust and the barrel is placed in a damp, but warm place. In about 5 to 6 months, the sugar solution turns into vinegar. The main drawbacks of this otherwise simple method are:

1. Alcoholic fermentation is often incomplete;
2. Acetic fermentation is very slow;
3. Quality of the vinegar is inferior;
4. Yield is low.

Orleans Slow Process

In this process about three fourth of the barrel is filled with the juice, inoculated with mother vinegar, and the barrel placed on its side. Two holes, each about 2.5 Cm in diameter, are made on either side of the barrel just above the level of the juice in addition to the bung hole. These three holes are screened with wire-gauzxe or cheese cloth to exclude insects, vinegar flies etc. the barrels are kept in a warm place at 21° to 27°C, and fermentation is allowed to proceed till the acid reaches its maximum strength. Under favourable conditions, it usually takes about 3 months for the complete conversion of the liquid into vinegar. About three fourth of the vinegar is then withdrawn and an equal quantity of fermented alcoholic juice is added for further vinegar fermentation. The process can be repeated once in very 3 to 4 months. Care should, however, be taken to see that the vinegar bacteria on the surface of the fermenting juice is not disturbed, otherwise the broken film will sink to the bottom, and in the absence of air exhaust the nutrients without producing any vinegar. In order to avoid the breaking and sinking of the film, a perforated support may be placed in the barrel, about 2.5 Cm below the surface of the fermenting liquid, to support the film, when the vinegar is withdrawn. Vinegar produced by the Orleans slow process ages during the process of fermentation, and is clear and of superior quality.

Quick Process

This process is called the 'Generator' or the 'German' process. Additional supply of oxygen is made available for the bacteria by increasing the surface for the action of the bacteria culture. This increases the rate of fermentation. The equipment used in this process is known as 'Upright Generator'. It has a false bottom and head, ventholes and sparge for discharging the liquor. It consists essentially of three compartments, namely central, distribution and receiving compartments are as follows:

Central Compartment

This is filled with beech-wood shavings, corncobs, pumice stone, rattan shavings or straw to increase the surface area. This chamber is fitted with an adjustable opening near the bottom for admission of air.

Distributing Compartment

This is about 30 Cm above the central compartment and is separated from it by a partition, which is perforated with a number of small holes. In this compartment, a revolving sprinkler or a tilting through, is fitted to allow the liquid to trickle slowly over the shavings or other material in the central compartment.

Receiving Compartment

This is the bottom chamber of the generator in which vinegar is collected. It is separated from the central compartment by a perforated partition about 1.5 metres from the bottom of the generator.

The beech-wood shavings or the fillings material is wetted with unpasteurized vinegar. A mixture of two parts of the alcoholic juice and one part of vinegar is fed slowly through the generator to stimulate the growth of vinegar bacteria. Within a few days, the growth of the bacteria becomes sufficient to permit the normal operation of the generator. When the generator is ready, the alcoholic liquid is mixed with mother vinegar in the ratio of 1:2 to increase the acidity from 3 to 3.5 percent. It is then passed through the generator will convert the remaining alcohol into acetic acid. The process can be made continuous. The progress of oxidation is determined by finding the increase in acidity of the percolating solution.

The generator and the air passage should be cleaned from time to time to eliminate undesirable micro-organisms. The optimum temperature at which vinegar bacteria are active is 27° to 30°C. In the generator, this is controlled by the adjustment of air intake and by regulating the rate of flow of the liquid. If the temperature falls, the rate of alcohol is decreased and the passage of air increased. For speedy work in all seasons, generators may be fitted with coils through which cold water or steam may be passed to maintain the optimum temperature.

ALCOHOL AND ACETIC ACID YIELDS

Theoretically, 100 parts of sugar (Sucrose or Maltose) should yield 53.8 parts of alcohol or 70.1 parts of acetic acid. In actual practice, however, even under the most favourable conditions, 44 to 47 parts of alcohol and 50-55 parts of acetic acid only are produced. The loss represents the consumption of sugar in solution by the yeast, loss of alcohol and acetic acid owing to evaporation of oxidation and also loss owing to utilization by vinegar bacteria for their growth. Small quantities of alcohol also may remain unconverted. In order to prepare a vinegar of about 5 percent acetic acid strength, it is, therefore, necessary, to use a juice with atleast 10 percent sugar (Maltose or Sucrose) content. After conversion of the whole of the alcohol into acetic acid the vinegar bacteria attack the acid itself. This can be prevented by filling the barrels to the brim and sealing them airtight.

VEGETABLE DEHYDRATION

Dehydration is an ancient method for preserving food. It lowers the costs of packing, storing and transportation by reducing both the weight and volume of the final product. Sun drying of certain fruits such as apricots and peaches is common wherea