Complete guide for preserving fruits and vegetables for a very long time. Also learn about:- 1. Introduction to Fruits and Vegetables Preservation 2. Principles and Methods of Fruits and Vegetables Preservation 3. Preservation for Fruit Beverages 4. Preserving Vegetables.
1. Introduction to Fruits and Vegetables Preservation:
All living creatures, including humans depend on nature for their food. We live from hunting and fishing, agriculture and animal husbandry. Most of our food consists of agricultural and animal husbandry. To make food available throughout the year, humans have developed methods to prolong the storage life of products to preserve them.
Food preservation usually involves preventing the growth of bacteria, fungi (such as yeasts), or any other microorganisms as well as retarding the oxidation of fats that cause rancidity. Fruits and vegetables provide an abundant and expensive source of energy, body-building nutrients, vitamins and minerals. During the harvest season, fresh produce is available in abundance, but at other times it is scarce. Moreover fruits and vegetables are only edible for a very short time unless they are properly presumed.
Fruits and vegetables are an important supplement to the human diet as they provide the essential minerals, vitamins and fibre required for maintaining health. The fruits and vegetables are highly perishable commodities. Both respiratory and transpiratory rates are proportional to temperature increases and so that they produce quickly dries, wilts and spoils unless properly preserved.
Approaches for Preserving Fruits and Vegetables:
Two approaches are possible for solving this problem:
1. Creation/expansion of cold storage facilities in the fruit and vegetable producing regions themselves, as also in the major urban consumption centers, to ensure supply of fresh fruits and vegetables throughout the year.
2. To process the fruits and vegetables into various products which could be preserved for a long time and add to the value of the product.
In India, there are 4000 processing industries are functioning. But a marginal quantity of 1.0 to 2.0% of the produce is processed and packaged in contrast with developed and developing countries, i.e., 70 to 80%. Thus, we can see an enormous scope and potential for the expansion of fruits and vegetable industries in India in the future.
Importance of Fruits and Vegetable Preservation:
i. Prevention of colossal wastage of fresh produce. Preserving Fruits: How to Preserve Fruits and Vegetables?
ii. To extend the shelf life of the produce.
iii. To develop value added products.
iv. Self-employment opportunities.
v. Provides convenient and preferable forms to the consumer.
vi. Foreign exchange earnings from the export of processed foods and it will improve our national economy.
vii. Available in the form of ready to serve and hence (fuel consumption) energy is saved.
Need for Preservation of Fruits and Vegetables:
Freshly harvested or prepared products are highly attractive in appear once and possess good taste and aroma, but deteriorate rapidly if kept sometime.
Fermentation caused by moulds, yeast and bacteria. Enzymes present in the products may affect the colour and flavour adversely. Chemicals present in the food react with one another and spoil its taste and aroma.
Air coming in contact with the product, may react with the glucosidal materials present in it and render the product bitter. Traces of metal from the equipment may get into the product and spoil its taste and aroma.
2. Principles and Methods of Fruits and Vegetables Preservation:
Preservation is the measures employed to prevent or minimise all such undesirable changes takes place due to spoilage, which caused by both internal and external organism.
Methods of fruit and vegetables preservation are given as follows:
When food preserve for short duration is called temporary preservation.
These are as follows:
(i) Asepsis:
It means preventing the entry of microorganisms. The inner tissues of healthy plants usually are tree from microorganisms and if any microorganisms are present, they are unlikely to initiate spoilage. If there is a protective covering about the food, microbial decomposition is delayed or prevented.
Examples of such coverings are the shells of nuts, skins of fruits and vegetables, husks of ear corn, the shell of egg and the skin, membranes or fat on meant or fish.
It is only when the protective covering has been damaged or decomposition has spread from the outer surface that the inner tissue are subjected to decomposition of microorganisms.
Washing or wiping of fruits and vegetables before processing should be strictly followed as dust and soil particles adhering to the materials contain microorganisms and by doing so the number of organisms can be reduced considerably.
Packaging of foods is a widely used application of asepsis. The covering may range from a loose carton or wrapping, which prevents primarily contamination during handling, to the hermetically sealed container of canned foods, which if tight, protects the processed contents from contamination by microorganisms.
(ii) By Low Temperature:
Microbial growth and enzyme reactions are retarded in foods stored at low temperature. The lower the temperature, the greater will be the retardation.
Low temperature can be produced by:
(a) Cellar Storage about 15°C:
The temperature in cellar (underground rooms) where surplus food is stored in many villages is usually not much below that of the outside air and is seldom lower than 15°C.
It is not enough to prevent the action of many spoilage organisms or of plant enzymes. Root crops, potatoes, cabbage, apples, onions and similar foods can be stored limited periods during the winter months.
(b) Refrigerated or Chilling (0 to 5°C):
Chilling temperature are obtained and maintained by means of ice or mechanical for refrigeration.
It may be used as the main preservative method for foods or for temporary preservation until some other preservative process is applied. Most perishable foods including eggs, dairy, products, meat, sea foods, vegetables and fruits may be held in chilling storage for a limited time with little change from their original condition. Enzymatic and microbial changes in the food are not prevented, but are reduced considerably.
Factors to be considered in connection with chilling storage include the temperature of chilling, the relative humidity, air velocity and composition of the atmosphere in the store room and the possible use of ultra-rays or other radiations.
(c) Freezing (- 18 to – 40°C):
At temperature below the freezing point of H2O, growth of microorganisms and enzyme activity are reduced to minimum. Most perishable foods can be preserved for several months. Fruits, vegetables, juices and fleshy foods can be preserved in this method.
(iii) Preservation by Chemicals:
Many chemicals will kill or inhibit the growth of microorganisms, but most of these are not permitted in foods.
A few that are permitted in prescribed low level in certain foods include are as follows:
a. Sodium benzoate and Potassium meta bi-sulphite – Fruits and vegetable products.
b. Ascorbic acid – Milk and milk products, sweets, cheese, wines and pickles, beverages, syrup.
c. Ethyl formate, Ethyl oxide and Propylene oxide – Act as a fumigant against microorganisms in spices, nuts, dried fruits, etc.
(iv) Preservation by High Temperature:
Application of heat to the foods leads to the destruction of microorganisms. The specific treatment varies with the organisms that have to be killed. The nature of the food to be preserved and other means of preservation that may be used in addition to high temperature.
(v) Pasteurisation:
Pasteurisation is a heat treatment that kills part but not all the microorganisms present and the temperature applied is below 100°C. The heating may be by means of steam, hot H2O, dry heat or electric currents and the products are cooled promptly after the heat treatments. The surviving microorganisms are inhibited by low temperature or some other preservative method if spoilage is to be prevented.
Preservative methods used to supplement pasteurisation include:
i. Refrigeration
ii. Keeping out microorganisms usually by packaging the product in a sealed container.
iii. Maintenance of anaerobic conditions as in evacuated, sealed containers.
iv. Addition of high concentration of sugar, as in jam.
v. Presence or addition of chemical preservatives, e.g., the organic acids on pickles.
(a) HTST Method High temperature and short time (above 70° C)
(b) LTHT Method Low temperature and high time or holding method (60 – 70°C)
(c) Heating at about 100°C
By this method all microorganisms are completely destroyed due to high temperature. The time and temperature necessary for sterilisation vary with the type of food. Temperatures above 100°C can only obtained by using steam pressure sterilisers such as pressure cookers and autoclaves.
When processed or raw food material preserved for long duration is called as permanent preservation.
The methods are as follows:
(i) Preservation by Drying:
Microorganisms need moisture to grow so when the concentration of water in the food is brought down below a certain level they are unable to grow. Moisture can be removed by the application of heat as in sun drying or by mechanical drying.
Sun drying is the most popular and oldest method of preservation. In these days, mechanical drying has replaced by sun drying.
This is a more rapid process as artificial heat under controlled conditions of temperature, humidity and air flow is provided and fruits and vegetables, e.g., green peas, cauliflower, mango, etc., are dried to such an extent that the microorganisms present in them, fail to survive.
In this method, juices are preserved in the form of powder. The juice is sprayed as a very fine moist into an evaporating chamber through which hot air is passed.
The temperature of the chamber and the flow of air are, so regulated that dried juice falls to the floor of the chamber in the form of a dry powder. The powder is collected and packed in dry containers, which are then closed airtight. The powder when dissolved in water makes a fruit drink almost similar to the original fresh juice.
(ii) Preservation by Filtration:
Filtration is the only successful method for the complete removal of organisms and its use is limited to clear liquids. The liquid is filtered through a previously sterilised ‘bacteria proof filter made sintered glass, diatomaceous Earth, unglazed porcelain, membrane pads or similar material and liquid is forced through by positive or negative pressure. This method has been used successfully with fruit juices, beer, soft drinks wine and water.
(iii) Preservation of Carbonation:
Carbonation is the process of dissolving sufficient CO2 in water or beverage, so that the product when served gives off the gas as fine bubbles and has a characteristic taste. Carbonation adds to the life of a beverage and contributes in some measure to its tang. Fruit juice beverage is generally bottled with CO2.
Moulds and yeast require O2 for growth and become inactive in the presence of CO2. In ordinary carbonated drinks, the O2 which is normally present in solution in water in sufficient amount to bring about fermentation is displaced by CO2. Although carbonated beverages contain sugar much below 66% the absence of air and the presence of CO2 in them help to prevent the growth of moulds and yeasts.
High carbonation should however, be avoided as it usually destroy the flavour of the juice. The keeping quality of carbonated fruit beverages is enhanced by adding about 0.005% sodium benzoate. The level of carbonation required varies according to the type of fruit juice and type of flavour.
(iv) Preservation by Sugar:
Syrup containing 66% or more of sugar does not ferment.
Sugar absorbs most of the available water with the result that there is very little water for the growth of microorganisms hence their multiplication is inhibited and even those already present die out gradually.
Dry sugar does not ferment. Thus, sugar acts as a preservative by osmosis and not as a true poison for microorganisms. Fruit syrup, jam, jelly, marmalade, preserve, candy, crystallised fruit and glazed fruit are preserved by sugar.
(v) Preservation by Fermentation:
Decomposition of carbohydrates of microorganisms or enzyme is called fermentation. This is one of the oldest method of preservation. By this method, food are preserved by the alcohol or organic acid formed by microbial action.
The keeping quality of alcoholic beverages, vinegar and fermented pickles depend upon the presence of alcohol, acetic acid and lactic acid respectively.
Wines, beers, vinegar, fermented drinks, fermented pickles, etc., are prepared by these processes. 14% alcohol acts as a preservative in wines, because yeast, etc., cannot grow at that concentration. About 2% acetic acid prevents spoilage in many products.
(vi) Preservation by Salt:
Salt at a concentration of 15-25% is sufficient to preserve most products. It inhibit enzymatic browning and discoloration and also acts an antioxidant, salt in the form of brine is used for canning and pickling of vegetables and curing of meat.
Salt has been reported to have the following effects:
a. It causes high osmotic pressure and hence plasmolysis of cells.
b. It dehydrated foods by drawing out and tying up moisture as it dehydrates microbial cells.
c. It ionises to yield the chloride ion, which is harmful to organisms.
d. It reduces the solubility of O2 in the moisture.
e. It sensitise the cell against CO2.
f. It interferes with the action of proteolytic enzymes.
(vii) Preservation by Acids:
Acid conditions inhibit the growth of many microorganisms hence organic acids are added to or allowed to form in foods to preserve them. Acetic (vinegar), citric (lime juice) and lactic acids are commonly used for preservation.
About 2% acetic acid prevents spoilage of many products. Onions are bottled in vinegar with a little salt. Vinegar is also added to pickles, chutneys, sauces and ketchups. Citric acid is added to many fruit squashes, jams and jellies to increase the acidity and prevent mould growth.
(viii) Preservation by Oil and Spices:
A layer of oil on the surface of any food produces anaerobic conditions which prevent the growth of moulds and yeasts. Thus, pickles in which enough oil is added to form a layer at the top can be preserved for long periods.
Spices like turmeric, pepper and asafoetida have little bacteriostatic effects and their ability to prevent growth of other microorganisms is questionable. Different lots of spices vary in effectiveness depending on the source, the freshness and whether they have been stored whole or ground up. Their primary function is to impact their characteristic flavour to the food.
(ix) Preservation by Antibiotics:
Certain metabolic products of microorganisms have been found to have germicidal effect and are termed as antibiotics.
(a) Nisin is an antibiotic produced by Streptococcus lacti, an organism commonly found in milk, curd, cheese band other fermented milk products.
It is non-toxic and has no adverse effect on the sensory qualities of food and is widely used in the food industry especially for preservation of acid foods in which it is more stable.
It is commonly used in canning of mushrooms, tomatoes and milk products. It suppresses the growth of spoilage organisms, mainly the gas producing spore forming bacteria and toxin producing Clostridium botulinum.
(b) Subtilin is an antibiotic obtained from certain strains of Bacillus subtilis is used in preservation of asparagus, corn and peas. It is most effective against gram positive bacteria and spore forming organisms. Canned peas and tomatoes containing 10-20 ppm of subtilin respectively were found to be free of microorganisms.
(c) Pimaricin is an antifungal antibiotic can be used for treating fruits and fruit juices. At present the above three antibiotics are permitted only in such foods as are cooked prior to use and in the process of cooking, the residual antibiotic is expected to be destroyed.
Use of antibiotics along with other sterilising agents including heat and radiation offer good promise.
(x) Preservation by Irradiation:
Sterilisation of food by ionising radiation is a recently developed method of preservation, which has not yet gained general acceptance.
The unacceptable flavour of some irradiated foods and the fear that radioactivity might be induced in such food has come in the way of its greater use. When gamma rays or electron beams pass through foods there are collision between the ionising radiation and food particles at atomic and molecular levels, resulting in the production of ions pairs and free radicals.
The reactions of these products among themselves and with other molecules results in physical and chemical phenomena, which inactivate microorganism in the food. Thus, irradiation of food can be considered to be a method of cold sterilisation, i.e., food is free of microorganism without high temperature treatment.
Ionising radiation can be used for sterilisation of foods in hermetically sealed packs, reduction of the spoilage organisms in the perishable foods delays ripening of fruits, inhibits sprouting of root vegetables and control infestation in stored cereals.
(xi) Preservation by Modified Atmospheric Packing:
To control organisms that require it air is removed. Increasing the level of CO2 concentration in the sealed container helps to prevent the activity of microorganism. Wax coating of cheeses or oxygen impermeable skin tight plastic films can be quite effective.
(xii) Preservation by Antioxidants:
An antioxidant is a substance which when added to fats and fat containing foods prevents their oxidation and thus, prolongs their self-life. Whole someone and palatability, without them fatty foods cannot be stored for any length of time without becoming rancid. Antioxidants used in foods are Butylated Hydroxyanisole (BHA), Butylated Hydroxyl Tolune (BHT), Propyl gallate, thiodiproponic acid, stannous chloride, tocopherol, vitamin-E, SO2 and ascorbic acid.
3. Dehydration and Drying Preservation:
The practice of drying of food stuffs, specially fruits and vegetables for preserving them is very old.
The term ‘Drying and Dehydration’ means the removal of water. The former term is generally used for drying under the influence of non-conventional energy source like sun and wind. If fruits or vegetables are to be sun dried, they or their pieces should be evenly spread in single layer on trays or boards and exposed to the sun. In sun drying there is no possibility of temperature and humidity control.
The hottest days in summer are, therefore chosen so that, the foods dry very fast thus, preventing them from getting spoiled due to souring. Souring or turning acidic is usually due to growth of microorganisms which convert the carbohydrate in the food to acid.
Dehydration means the process of moisture by the application of artificial heat under controlled conditions of temperature, humidity and air flow. In this process a single layer of fruits or vegetables, whole or cut into pieces or slices are spread on trays, which are placed inside the dehydrator. The initial temperature of the dehydrator is usually 43°C, which is gradually increased to 60°-66°C in the case of vegetables and 50-71°C for fruits.
Advantages of Dried/Dehydrated Foods:
Dried foods are in more concentrated from than foods preserved in other ways. They are less costly to produce than canned or preserved food, because of lower labour cost and because of no sugar is required.
Due to reduction in bulk of the product it requires less storage space. The weight of a product is reduced to 1/4th to 1/9th its original or fresh weight and thus the cost of its transport is reduced.
Drying Preservation of Some Vegetables:
(i) Drying Potatoes:
Choose potatoes that are firm and undamaged. Peel the potatoes; wash them under the faucet or in a container with clean water, and cut them in slices about 3 mm thick. Immerse the slices in boiling water, let them cook for 3-5 minutes, rinse them off with clean water, dry them with a clean cloth and place them on a piece of black plastic or on trays to dry for 2 to 3 days in the Sun.
Turn them regularly, about 2 to 3 times per day. The drying process is finished when the potatoes are hard and crumble easily when squeezed in your hand. The dried potatoes have to be soaked in water before they can be consumed.
(ii) Drying Tomatoes:
Use firm, not too ripe, undamaged tomatoes. Wash and then cut them in half or in quarters (or in smaller pieces), and remove the seeds. Blanch the tomato pieces for one minute at 90°C and then allow them to cool off quickly under cold, running water. Once cooled, they have to be immersed for 10 minutes in water to which lemon juice has been added.
Strain and then dry them with a clean cloth. Place the tomatoes on a piece of black plastic and let them dry in the Sun. To make sure that they dry evenly, turn them 2 to 3 times per day. Place them under a shelter in the evenings. After 2 to 3 days they will feel brittle, and the drying process will have been completed.
3. Preservation for Fruit Beverages:
Drinks or beverages are liquids specifically prepared for human consumption. In addition to basic needs, beverages form part of the culture of human society. Despite the fact that most beverages including juice, soft drinks and carbonated drinks have some form of water in them and the word beverage has been recently defined as not referring to water.
In tropical countries like India, fruit beverages provide delicious cold drink during hot summer. Due to their nutritive value they are becoming more popular than synthetic drinks which at present have a very large market in our country.
Synthetic drinks contain only water (about 88%) and total carbohydrate (about 12%) and provide about 48 kcal, whereas fruit based drinks contain vitamins (A, B and C) and minerals (iron, calcium) and provide more calories. Thus, fruit based drinks are far superior to many synthetic drinks. In synthetic (drinks) preparations are replaced by fruit beverages, it would be a boon to the consumers as well as to the fruit growers.
Fruit beverages are easily digestible, highly refreshing, thirst quenching, appetising and nutritionally far superior to many synthetic and aerated drinks. They can be classified into two groups.
(i) Fermented Beverages:
Fruit juices which have undergone alcoholic fermentation by yeasts include wine, champagne, por, sherry, Tokay, muscat, perry, orange wine, berry wine, nira and cider.
(ii) Unfermented Beverages:
Fruit juices which do not undergo alcoholic, fermentation are termed as unfermented beverages. They include natural and sweetened juices, RTS, nectar, cordial, squash, crush, syrup, fruit juice concentrate and fruit juice powder. Barley waters and carbonated beverages are also included in this group.
Preparation and Preservation of Unfermented Fruit Beverages:
(i) Selection of Fruit:
Only fully ripe fruits are selected. Over ripe and green fruits, if used adversely affected the quality of the juice.
(ii) Sorting and Washing:
Diseased, damaged or decayed fruits are rejected or trimmed. Dirt and spray residues of arsenic lead, etc. are removed by washing with water or dilute hydrochloric acid.
(iii) Juice Extraction:
Generally, juice is extracted from fresh fruit by crushing and pressing them. Screw type juice extractors, basket presses or fruit pulper are mostly used.
(iv) Deaeration:
Fruit juices contain some air, most of which is present on the surface of the juice and some is dissolved in it. Most of the air as well as other gases are removed by subjecting the fresh juice to a high vacuum. This process is called deaeration and the equipment used for the purpose is called a deaerator. Being a very expensive method it is not used in India at present.
(v) Straining or Filtration:
Fruit juices always contain varying amounts of suspended matter consisting of broken fruit tissue, seed, skin gums, pectic substances and protein in colloidal suspension. Seeds and pieces of pulp and skin which adversely affect the quality of juice are removed by straining through a thick cloth or sieve.
(vi) Clarification:
Complete removal of all suspended material from juice as in lime juice cordial is known as clarification.
Preparation of Jam, Jelly and Marmalade:
Jam:
Jam is a product made by boiling fruit pulp with sufficient quantity of sugar to a reasonably thick consistency, firm enough to hold the fruit tissues in position. Apple, sapota, papaya, plums, mango, grapes, jack, pineapple, banana, guava and pears are used for preparation of jam.
It can be prepared from one kind of fruit or from two or more kinds. In its preparation about 45% of fruit pulp should be used for every 55% of sugar. The FPO (Food Product Order) specification of jam is 68.55 TSS, (Total Solvable Solids) 45% of fruit pulp and 0.5-0.6% of acid (citric acid) per 100g of the prepared product.
(i) Selection and Preparation of Fruit – Select good quality ripe fruits. Wash the fruits well in cold water. Peel the fruits and remove the stones and cores present. Cut the peeled fruit into small pieces with a stainless steel knife. If the fruit by using pulper.
(ii) Cooking – Cook the mixture slowly with occasional stirring. The fruit pulp should be crushed with a ladle during cooking. Continue cooking till the temperature of the mass reaches 105.5° C.
(iii) Packaging – Fill the hot jam into clean dry sterilised jars. Allow the jam to cool and fix the sterilised lid to the jar. Store in a cool place.
Ripe firm fruits → Washing → Peeling → Pulping (remove seed and core) → Addition of sugar and acid → Boiling (with continuous stirring) → Judging of end point by further cooking upto 105° C or 69% TSS or by sheet test Filling hot into sterilised bittles → Cooling → Waxing → Capping → Storage (at ambient temperature).
(i) Crystallisation – The final product should contain 30-50% invert sugar. If the percentage is less than 30, cane sugar may crystallise out on storage and if it is more than 50 the jam will become a honey like mass due to the formation of small crystals of glucose, Corn syrup or glucose may be added along with cane sugar to avoid crystallisation.
(ii) Sticky or Gummy Jam – Because of high percentage of TSS, jams tend to become gummy or sticky. This problem can be solved by addition of pectin or citric acid or both.
(iii) Premature Setting – This is due to low and high pectin content in the jam and can be prevented by adding more sugar.
(iv) Surface Graining and Shrinkage – This is caused by evaporation of moisture during storage of jam. Storing in a cool place can reduce it.
(v) Microbial Spoilage – Moulds may spoil the jam during storage, but they are destroyed if exposed to less than 90% humidity. Hence, jams should be stored at 80% humidity. It is also advisable to add 40 ppm SO2 in the form of KMS or 200 ppm of benzoic acid.
A jelly is a semi-solid product prepared by boiling a clear, strained solution of pectin containing fruit extract, free from pulp, after the addition of sugar and acid. A perfect jelly should be transparent, well set but not too stiff and should have the original flavour of the fruit. It should be of attractive colour and keep its shape when removed from the mould. It should be firm enough to retain a sharp edge, but tender enough when it is pressed.
It should not be gummy, sticky or syrupy or have crystallised sugar. The product should be free from dullness with little or no syneresis (weeping) and neither tough nor rubbery. The FPO specification for jelly is the final product should have 65% solids, 45% fruit extract and 0.5-0.75% acid.
Guava, sour apple, plum, karonda, wood apple, papaya and jack fruit are rich in pectin and generally used for preparation of jelly. Pineapple, strawberry grapes, etc., can be used but only after addition of pectin powder, because these fruits have low pectin content. Preparation of jelly is similar to that of jam.
Fruits (firm not over ripe ) → Washing → Cutting into thin slices Boiling with water (1 1/2 times the weight of fruits for about 20-30 minute) → Addition of citric acid during boiling (2 g/kg of fruit) → Straining of extract → Pectin test (for addition of sugar) → Addition of sugar → Boiling → Judging of end point (sheet / drop / temp test) → Removal of scum or foam (one teaspoonful of edible oil added for 45 kg sugar) → Addition of colour and remaining citric acid → Filling hot into clean sterilised bottles → Waxing (paraffin wax) → Capping → Storage at ambient temperature.
Important Considerations in Jelly Making:
Pectin, acid, sugar (65%) and water are the four essential ingredients. Pectin test and determination of end point of jelly formation are very important for the quality of jelly.
i. Addition of too much sugar
ii. Lack of acid or pectin
iii. Cooking below the end point
iv. Cooking beyond the end point
v. Prolonged cooking
vi. Use of non-clarified juice or extract
vii. Use of immature fruits
viii. Over cooking
ix. Over cooling
x. Non-removal of scum
xi. Faulty pouring
xii. Premature gelation-due to excess of pectin in the extract
Syneresis or Weeping of Jelly:
The phenomenon of spontaneous exudation of fluid from a gel is called syneresis or weeping.
This may be due to:
i. Excess of acid
ii. Too low concentration of sugar
iii. Insufficient pectin
iv. Premature gelation
v. Fermentation
vi. Storage place was too warm
vii. A layer of paraffin that was too thick
This is a fruit jelly in which slices of the fruit and its peel are suspended. The term is generally used for products made from citrus fruits like oranges and lemons in which shredded peel is used as the suspended material.
Citrus marmalades are classified into two parts:
i. Jelly marmalade
ii. Jam marmalade
Pectin extract- 1 L
Sugar- 750 g
Shredded peel- 62 g
i. Jelly Marmalade – It is prepared from the clarified pectin extract.
ii. Jam Marmalade – The method of preparation is practically the same as that for jelly marmalade. In this case, the pectin extract of fruit is not clarified and the whole pulp is used. Sugar is added according to the weight of fruit, generally in the proportion of 1:1. The pulp sugar mixture is cooked till the TSS content reaches 65%.
Ripe fruits → Washing → Peeling outer yellow portion thinly → Cutting yellow portion into fine shreds → Cutting of 0.3-0.45 cm thick slices of peeled fruit or crushing into pulp in a grater → Boiling straining the extract → Testing for pectin content → Addition of sugar → Cooking to 103-105°C → Addition of prepared shreds Boiling till jellying point → Testing for end point → Cooling → Flavouring → Filling in sterilised bottles → Sealing Storage at ambient temperature.
Browning during storage is very common which can be prevented by addition of 0.09 g of KMS per kg of marmalade and not using in containers.
KMS dissolved in a small quantity of water is added to the marmalade while it is cooling. KMS also eliminates the possibility of spoilage due to moulds.
Preparation of Candied Fruits and Glazed Fruits:
Candied Fruits/Vegetables:
A fruit/vegetable impregnated with cane sugar or glucose syrup and subsequently drained free of syrup and dried is known as candied fruit/vegetable.
The most suitable fruits for candying are amla, karonda, pineapple, cherry, papaya, apple, peels of orange, lemon, grape and ginger, etc. The FPO specifications for candied fruits are TSS (Total Soluble Solids) – 75 %, total sugar- 70% and reducing sugar 25%.
The process for making candied fruit is practically similar to that for preserves. The only difference is that the fruit impregnated with syrup having a higher percentage of sugar – 75%.
The syrup left over from the candying process can be used for candying another batch of the same kind of fruit after suitable dilution, for sweetening chutneys, sauces and pickles and vinegar making.
Covering of candied fruits/vegetables with a thin transparent coating of sugar, which imparts them a glossy appearance is known as glazing. Cane sugar and water are boiled in a steam pan at 113-114° C and the scum is removed as it comes up. Thereafter, the syrup is cooled to 93° C and rubbed with a wooden ladle on the side of the pan when granulated sugar is obtained.
Dried candied fruits are passed through this granulated portion of the sugar solution, one-by-one, by means of fork and then placed on trays in a warm dry room. They may also be dried in drier at 49° C for 2-3 h. When they become crisp, they are packed in airtight containers for storage.
Crystalised Fruits/Vegetables:
Candied fruits/vegetables coated with crystals of sugar, either by rolling in finely powdered sugar or by allowing sugar crystals from a dense syrup to deposit on them are called crystallised fruit/vegetable.
The candied fruits are placed on a wire mesh tray which is placed in a deep vessel. Cooled syrup is gently poured over the fruit so as to cover it entirely. The whole mass is left undisturbed for 12-18 h during which a thin coating of crystallised sugar is formed. The tray is then taken out carefully from the vessel and the surplus syrup dried off. The fruits are then placed in a single layer on wire mesh trays and dried at room temperature or at about 49° C in driers.
Preparation and Preservation of Pickles:
The preservation of food in common salt or in vinegar is known as pickling. It is one of the most ancient methods of preserving fruits and vegetables. Pickles are good appetizers and add to the palatability of a meal. They stimulate the flow of gastric juice and thus help in digestion.
Raw Materials Used in Pickling:
1. Salt:
Free from impurities and salts such as lime, iron, magnesium and carbonates.
2. Vinegar:
Vinegar of good quality should contain at least 4% acetic acid, synthetic vinegar or low quality vinegar are not suitable for pickle preparations. Usually, malt or cider vinegar is used. In order to ensure good keeping quality pickle, the final concentration of acetic acid in the pickle should not be less than 2%. Acetic acid is also used because, it is highly concentrated.
3. Sugar:
Used in the preparation of sweet pickles should be of high quality.
4. Spices:
Spices are added practically to all pickles, the quantity added depending upon the kind of fruit or vegetable taken and kind of flavour desired. The spices generally used are bay leaves, cardamom, chilies, cinnamon, cloves, coriander, dill herb, ginger, mace mustered, black pepper, cumin, turmeric, garlic, mint fenugreek, asafetida, etc.
5. Water:
Only potable water should be used for the preparation of brine. Hard water contains salts of Ca, Na, Mg, etc., which interfere with the normal salt curing of the vegetable. If hard water is to be used, a small quantity of vinegar should also be added to the brine to neutralise its alkalinity. Iron should not be present in the water in any appreciable quantity as it causes the blackening of the pickle.
i. Bitter Taste:
Use of strong vinegar or excess spices or prolonged cooking of spices imparts a bitter taste to the pickle.
ii. Shriveling:
It occurs when vegetables are placed directly in a very strong solution of salt or sugar or vinegar. Hence, a dilute solution should be used initially and its strength gradually increased.
iii. Scum Formation:
When vegetables are cured in brine, white scum always form on the surface due to the growth of wild yeast.
Hence, it is advisable to remove scum as soon as it is formed. Addition of 1% acetic acid helps to prevent the growth of wild yeast in brine, without affecting lactic acid formation.
iv. Softness and Slipperiness:
Due to inadequate covering with brine or use of weak brine.
v. Cloudiness:
In some vegetables the acetic acid cannot penetrate deep enough into its tissues to inhibit the activity of bacteria and other microorganisms, present in them. Fermentation start from inside the tissues, rendering the vinegar cloudy. This microbial activity can only be checked by proper bring cloudiness may also be caused by use of inferior quality vinegar or chemical reaction between vinegar and minerals.
vi. Blackening:
It is due to the iron in the brine or in the process equipment reacting with the ingredients used in pickling. Certain microorganisms also cause blackening.
Preservation of Pickle by Salt, Vinegar and Oil:
1. Preservation of Pickle by Salt:
Salt improves the taste and flavour and hardens the tissues of vegetables and controls fermentation. Vegetables do not ferment when they are packed with a large quantity of salt, bringing its final concentration in the material from 15-20%. At this high salt concentration, mould and even lactic acid forming bacteria do not grow. This method of preservation is applicable only to vegetable which contain very little sugar, because sufficient lactic acid cannot be formed by fermentation to act as preservative. Some fruits like lime, mango, etc., are also preserve with salt.
Lime Pickle:
Ingredients:
i. Lime – 1 kg
ii. Salt – 200 g
iii. Red chilli powder – 15 g
iv. Cinnamon, cumin, cardamom and black pepper each – 10 g
v. Cloves – 5 nos.
Lime → Washing → Cutting into four pieces → Squeezing out juice from 1/4 amount of fruit → Mixing spices and salt with juice → Mixing with lime pieces → Filling in jars → Covering with lid → Keeping in Sun for 4-6 days → Storage at ambient temperature.
2. Preservation to Pickle by Vinegar:
In vinegar pickles, vinegar acts as a preservative. The final concentration of acids in the finished pickle should not be less than 2%. To avoid dilution of vinegar below this strength by the H2O liberated from the tissues, the vegetables or fruits are generally placed in strong vinegar of about 10% acidity for several days before final packing. This treatment helps to expel the gases present in the intercellular spaces of vegetable tissues.
Papaya, pears, onion, garlic, chilli, mango and cucumber pickles are prepared in this method.
For example:
Ingredients:
i. Cucumber – 1 kg
ii. Salt-200 g
iii. Red chilli powder -15 g
iv. Cardamon, cumin, black pepper each – 10 g
v. Cloves – 6 nos.
vi. Vinegar – 750 mL
Cucumber → Washing → Peeling → Cutting into 5 cm round pieces → Mixing with salt → Filling in jar → Standing for 6-8 h → Draining of H2O → Adding spices and vinegar → Keeping for a week → Storage
3. Preservation of Pickles with Oil:
The fruit or vegetable should completely immersed in the edible oil. Cauliflower, lime, mango, amla, karonda, bittergourd, brinjal, turnip pickles are prepared from this method.
For example:
Ingredients:
i. Green chilli – 1 kg
ii. Salt – 150 g
iii. Mustard – 100 g
iv. Lime juice – 200 mL or
v. Amchur powder — 200 g
vi. Fenugreek, cardamom, turmeric, cumin each – 15 g
vii. Mustard oil – 400 mL
Green chillies → Washing → Drying → Making incision → Mixing all spices in a little lime juice → Mixing with chillies → Filling into jar → Adding lime juice and oil → Keeping in sun for a week → Storage
4. Preserving Vegetables:
Preserving Vegetables with Salt and Vinegar:
Adding salt is one of the oldest way to preserve food, except fruit, especially in areas that have easy access to inexpensive salt. Since, salt absorbs much of the water in food, it makes it difficult for microorganisms to survive. There are two salting methods. One uses a lot of salt and the other only a small amount. The disadvantage of using a lot of salt is that it has a very negative impact on the taste of the food.
To overcome this problem, the food can be rinsed or soaked in water before it is eaten, but this also decreases the nutritional value of the food. It is therefore advisable to use a lot of salt only when there is a surplus of fresh vegetables and no other preservation method is possible.
The use of a small amount of salt is in itself not enough to prevent the growth of bacteria, but it does result in the development of a certain kind of acid-producing bacteria that limits the growth of other bacteria.
One example of a product made in this way is sauerkraut, which has a high nutritional value. Another way to preserve vegetables is by adding vinegar.
There are several possible methods of preserving fruit, i.e., canning, sterilising and drying. A mixture of two or more kinds of fruit often gives a better, more rounded taste in the final product. Apricots and peaches combine very well with orange or grapefruit juice. Orange and grapefruit juices can also be mixed. Pineapple is often mixed with orange, grapefruit, or apricot juice.
The juices are best mixed before preserving, not just before use. Choose the proportion of the fruit in the mixtures according to your individual taste. The proportions have no effect on the shelf-life of the product.
Mouldy fruit increases the chance of spoilage and of causing food poisoning. Overripe fruit results in a tasteless or sometimes slightly musty-tasting product. All materials with which the fruit comes into contact, such as knives, pots, kettles, cans, pans and bottles, should be made of stainless steel, glass, undamaged enamel or good-quality plastic. Avoid using aluminium or galvanised tools and kettles, as the acid in the fruit will attack these.