Methods of Food Preservation: All food commodities

It has various general methods of food preservation

1. Methods of Food Preservation Dr. Roshan Lal Assistant Professor Department of Home Science (Food Technology) Lakshmibai College (University of Delhi)

2. Introduction: Food preservation is essential in India due to the country's high population (food security), diverse climate, significant food spoilage rates and consumer convenience.  It helps to reduce post harvest waste , extend shelf life, ensure food safety and allows for access to a variety of foods year-round . Food Preservation: Food preservation is a kind of processing techniques which are used to increase the shelf-life of the food. Naturally food have limited shelf-life, but with the use of various processing and preservation methods the self-life can be extended from few days to several months. Food preservation is very essential, as the degradation of quality takes place just after manufacturing/ slaughtering/ harvesting of food.

3. Need of food preservation: 1. Extend the shelf-life of food: 2. Development of food products: 3. Establish food security 4. Utilize seasonal fruits and vegetables 5. Facilitate transportation of food 6. Retain freshness and quality of food

4. Food Spoilage: Food spoilage is the metabolic process that causes foods to becomes unfit for human consumption due to changes in its physical, chemical and microbial properties .   Tomato Rice Bread

5. Causes of Food Spoilage: 1. Microorganisms Bacteria Yeast + Mold= Fungi These microorganisms penetrate in the food and causes spoilage by molding, fermentation and putrefaction. 2. Chemical reaction Oxidative rancidity is a form of food spoilage where fats react with oxygen, leading to undesirable changes in flavor, color and texture. 3. Enzymes Enzymes found naturally in the food and helps in the many reaction such as ripening, colour and texture development, but the uncontrolled activity of enzymes leads to fruits and vegetable spoilage by over ripening, softening of tissue and development of off flavour . 4. Insect & Rodents Insects & Rodents damage the food which leads to spoilage of food, moreover they also spoil food by dropping their excreta.

6. Factors responsible for food spoilage: Temperature: The medium temperature is very much responsible for food spoilage, whereas storage of food at very low and very high temperature prevent food spoilage. The intermediate temperature helps microorganism to multiply faster and increase activity of enzymes. 2. Moisture: High moisture content also leads to microbial growth and enzymatic reaction. 3. Air: Atmospheric air which contains oxygen are responsible for aerobic microbial growth and faster oxidative reaction.

7. Perishability of Food: On the basis of perishability and shelf-life, foods are classified as: 1. Perishable foods: These foods spoil quickly, often within few hours or days if not treated /refrigerated or frozen.   Proper storage and handling are crucial to prevent spoilage and maintain food safety.  Examples: meat , poultry, fish, dairy products and fresh fruits and vegetables.  2. Semi-perishable foods: These foods have a longer shelf life than perishable foods but still require proper storage to prevent spoilage.  They can last for weeks or months if stored correctly, such as in a cool, dry place.  Examples: potatoes , nuts, pasteurized butter and eggs.  3. Non-perishable foods: These foods have a very long shelf life and do not require refrigeration.  They are often preserved by canning, drying and other methods to remove moisture. Examples: cereals, canned f oods, rice, beans and dried fruits. 

8. General R ules for Food Preservation: The quality of selected raw material must be good. The appropriate method of preservation must be selected according to the food material. The process should be profitable and advantageous for the producers and consumers. The product must be hygienically processed to keep it uncontaminated. Packing of processed food must be adequate to maintain the quality of food.

9. Methods of Food Preservation Dehydration and drying Alteration of temperature (use of heat and cold) Use of sugar, salt, vinegar and oil Chemical preservatives Irradiation

10. Dehydration Removal of H 2 O Convenient to pack, transport & store Reduce microbial growth and prevent spoilage Food can be reconstituted Sun drying is most economical process For maintaining the quality, some another techniques (Blanching) can also be applied with dehydration Precautions: Select the food which can be dried to low moisture content Process the food for effective and quick drying (increase surface area) Protect from birds, insects, dust and other contaminants Proper storage (Air and moisture proof containers) after drying

11. Altering temperature: 1. Low Temperature Preservation: The low temperature prevent the growth of microorganisms (It does not kill the microorganism) Refrigeration: Temperature ranges from 4-7 o C The food remains in unfrozen condition It slow down the growth of microorganism Generally used in domestic practices for storage of milk, fruits, vegetables etc. Cold Storage: It generally used at industrial level for bulk storage of fruits and vegetables. Temperature ranged from 0 to 10 o C The food may or may not converted in frozen state

12. Freezing : The water molecules available in foods is converted into ice, which becomes unavailable for microorganisms It also used at industrial level for bulk storage of meat, fish, fruits, vegetables etc. The shelf-life can be extended up to years The product must be thaw after removing from freezers, not to put again in the freezers

13. 2. High Temperature Preservation : In high temperature preservation microorganisms are killed with the used of heat 1. Canning: Canning is a method of food preservation in which food is processed , sealed in an airtight container and thermally treated. This extends the shelf-life up to years Examples: Canned fruits, vegetables, meat, fish etc. 2. Sterilization: It is a complete destruction of microorganism by the use of high temperature (above 100 o C) Example: sterilized milk 3. Cooking: Cooking is a domestic practice in which high temperature is used to process the food (pressure cooking, boiling, frying, microwave cooking) 4. Pasteurization: It is a thermal process in which heat is used for shorter duration to kill the pathogenic microorganism. Example: Pasteurized milk and juice

14. Use of Salt, Sugar, Vinegar and oils (Primary Preservatives): Salt and sugar act as strong osmotic regulator, which removes out the water from fruits and vegetables when used in proper concentration. The water becomes unavailable for microorganisms, hence growth of microorganisms retarded. Sugar acts as preservatives in Jam, Jelly, Squashes etc. Salts acts as preservatives in pickles Vinegar (Acetic acid): It is highly acidic, which reduces the pH of food and at low pH most of the microorganisms can’t grow. Used in the preservation of pickles. Oils: T he oil creates a protective barrier which prevents air from reaching the ingredients and reducing the risk of oxidation and microbial growth. Used in the preservation of pickles .

15. Chemical Preservatives: These are the chemical substances which reduces the rate of spoilage in foods. These are mainly useful where other preservation method is not effective / applied ( e.g : preservation of fruit juices, squashes etc.) Precautions to be taken: It should be used in specified permitted safe level. It should be effective and non toxic It should have antimicrobial properties It should not impart any off- flavour to the food Sodium benzoate Potassium metabisulphite / SO 2 It is a salt of benzoic acid. Used in preservation of colured fruit juice Amount varies from 0.06 to 3% It is used as a source of SO 2 More effective as gas can dissolve effectively Amount generally used is 0.3% in squashes

16. Food irradiation: It is a novel technique of food preservation in which two types of rays are generally used to kill the microorganisms: Gama rays Ultraviolet rays Advantages: It can sterilize the food without heating The property & nutritional value retains in the food It is more useful in packed foods, grains, spices and in inhibition of sprouting in potatoes, onions etc. Disadvantage: It is an expensive technique Caution needs to be taken during the use

17. Common preservation methods for daily use at home 1. Drying and dehydration: Making potato chips Drying of fenugreek & peppermint leave Making papad 2. Pickling & Fermentation: Makings various kinds of pickles (Lemon, mango, green chili, carrot etc.) Making of Sauerkraut and kimchi 3. Preserve: Development of Amla Murrabba Making of ginger candy/ pineapple candy Making of Aam Panna 4. Refrigeration & Freezing: Storage of milk, butter, paneer , fruits & vegetables in refrigerator Freezing of peas & carrot 5. Cooking: Pressure cooking and boiling of different vegetables Frying of various dishes

18. Thanks