Why should we preserve the food? To make the food available through out the year Ex.Paddy. Mango, Tamarind etc. Transport to distant places makes it easy Ex. Apples, Mangoes and grapes To avoid wastage of food

What are the main reasons for spoilage of food? 1.Contamination of food by Micro-organisms. Ex. Bacteria, Virus, Fungi 2.Decomposition of food items due to insect pests 3.Improper storage of food by using unclean vessels, impure water etc 4.Storage of food materials in unprotected environments. 5.Presence of more moisture content and keeping the food open to Air & insects C.botulinumRhizopusViruses C.tetani

Methods to reduce water content in food: 1.Drying the moist food items, fruits,fish,prawn etc in hot sun 2.Smoking food reduces moisture content of fishes 3.Mechanical dehydrators, spraydriers etc. can dehydrater 4.Soaking the food pieces in salt and sun drying Spraydrier Dehydrators Sun drying

Principle involved in preservaion by Salting : 1.In this method food material is cut into small pieces and a large quantity of Salt is added to it. 2. Thus the water present in the food material comes out. 3.The external moisture that is present is removed by drying in sun. 4.Dry salting is used in India for the preservation of tamarind, raw mango, amla, fish and meat Conditions congenial for growth of Bacteria and Fungi: 1.Bacteria grow rapidly if the food is stored at the temperature between 20˚C-40˚C. 2.Fungi grow rapidly if the food is stored at the temperature between 20˚C-30˚C. 3. Fungi grow in warm,dark and damp conditions

METHODS OF FOOD PRESERVATION: 1.Drying: Least expensive method used in tropical countries like India Ex: Vegetables- Beans, Peas, Potatoes, etc. Fruits- Dates, Grapes, Raw Mangoes Fishes, Grains, Pulses and their products. 2. Mechanical Drying: Used in Industries, electrical Ovens are used to dry food i) Dehydrators: Green Peas, onions,Soup mixes ii) Spray Drying: Milk powders, Baby foods, Boost,Complan etc iii) Freeze Drying: Fresh vegetables, Meat, Fishes 3 tier drier DRY FISH Banana PowderVegetable PowderSun DrierFreeze Dryier

3. Smoking: Heat form smoke removes moisture. Ex.Fish,Meat Smoking Meat Smoking Fish Pickles 4. Salting: Salted Vegetable pieces are mixed with oil to preserve. Ex.Pickles

5. Freezing: Microbial growth is retarded in low temperatures 6. High Temperature: Destruction of microbes. Ex. Milk Pasteurisation 7. Canning: Quickly cooked food stored in sterile containers and sealed, again heated to kill microbes. Ex. Vegetables, Meat, Fishes and sweets. Frogen Vegetables Canned Peaches Canned mixed fruit Tinned Food

PASTEURISATION: 1.Milk is heated to 72˚C for 15 Sec. 2.Then milk is cooled to 10˚C. 3.The high temperature kills Bacteria. 4.Then milk is sealed in sterile bottles/sachets. CONTROL OF RATS BY CHEMICALS: 1.Rats can be controlled by mechanical & chemical methods. 2.Chemicals like Zn. phosphide is mixed with Flour, sugar and oil to form a paste. 3.The paste is made into small balls. 4.At first the rats are habituated to eat these balls without the poisonous chemical 5.After a week these balls containing Zn. phosphide are taken by rats and killed.

FUMIGATION: 1.Insect pests in food items are controlled by spraying and fumigation. 2.Pests present in grain and storage area are killed by Ethylene Dibromide(EDB) or Alluminium Phosphate. 3. EDB and Al.phosphate are kept in Godowns with closed doors. 4. After a week, the dead insects are removed. Alluminium Phosphide fumigator Killed Insects Microwave oven