Download In this method food material is cut into small pieces and a large

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.
2.
3.
4.
5.
Contamination of food by Micro-organisms. Ex. Bacteria, Virus, Fungi
Decomposition of food items due to insect pests
Improper storage of food by using unclean vessels, impure water etc
Storage of food materials in unprotected environments.
Presence of more moisture content and keeping the food open to Air &
insects
C.botulinum
Rhizopus
Viruses
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
3 tier drier
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
DRY FISH
Banana Powder
Vegetable Powder
Sun Drier
Freeze Dryier
3. Smoking: Heat form smoke removes moisture.
Ex.Fish,Meat
Smoking Meat
Smoking Fish
4. Salting: Salted Vegetable pieces are mixed with
oil to preserve.
Ex.Pickles
Pickles
5. Freezing: Microbial growth is retarded in low
temperatures
6. High Temperature: Destruction of microbes.
Ex. Milk Pasteurisation
Frogen Vegetables
7. Canning: Quickly cooked food stored in sterile containers
and sealed, again heated to kill microbes.
Tinned Food
Ex. Vegetables, Meat, Fishes and sweets.
Canned mixed fruit
Canned Peaches
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
Microwave oven
Killed Insects