Content

• Definition of Food Spoilage• Types of undesirable changes• Factors causing Food Spoilage• Factors affecting growth of Micro-

organism• Definition of Food Preservation• Principles of Food Preservation• Methods of Food Preservation

Food Spoilage

•Loss in nutritive value•Creates dangerous toxins•Loss in fresh appearance

Definition

Food Spoilage can be defined as undesirable

changes occurring in food, making it unfit &

unacceptable for human consumption.

Types of undesirable changes

a) Change in colourb) Change in smellc) Change in consistencyd) Change in Texturee) Change due to mechanical

damage

Factors causing Food spoilage

• Intrinsic Factors•Extrinsic Factors

Intrinsic Factors

• Enzymatic reactions :- Enzymes present in food starts degrading the food resulting into spoilage of Food.

example - blackening of bananas & apples.

• Chemical reactions : - Certain chemical reactions takes place within the food which leads to food spoilage.

example – cut meat kept for long time.

Extrinsic Factors1. Mechanical damages :- Physical

damages due to improper handling.example : If food is handled improperly while plucking, transporting, drying, preserving, etc.it may cause bruising of Food tissues.

2. Chemical reactions due to contact with metal :- Foods of acidic or alkaline nature may react with metal container leading to undesirable change.

Example : Butter milk kept in brass vessel.

3. Micro-organism :- Growth & Multiplication of micro-

organisms leads to food spoilage.

Example : Yeast, bacteria etc contaminate the food which

cause food poisoning.

4. Insects, rodents, birds :- Foods are mechanically damaged by insects, rodents, birds, etc.

Example : The holes on surface of tomatoes, cucumber, brinjal indicate that they are harboring larvae of insects.

Factors affecting growth of Micro-organism

1. Nutrients in food – presence of easily utilizable nutrients encourage faster growth of micro-organism.

2. Water content – Micro-organism require a lot of water for their growth.

3. Physical, environmental Factors – Temperature, PH value of food influence microbial activity.

4. Availability of Oxygen – Most of the micro-organism require

oxygen for their growth such micro-organism are called ‘Aerobic’ micro-organisms and

those which do not require oxygen for their growth are called ‘Anaerobic’ micro-organisms.

Food Preservation

A process by which certain foods like fruits & vegetables are prevented from getting spoilt for a long period of time.

Principles of Food Preservation1.Preventing the spoilage by micro-

organisma)Keeping out micro-organism

Example : Covering the food, packaging or removing the spoiled food.

b)Removing micro-organism Example : If you want to preserve green leafy vegetable you have to remove the water from the leaves.

c) Inhibiting the growth of micro-organismExample : Drying, lowering or increasing temperature, salting or adding too much of sugar or other preservatives.

d) Killing of micro-organism Example : Boiling, cooking, pasteurization.

2. Preventing self decomposition of Food

a) Destroying enzymes in Food : Enzymes found in food can be inactivated by changing their conditions such as temperature & moisture.

b) Preventing auto-oxidation : by adding antioxidants.

3. Removal of insects, rodents, birds, etc : By proper storage, use of permissible insects repellants.

Methods of Food Preservation

1. Keeping out of micro-organism : Cleanliness, use of clean water, utensils, covering & packaging.

2. Use of High temperature : Heating, boiling, cooking.

3. Use of low temperature :

• Refrigeration 4°C to 7°C

• Cold storage -1°C to -4°C

• Freezing -18°C or below

4. Drying : Dry food grains remain unspoiled for long period under proper storage.

5. Preservatives :

There are 2 types of Preservatives :

• Natural Preservatives - Salt, sugar, vinegar, acid salts etc.

• Chemical Preservatives - Sodium chloride, sodium benzoate, citric acid.

6. Preservation by irradiation - Ionizing radiation such as gamma rays & cathode rays can kill the micro-organism in food.

Evaluation1. Define Food spoilage

Ans: Food spoilage can be defined as undesirable changes occurring in food, making it unfit & unacceptable for human

consumption.

2. What are the extrinsic factors causing Food spoilage

Ans: Extrinsic Factors :

a) Mechanical damage

b) Chemical reactions due to contact with metal

c) Micro-organisms

d) Insects, rodents, birds, etc.

3. What are the methods of Food Preservation

Ans:

a) Keeping out of micro-organisms

b) Use of high temperature

c) Use of low temperature

d) Drying

e) Preservatives

f) Irradiation