food spilage and wastage(science)
DESCRIPTION
K J Somiaya college of education. PPT presentation of CAPTRANSCRIPT
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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
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Food Spoilage
•Loss in nutritive value•Creates dangerous toxins•Loss in fresh appearance
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Definition
Food Spoilage can be defined as undesirable
changes occurring in food, making it unfit &
unacceptable for human consumption.
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Types of undesirable changes
a) Change in colourb) Change in smellc) Change in consistencyd) Change in Texturee) Change due to mechanical
damage
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Factors causing Food spoilage
• Intrinsic Factors•Extrinsic Factors
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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.
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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.
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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.
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3. Micro-organism :- Growth & Multiplication of micro-
organisms leads to food spoilage.
Example : Yeast, bacteria etc contaminate the food which
cause food poisoning.
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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.
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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.
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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.
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Food Preservation
A process by which certain foods like fruits & vegetables are prevented from getting spoilt for a long period of time.
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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.
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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.
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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.
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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.
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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.
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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.
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Evaluation1. Define Food spoilage
Ans: Food spoilage can be defined as undesirable changes occurring in food, making it unfit & unacceptable for human
consumption.
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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.
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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
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