PRINCIPLES OF FOOD PRESERVATION SMG

A Brief Account of Principles of Food Preservation

1. PRINCIPLES OF FOOD PRESERVATION Dr. Saji Mariam George Associate Professor Assumption College Autonomous Changanacherry

2. PRINCIPLES OF FOOD PRESERVATION Prevention or delay of microbial decomposition Killing the microorganisms Prevention or delay of self – decomposition of the food Prevention of damage by insects, animals, mechanical causes etc.

3. 1.Prevention or delay of microbial decomposition a). Keeping out microorganisms (Asepsis)- state of being free from spoilage microbes – bacteria , fungi etc. Egs : Shells of nuts, almonds, walnuts ,egg etc. Skins of fruits – banana, orange Packaging – prevents the entry of microbes Use of clean vessels, hygienic surroundings – help to prevent spoilage of milk during collection and processing by keeping out microorganisms .

4. b). By removal of microorganisms by Filtration For the preservation of clear liquids – water, fruit juices, beer, soft drinks etc. Use “ bacteria proof” filters made up of asbestos pad, unglazed porcelain – candle filters.

5. Microbes can also be removed by Centrifugation(Treatment of drinking water) Washing raw foods Trimming away spoiled portions of food.

6. c). Hindering the growth and activity of microorganisms Use of low temperature Preservation of food at refrigeration temperatures – increases the lag phase of many microorganisms and thus prevents their growth in foods.

7. ii) Drying Sun drying Mechanical drying Binding the moisture with addition of sugar or salt and making it unavailable to microbes. Water content of food is reduced- below a certain level - microorganisms can not grow.

8. iii) Maintenance of anaerobic conditions prevent the growth of aerobes. e.g. Canned food – canned pea, mush rooms, baby corns etc. Fruit juices in airtight containers – Care should be taken to kill or inactivate anaerobic bacteria ( Clostridium botulinum ) and their spores.

9. iv) Use of chemical preservatives. Sodium benzoate Potassium metabisulphite Sorbic acid Calcium propionate Antioxidants –prevent rancidity (development of off- flavours in edible oils) e.g. Butylated Hydroxy Anisole (BHA), Butylated Hydroxy Toluene (BHT), Lecithin.

10. 2. Killing the Microorganisms. a). Heat - Exposing food to high temperature kills most of microorganisms . b). Irradiation - should be used with caution Use of UV lamps to sterilize knives in bakeries α, ß and Ƴ rays for preservation of vegetables , fruits, sea foods etc.

11. 3. Prevention or delay of self – decomposition of food a). Blanching Mild heat treatment given to vegetables by dipping them in hot water or exposing them to steam for a few minutes. Heat inactivates the enzymes present in the vegetables and prevent self decomposition of food.

12. b). Prevention of Oxidation Rancidity ( development of unpleasant odour ) of fats and oils by oxidation – prevented by antioxidants. Eg . Butylated Hydroxy Anisole (BHA) Butylated Hydroxy Toluene (BHT)

13. THANK YOU