BANARAS HINDU UNIVERSITY

PRESENTATION ON PRINCIPLES OF FOOD PRESERVATION.

GUIDED BY- PRESENTED BY-Dr. Akhilendra verma Sarita kumari singh ID No.- R-12029 B.Sc.(Ag.) IV

* PRINCIPLES OF FOOD PRESERVATION *

1.REMOVAL OF MICROORGANISM:- It is usually achieved by filtration.

Commonly used for water, beer, wine, juices, soft drinks, and other liquid.

2. LOW TEMPRATURE:-

Cooling preserves food by slowing down the growth and reproduction of micro organisms and action of enzymes that cause food to rot.

Freezing is also the most commonly used process, both commercially and domestically, for preserving a very wide range of foods.

Refrigeration at 5 degree celsius retards but not stop microbial growth.

Cold stores provide large volume, long term storage.

3.CANNING:- Food items are protected from outer environment by canning. Food heated in special containers to 115 degree celsius for 25-100 min., it kills spoilage microbes, but not necessarily all microbes in food.

4. PASTEURIZATION:- Pasteurization is a process, named after scientist Louis Pasteur, that applies heat to destroy pathogens in foods. Different pasteurization procedures heat the product for different lengths of time. Shorter heating times result in improved flavour. The pasteurization process is based on the use of one of following time & temperature relationship:-1. HIGH TEMPERATURE SHORT TIME TREATMENT (HTST):-

This process uses higher heat for less time to kill pathogenic bacteria.

2. LOW TEMPERATURE LONG TIME TREATMENT (LTLT):- This process uses lower heat for a longer time to kill pathogenic bacteria, such as milk pasteurization at 63 degree celsius for 30 minutes.

TABLE:Temperature Time Pasteurization Type63ºC (145ºF)*

30 minutes Vat Pasteurization

72ºC (161ºF)*

15 seconds High temperature short time Pasteurization (HTST)

89ºC (191ºF)1.0 second Higher-Heat Shorter Time (HHST)

90ºC (194ºF)0.5 seconds Higher-Heat Shorter Time (HHST)

94ºC (201ºF)0.1 seconds Higher-Heat Shorter Time (HHST)

96ºC (204ºF)0.05seconds Higher-Heat Shorter Time (HHST)

100ºC (212ºF)

0.01seconds Higher-Heat Shorter Time (HHST)

138ºC (280ºF)

2.0 seconds Ultra Pasteurization (UP)

5. REDUCED WATER AVAILABILITY:- It is one of the oldest techniques used to hamper the decomposition of products. Water removal, freeze drying, use of spray dryers or heating drums decrease water availability. Vegetables and fruits are naturally dried by the sun and wind, but “still houses” were built in areas that did not have enough sunlight to dry things, a fire would be built inside building to provide the heat to dry the various fruits, vegetables and herbs.

6.CHEMICAL BASED PRESERVATION:- This includes addition of chemicals i.e. inhibitory compounds. example- organic acids, nitrates, sulfur dioxide, etc.

7.IRRADIATION:- Use of ionizing (gamma rays) and non ionizing (u v rays). #. Radiation appertization- use of gamma radiations to extend shelf life or sterilize meat, sea foods, fruits & vegetables. This process kills microbes in moist foods by producing peroxides from water, peroxides oxidizes cellular constituents.

8. ADDITION OF BACTERIOCINS:- This is addition of microbial product based inhibitors in food to control food borne pathogens. Bacteriocins are bactericidal proteins active against related species. Example- Nisin ; used in low acid foods to inactivate clostridium botulinum during canning process.

9. SALTING AND SUGARING:- Earliest cultures have used salt and sugar as preservative, it was common to store food in salt, sugar & honey.

#Pickling- In this method food is preserved in an edible “anti-microbial” liquid, typical pickling agents include brine (high in salt), vinegar, alcohol, vegetable oil, etc.

#CURING SALT- It is combination of & sodium nitrite with pink colour added to distinguish it from ordinary salt.

Sugar is used to preserve fruits, either in an anti-microbial syrup with fruit such as apples, pears, peaches, apricots, plums, or in crystallized form or in form of jam & jelly; where the preserved material is cooked in sugar. In crystallization it is cooked to the point of crystallization and the resultant product is then stored dry. In jellying fruit is cooked in sugar and then it solidifies to form gel.

10. FERMENTATION:- In some foods such as many cheeses, wines and beer specific microorganisms are used that combat spoilage from other less benign organisms.