Food Preservation

Various methods of food preservation techniques are described.

1. FPT311-Principles of Preservation EZHIL S GOWTHAMI M JAYABHARATHI N JOTHINANDHINI M KALAISELVI T

2. PRESERVATION Definition: The science that deals with the methods of prevention of decay or spoilage of food, allowing it to be stored in a fit condition for future use. Care should be taken during, Pretreatment, Cleaning of equipments, processing, cooling and storage.

3. Principles involved in preservation: 1. Prevention or delay of microbial decomposition (Asepsis, Filtration, low temperature, drying, anaerobic conditions, chemicals or antibiotics ) 2. Prevention or delay of self-decomposition of the food (Blanching, Prevention of oxidation by means of an antioxidant) 3. Prevention of damage by insects, animals, mechanical causes, etc . (Preserve food soon after preparation, without allowing it to stand for a longtime.)

4. ASEPSIS Asepsis means preventing the entry of microorganisms Maintaining of general cleanliness while, picking, grading, packing and transporting of fruits and vegetables. Washing or wiping of the fruits and vegetables before processing should be strictly followed .

5. PRESERVATION BY HIGH TEMPERATURE Coagulation of proteins, inactivation of enzymes by heat – destruction of microorganisms in food. Specific treatment varies with:

6. Pectic enzymes cause changes in flavour , clots particles in fruits- destroyed by heat at 85°C for 4 min/ 88°C for 1min. Juices, RTS and nectar- 85°C for 25-30 mins .

7. Bottle or Holding pasteurization- juices filled in bottles and pasteurized. Overflow method- juice heated to 2.5°C higher than pasteurization temperature. During filling and sealing temperature should not fall below pasteurization temperature. (Grape juice). Flash pasteurization- Juice heated to 5.5°C higher than pasteurization temperature and held for a minute . (Orange juices)

8. STERILIZATION Destruction of all viable microorganisms. Fruits and tomato products- 100°C for 30 min. Green pea, okra, beans – 116°C for 30-90 min. Empty can and bottles – boiling water for 30 min. UHT temperature – 149°C for 1-2 sec. Hot pack/ Hot fill: Filling of previously pasteurized or sterilized food, while still hot. Commercialized in 1950 S

9. Aseptic canning: Food is sterilized outside the can and then aseptically placed in previously sterilized cans which are subsequently sealed in an aseptic environment. Short time- high temp process. Four Operations ( i ) sterilization of product by appropriate quick heating, holding and cooling (ii) sterilization of containers and covers with superheated steam iii)aseptic filling of cooled, sterile product into sterile containers (iv) aseptic sealing of the containers with sterile covers .

10. PRESERVATION BY LOW TEMPERATURE Microbial growth and enzyme reactions are retarded in foods stored at low temperatures. There are three types, cellar storage refrigeration or chilling freezing CELLAR STORAGE (about 15*) The temperature in cellars (under ground rooms) where surplus food is stored in many villages is usually not much below that of the outside air and is seldom lower than 15*c. Root crops, potatoes, onions, apples can be stored for limited periods during winter season.

11. REFRIGERATION OR CHILLING(0-5*C ) Chilling temperature are obtained by ice or mechanical refrigeration. Preserved for a few days to many weeks. Commercial cold storages with proper ventilation and automatic control of temperature are now used. This used for semi perishable foods such as potatoes, apple. FREEZING(-18 TO -40*C) Microbial growth is inhibited and rate of chemical reactions is slowed down at low temperature. At temperatures below the freezing point of water, growth of microorganisms and enzyme activity are reduced to minimum. Quick frozen in about 90minutes or less. Placing them in contact with coil through which the refrigerant flows, blast freezing in which cold air is blown across the food and dipping in liquid nitrogen. Juices are frozen at -12 to -17*c .

12. PRESERVATION BY DRYING Microorganisms need moisture to grow so when the concentration of water in the food is brought down below a certain level, they are unable to grow. Moisture can be removed by either sun drying or mechanical drying. This is more rapid process as artificial heat under controlled conditions of temperature , humidity and air flow is provided by fruits and vegetables. In this method, juices are preserved in the form of powder.

13. PRESERVATION BY CHEMICALS Microbial spoilage is controlled by using chemical preservatives which do not include salt, sugar, acetic acid, oils, alcohols. But only microbial antagonists. The inhibitory action of preservatives is due to mechanism of cell division, permeability of cell membrane and activity of enzymes. Pasteurized squashes, cordials and crushes have cooked flavour . After the container is opened, they ferment and spoil within a short period, particularly tropical climate. To avoid this we use chemical preservatives. Two important chemical preservatives are permitted, sulphur dioxide (including sulphites ) benzoic acid ( include benzoates) These are allowed in India according to Fruit Product Order of 1955.

14. SULPHUR DIOXIDE It is used for preservation of juice, pulp, nectar, squash, cordial. It against action of bacteria, moulds and inhibit enzymes. It act as antioxidant. It helps to retention of ascorbic acid, carotene and other oxidizable compounds. It is better compare to sodium benzoate. PH Saccharomyces ellipsoideus (yeast) Mucor (mould) Penicillium (mould) Mixed bacteria 2.5 200ppm 200ppm 300ppm 100ppm 3.5 800ppm 600ppm 600ppm 300ppm 7.0 Above 5000ppm Above 5000ppm Above 5000ppm aboveppm

15. BENZOIC ACID Benzoic acid is more effective against yeast than mold. Juices having a PH of 3.5 to 4.0 –add 0.06 to 0.10% of sodium benzoate. Less acid – add 0.3% of sodium benzoate

16. PRESERVATION BY FILTRATION The juices are clarified by settling or by using ordinary filters, and then passed through special filters which are capable of retaining yeasts and bacteria. Various types of germ-proof filters are used for this purpose It is not used in India This method is used for soft drinks, fruit juices and wines in USA, Germany and etc recently

17. PRESERVATION BY CARBONATION Carbonation is the process of dissolving sufficient carbon dioxide in water or beverage so that the product when served gives off the gas as fine bubbles and has a characteristic taste. Fruit juice beverages - 1 to 8 g per liter. Another advantage of carbonation is the removal of air thus creating 'an anaerobic condition, which reduces the oxidation of ascorbic acid and prevents browning. High carbonation should, however, be avoided as it usually destroys the flavor of the juice. The keeping quality of carbonated fruit beverages is enhanced by adding about 0.005 per cent sodium benzoate.

18. Syrups containing 66 per cent or more of sugar do not ferment. Sugar absorbs most of the available water . Thus sugar acts as a preservative by osmosis Fruit syrup, jam, jelly, marmalade, preserve, candy, crystallized fruit and glazed fruit are preserved by sugar. PRESERVATION BY SUGAR

19. PRESERVATION BY FERMENTATION FERMENTATION Decompositions of carbs by enzyme / microorganism PRESERVATION BY FERMENTATION One of the oldest method Foods preserved by alcohol / organic acid formed by microbial organism Keeping quality of alcoholic beverages, vinegar & fermented pickles depends upon presence of alcohol, AA & LA respectively. While sealing care should be taken to avoid secondary fermentation. 14% alcohol – preservative in wine EXAMPLE: wines, beers, vinegar, fermented drinks, fermented pickles.

20. PRESERVATION BY SALT @ conc 15-25% Inhibits enzymatic browning & discolouration Act as anti oxidant Form of brine used in canning & pickling SALT ACTION Causing high osmotic pressure Dehydrating foods & microorganisms Ionizing to yield chloride ion Reducing the solubility of O2 in water, sensitizing the cells against co2, & interfering with the action of proteolytic action

21. PRESERVATION BY ACID Low acid foods spoilt rapidly High acid foods inhibit growth of spoilage organism Acidic additives- vinegar / citric acid lowers the protein level Action on carbs produce LA In certain cases, nutrient level increases, through vitamin & protein synthesis AA(lime), CA(lime) & LA. 2% prevents spoilage of products Vinegar+salt – for onion Vinegar – pickles, chutney, sauces, ketchups. CA – squashes, jam & jelly

22. Preservation by oil and spices Layer on surface of any food produces – Anaerobic conditions Prevent growth of mould and yeasts Eg : Pickles . Enough oil added – to preserve for long time Spices- Tumeric , pepper , asafoetida – for bacteriostatis effect Oil provide airtight seal for ingredients-improve shelf life

23. Pickles

24. Preservation by Antibiotics Metabolic products of microorganisms Germicidal effect called antibiotics Not only for medical use also used for preserving.

25. Nisin streptococcus lactic Organism found in milk and fermented dairy products Non toxic , no effect on sensory quality Preserving acid foods – more stable canning mushroom , tomatoes , milk products Suppresses gas production , spore forming bacteria , toxin producing clostridium botulinum

26. Subtilin : Obtained from bacilus subtilis Preservation of asparagus , corn and peas. Reduce thermal process requirement . Primaricin : Antifungal antibiotic Treating fruits and vegetables

27. Preservation by Irradiation Gamma rays / electron beams Passes through foods Collision between ionizing radiation at atomic and molecules level Radiation dose must be carefully controlled Amount and time of validation also be controlled Dose of 1 Mrad – not hazardous

28. Irradition dosage Dose of 10³ to 10^7 rad kills micro organisms 10^3 to 10^6 rad - kills insects 10^2 to 10^3rad - lethal to humans 10^3 to 10^4 rad - sprouting of potatoes,onions,carrots are inhibited. For bacterial endospores 3*10^6 rad - sterilize To 5*10^4 rad – yeast and fungi

29. SOURCES OF IRRADIATIONO GAMMA RAYS:  cobalt (Cobalt 60) Cesium 137 X-RAYS: produced by reflecting a high-energy stream of electrons off a target substance into food. 

30. ACCELERATED ELECTRONS Stream of high energy electrons Electron accelerator Low in radioactivity Shorter exposure

31. RADURA SYMBOL

32. ADVANTAGES Increased shelf life Reduce the use of chemical preservatives Reduce the risk of food born disease. No /less heat is enough

33. LIMITATIONS Not applicable for all foods. Peach Nectarines Dairy products cannot be irradiated Chemicals with nutritional and flavor functions can be affected.

34. QUESTIONS Juices frozen temperature at -----------*c Chemical preservatives are include benzoic acid, acetic acid, alcohol.(T/F). Sulfur dioxide are helps to retention of ---------- compounds. Temperature required to destroy E.coli -------- Flah preservation is suitable for ---------- Sterilization temperature for fruit and tomato products ------ Decomposition of carbohydrates by enzyme / microorganism is called________ _________act as an anti oxidant while preserve the foods. The required amount of acid to preserve foods_______ Commonly used antibiotic in food preservation________