FOOD PRESERVATION BY HEAT TREATMENTS.pptx

Food preservation using heat treatment methods. Brief introduction of methods such as blanching, canning, frying, sterilization and pasteurization

1. FOOD PRESERVATION BY HEAT TREATMENTS

2. FOOD PRESERVATION Food Preservation is the process of treating and handling food in such a way that it : ❏ Maintains the nutritional value, texture and flavor of the food. ❏ Prevents food and vegetables from getting spoiled. ❏ Increases the shelf life of the food product. ❏ Decreases food wastage. ❏ Makes food available throughout the year.

3. PRINCIPLES OF FOOD PRESERVATION Prevention or delay of microbial decomposition ❏ By keeping out microorganisms (asepsis). ❏ By removal of microorganisms. ❏ By hindering the growth and activity of microorganisms (eg. by low temperatures, drying, anaerobic conditions, or chemicals). ❏ By killing the microorganisms (by heat or radiation). Prevention or delay of self decomposition of the food. ❏ By destruction or inactivation of food enzymes ( by blanching). ❏ By prevention or delay of chemical reactions (by using antioxidant). Protection against insects, rodents, and animal infestation

4. THERMAL PROCESSES Thermal processing is defined as the combination of temperature and time required to eliminate a desired number of microorganisms from a food product. "Thermal" refers to processes involving heat Heating food is an effective way of preserving. The basic purpose for the thermal processing of foods is, ❏ Reduces or destroy microbial activity. ❏ Reduces or destroy enzyme activity. ❏ Makes the food meet a certain quality standard.

5. TYPES OF THERMAL PROCESSING ❏ BLANCHING (at about 100o C) ❏ PASTEURIZATION (below 100o C) ❏ STERILIZATION (above 100o C) ❏ CANNING MILD PROCESSES - BLANCHING AND STERILIZATION SEVER E PROCESSES - CANNING, BAKING, ROASTING, FRYING

6. MILD HEAT TREATMENT SEVERE HEAT TREATMENT ❏ Kills pathogens and inactivates enzymes. ❏ Ad vantag e - Minima l damage to flavour, texture and nutritional quality. ❏ Disad v antag e - Sho r t shelf life. ❏ Example s - P asteurization, Blanching ❏ Kills all bacteria. ❏ Ad v antag e - Lon g shel f li f e ❏ Disad v antag e - Major changes in texture, flavor and quality. ❏ Example s - Canning

7. STERILIZATION ❏ A controlled heating process used to completely eliminate all living microorganisms, including thermoresistant spores in milk or other food. ❏ It can be achieved by moist heat, dry heat, filtration, irradiation, or by chemical methods. ❏ Used to treat all types of food products such as milk, juices, beer and many others. ❏ Various time/temperature combinations are applied, depending on the product properties and shelf-life requirements.

8. Sterilization with moist heat: Temperatures generally range from 110 to 130°C with sterilization times being from 20 - 40 min. Sterilization with dry heat: For killing bacterial endospores by dry heat, longer exposure times (e.g. up to 2 hours) and higher temperatures (e.g. 160 – 180°C) are required than with moist heat. Sterilization by chemical means: Chemical means may also be applied. Ethylene oxide is used to sterilize food, plastics, glassware, and other equipment.

9. PASTEURIZATION ❏ Temperature applied is below 100o C. ❏ The heating may be by means of steam, dry heat or electric currents and the products are cooled promptly after the heat treatments. ❏ It can be used to destroy relatively heat sensitive microorganisms. (Named after Louis Pasteur) ❏ Pasteurization is a process of heat processing a liquids or a food to kill pathogenic bacteria to make the food safe to eat. This process is named after Louis Pasteur.

10. TYPES OF PASTEURIZATION Low Temperature Low Time (LTLT) L T L T i s heatin g foo d t o a low temperature for a long time -62.8°C for 30 minute Also called the Holding/ Batc h method. Ultra HIgh Temperature ( UHT) Ultra-high-temperature (UHT) pasteurization involves heating milk or cream to 138° to 150° C (280° to 302° F) for one or two seconds. Packaged in sterile, sealed containers, UHT milk may be stored without refrigeration for months. High Temperature Short Time (HTST) HTST is heating food to a high temp and maintain for a sho r t time: -71.7°C for 15 second Also called the Continuous/ Flas h method.

11. Effect s of Pasteurization Positive effects of pasteurization : Destruction of pathogenic microorganisms. Increases the safety of market milk for human consumption. Improves keeping quality an d inactivatio n of certain naturally occurring enzymes. The negative effects of pasteurization: It also destroys the beneficial bacteria and other essential nutritions. There is small loss of native aroma particularly in case of fruit juices.

12. PASTEURIZATION STERILIZATION Partial destruction of microorganism. Temperature below 100oC. Minimum damage to flavor, nutritional quality and texture. Short shelf life. Another preservation method has to be used such as refrigeration/ freezing. Complete destruction of microorganism. Temperature 100o C and above. Major changes in flavor, nutritional quality and texture. Long shelf life. No other method required.

13. CANNING ❏ Preservation of food in sealed containers followed by application of heat treatment. ❏ Prevents microbial contamination and inactivates degradative enzymes. ❏ Oxidation may occur in food resulting in change in color and flavour of food and also reducing the nutrient content. ❏ Is done in tin cans, glass containers, aluminium and plastic pouches ❏ Done at high temperature and high p r essu r e . 11 6 - 12 1 ’

14. FOODS THAT ARE CANNED Low Acid Foods - Meat, fish, poultry, dairy, which fall into a pH range of 5 to 6.8. These foods don’t have enough acid to stop bacteria from forming. Acid Foods - pH range between 3.7 and 4.5. Fruits such as pear, oranges, tomatoes fall in this class. These foods have enough acid within themselves naturally, they don’t require a higher temperature to kill bacteria. High Acid Foods - pH value range from 2.3 to 3.7. (Pickled products and fermented foods, also jams, and jellies.)

15. TYPES OF CANNING Water-Bath Canning ❏ Als o referred a s hot water canning.Boiling water bath. ❏ Use s a la r ge kettle of boiling wate r . ❏ Filled jars are submerged in the water and heated to an internal temperature of 212°F for a specific period of time. ❏ This method is used for processing high-acid foods, suc h a s fruit, items made from fruit, pickles, pickled food, and tomatoes. Pressure Canning ❏ Pressure canning uses a large kettle that produces steam in a locked compartment ❏ The filled jars in the kettle reach an interna l temperatur e of -240 °C under a specific pressure that is measure d wit h a dial gauge or weighte d gauge on the pressure-canner cover. ❏ A pressure canner should be used for processing vegetables and other low-aci d foods, suc h a s meat, poultry and fish.

16. BLANCHING Blanching is a slight heat treatment, using hot water or steam applied mostly to vegetables. Time duration of 30-60 seconds. Retains color, texture, flavor, and nutritional content of fruits and vegetables. Keeps the outer surface soft and gives the inner surface a little crisp. Stops the enzymatic reactions that take place within the fruits and vegetables and help to preserve them for a longer time. Complete immersion of fruits and vegetables is done within high simmering water for a few minutes and then placed in an ice bath to instantly cool them. There are three major steps in the blanching process. Preheating Blanching Cooling

17. REFERENCES ❏ ANON. 1982. Canned Foods: Principles of Thermal Process Control, Acidification and Container Closure Evaluation. 4th ed. The Food Processors Institute, Washington, D.C. ❏ BALL, C. O. and OLSON, F. C. W. 1975. Sterilization in Food Technology. McGraw-Hill, New York. ❏ DESROSIER, N. W. and DESROSIER, J. N. 1977. Technology of Food Preservation. 4th ed. AVI Publishing Co., Westport, Conn. ❏ LOPEZ, A. 1981. A Complete Course in Canning. 11th ed. Books 1 and 2. The Canning Trade, Baltimore. ❏ Potter N.N. (1986) Heat Preservation and Processing. In: Food Science. Springer, Dordrecht. ❏ Kanemitsu et al. (May 2005). "A comparative study of ethylene oxide gas, hydrogen peroxide gas plasma, and low-temperature steam formaldehyde sterilization". ❏ Molins RA (2001). Food irradiation: principles and applications . ❏ M.N. Ramesh,2003. Encyclopedia of Food Sciences and Nutrition (Second Edition).

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