FOOD PRESERVATION ppt.pptx

Food preservation includes food processing practices which prevent the growth of microorganisms, such as yeasts (although some methods work by introducing benign bacteria or fungi to the food), and slow the oxidation of fats that cause rancidity. Food preservation may also include processes that inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut during food preparation. By preserving food, food waste can be reduced, which is an important way to decrease production costs and increase the efficiency of food systems, improve food security and nutrition and contribute towards environmental sustainability.For instance, it can reduce the environmental impact of food production.
Many processes designed to preserve food involve more than one food preservation method. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit's moisture content and to kill bacteria, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination).
Different food preservation methods have different impacts on the quality of the food and food systems. Some traditional methods of preserving food have been shown to have a lower energy input and carbon footprint compared to modern methods.

1. FOOD PRESERVATION Name – Vedant Sawant Roll no.-19FET107 Food microbiology presentation

2. Food preservation Food preservation is the process of treating and handling food to stop or greatly slow down spoilage ( loss of quality,edibility or nutritive value ) caused or accelerated by microorganisms. Food preservation may also include processes that inhibit visual deterioration, such as the  enzymatic browning . Different food preservation methods have different impacts on the quality of the food and food systems. Eg -Some traditional methods of preserving food have been shown to have a lower  energy input  and  carbon footprint  compared to modern methods.

3. History

4. Food spoilage

5. Why to preserve food ? To add variety to our meals during seasons when the food items are unavailable. Perishable foods have been made available year-round . To make food item available in areas where it is not grown. Makes transportation of food items easier. Reduces food wastage. To preserve colour ,taste and nutritive value of food. Also, foods in general are being produced in a cleaner and more sanitary manner than before.

6. Principles of food preservation 1. Prevention or delay of microbial decomposition a By keeping out microorganisms (asepsis) b By removal of microorganisms, e.g., by filtration c By hindering the growth and activity of microorganisms, e.g., by low temperatures, drying, anaerobic conditions, or chemicals d By killing the microorganisms, e.g., by heat or radiation 2. Prevention or delay of self-decomposition of the food a By destruction or inactivation of food enzymes, e.g., by blanching b By prevention or delay of purely chemical reactions, e.g., prevention of oxidation by means of an antioxidant 3. Prevention of damage because of insects, animals, mechanical causes, etc.

7. Preservation methods classification Traditional methods Drying Cooling Free z ing Boiling Heating Salting & Sugaring Pickling Lye Canning Jellying Smoking Industrial modern methods Pasteuri z ation Vaccum packing Artificial food additives Irradiation Pulsed electric field electroporation Modified atmosphere Non-thermal plasma High pressure food preservation Hurdle technology Biopreservation

8. Food preservation methods The chief methods of food preservation are as follows: 1. Asepsis, or keeping out microorganisms. 2. Removal of microorganisms. 3. Maintenance of anaerobic conditions, e,g ., in a sealed, evacuated container. 4. Use of high temperatures. 5. Use of low temperatures. 6. Drying; this includes the tying up of water by solutes, hydrophilic colloids, etc . 7. Use of chemical preservatives, either developed by microorganisms or added. 8. Irradiation.

9. 9. Mechanical destruction of microorganisms, e.g., by grinding, high pressures, etc. (not used industrially). 10. Combinations of two or more of above methods. Only rarely is a single method effective, and usually several are combined. When preservative methods are combined, the required intensity of each method usually is reduced to less than that for preservation by one method alone. For eg - When benzoate or sórbate is added to fruit juices, less heat is required for sterilization of these products . Foods previously irradiated with gamma rays or treated with antibiotic tylosin require less heat for their sterilization than foods not so treated.

10. Asepsis Natural protection -outer layer of animal and plant tissue protects the inner layer free from microorganisms. This protective covering will delay/prevent microbial decomposition eg . Shells of nuts, skin of fruits and vegetables,etc . Packaging of foods - such as wrapping, hermetically sealed containers. This methods will prevent primarily contamination during handling. Sanitary methods of handling and processing foods- eg . In dairy industry, contamination with microorganisms is avoided as much as possible in the production and handling of market milk. Removal of microorganisms Filtration Centrifugation/Sedimentation Washing Trimming  

11. Anaerobic conditions A preservative factor in sealed, packaged foods may be the anaerobic conditions in the container. A complete fill , evacuation of the unfilled space (the head space in a can), or replacement of the air by carbon dioxide or by an inert gas such as nitrogen will bring about anaerobic conditions. Spores of some of the aerobic sporeformers are especially resistant to heat and may survive in canned food but be unable to germinate or grow in the absence of oxygen. Production of carbon dioxide during fermentation and accumulation at the surface will serve to make conditions anaerobic there and prevent the growth of aerobes.

12. Preservation using high temperatures Pasteurization Pasteurization is a heat treatment that kills part but not all of the microorganisms present and usually involves the application of temperatures below 100 C. The heating may be by means of steam, hot water, dry heat, or electric currents, and the products are cooled promptly after the heat treatment. Pasteurization is used when more rigorous heat treatments might harm the quality of the product, as with market milk, when one aim is to kill pathogens, as with market milk, when the main spoilage organisms are not very heat resistant, such as the yeasts in fruit juices, when any surviving spoilage organisms will be taken care of by additional preservative methods to be employed, as in the chilling of market milk, when competing organisms are to be killed, allowing a desired fermentation, usually by added starter organisms, as in cheese making.

13. Heating at about 100 C Formerly, home canners processed all foods for varying lengths of time at 100 C or less. Now, most home canners use pressure cookers for the less acid foods. Methods- Baking Simmering Roasting Frying Cooking Warming up 3. Heating above 100 C Temperatures above 100 C usually are obtained by means of steam under pressure in steam pressure sterilizers or retorts. Thus with no pressure the temperature at sea level is 100 C; with 5 lb of pressure, 109 C; with 10 lb, 115.5 C; and with 15 lb, 121.5 C. When liquid foods are to be sterilized before their introduction into sterile cans, high steam pressures are used to apply a high temperature for a few seconds.

14. Canning Canning is defined as the preservation of foods in sealed containers and usually implies heat treatment as the principal factor in the prevention of spoilage. Spallanzani in 1765 preserved food by heating it in a sealed container Nicolas Appert “ father of canning ” gave exact directions for the preservation of a wide variety of foods in cork- stoppered , wide-mouthed glass bottles, which he heated for hours in boiling water. Appert’s original container, the cork- stoppered , wide-mouthed glass jar , was used in much of the early canning. Most modern cans are made of steel plate coated with tin. The trend is toward a thinner and more even coating of tin. Enamels are coated onto flat sheets of plate before the manufacture of cans to prevent or slow discoloration or corrosion.

15. Preservation using low temperatures Freezing ■ Sharp freezing usually refers to freezing in air with only natural air circulation or at best with electric fans. The temperature is usually −23.3 C or lower but may vary from −15 to −29 C , and freezing may take from 3 to 72 hr. ■ Quick freezing , in which the food is frozen in a relatively short time. Quick freezing is variously defined but in general implies a freezing time of 30 min or less and usually the freezing of small packages or units of food. ■ Quick freezing is accomplished by one of three general methods: – direct immersion of the food or the packaged food in a refrigerant – indirect contact with the refrigerant – air-blast freezing

16. Quick Freezing • small ice crystals formed • blocks or suppresses metabolism • brief exposure to concentration of adverse constituents • no adaptation to low temperatures • thermal shock (too brutal a transition) • no protective effect • avoid internal metabolic imbalance Slow Freezing • large ice crystals formed • breakdown of metabolic rapport • longer exposure to adverse or injurious factors • gradual adaptation • no shock effect • accumulation of concentrated solutes with beneficial effects 2. Chilling Storage is at temperatures not far above freezing and usually involves cooling by ice or by mechanical refrigeration. Enzymatic and microbial changes in the foods are not prevented but are slowed considerably. It may be used as the main preservative method for foods or for temporary preservation until some other preservative process is applied.

17. Preservation using drying Solar drying Solar drying is limited to climates with a hot sun and a dry atmosphere and to certain fruits, such as raisins, prunes, figs, apricots, nectarines, pears, and peaches. The fruits are spread out on trays and may be turned during drying. Fish, rice, and other grains may also be sun-dried. Freeze drying Sublimation of water from a frozen food by means of a vacuum plus heat applied at the drying shelf, is being used for a number of foods, including meats, poultry, seafood, fruits, and vegetables. Frozen thin layers of foods of low sugar content may be dried without vacuum by sublimation of moisture during passage of dry carrier gas.

18. Drying by Mechanical Dryers Most methods of artificial drying involve the passage of heated air with controlled relative humidity over the food to be dried or the passage of the food through such air. A number of devices are used for controlled air circulation and for the reuse of air in some processes. The simplest dryer is the evaporator or kiln, sometimes used in the farm home , where the natural draft from the rising of heated air brings about the drying of the food. An alternative method is to move the food on conveyor belts or on trays in carts through the heated air .

19. Smoking Most of the preservative effect of the smoking of foods is due to the drying of the food during the process. Drying is the main preservative factor, especially drying at the surface of the food. Smoking can be done in four ways: cold smoking, warm smoking, hot smoking, and through the employment of "liquid smoke". Other methods Electronic heating Foam-mat drying , in which liquid food is whipped to a foam, dried with warm air, and crushed to a powder. Tower drying in dehumidified air at 30 C or lower has been successful with tomato concentrate, milk, and potatoes.

20. Preservation using modified atmospheres MAP (Modified Atmosphere Packaging). ( MAP ) is a  packaging  system that involves changing the gaseous  atmosphere  surrounding a food product inside a pack, and employing  packaging  materials and formats with an appropriate level of gas barrier to maintain the changed  atmosphere  at an acceptable level for preservation of the food. Gas flush consists of an inert gas such as  nitrogen ,  carbon dioxide , or exotic gases such as  argon  or  helium  which is injected and frequently removed multiple times to eliminate  oxygen  from the package.  By decreasing or controlling the amount of oxygen present in a package, the food product remains fresher longer, extending its shelf life and ensuring it remains attractive to consumers.

21. 2. Vaccum packaging  Refers to the technique of removing air from a pack prior to sealing and it predates the use of gases as a means of food preservation. Its principal purpose is to remove oxygen by pulling the packaging material into intimate contact with the product. Hand and semi-automatically operated vacuum packaging chamber machines are available, offering a relatively low cost option (vs. MAP gas packaging). Main objective is to prevent  oxidation reactions  such as lipid oxidation, loss of certain vitamins, oxidative browning, loss of pigments, etc. 

22. Preservation using radiation UV Radiation Radiation with wavelengths near 260 nm is absorbed strongly by purines and pyrimidines and is therefore the most germicidal. Ultraviolet radiation around 200 nm is strongly absorbed by oxygen , may result in the production of ozone, and is ineffective against microorganisms. Source of UV radiation - quartz-mercury vapor lamps or low-pressure mercury lamps , which emit radiation at 254 nm. Factors Influencing Effectiveness- only direct rays are effective unless they come from special reflectors, and even then their effectiveness is reduced. Time Intensity Penetration

23. Ionizing Radiations X-rays - are penetrating electromagnetic waves which are produced by bombardment of a heavy-metal target with cathode rays within an evacuated tube. They are not currently considered economical for use in the food industry . Gamma rays- are like x-rays but are emitted from by-products of atomic fission or from imitations of such by-products. Cobalt 60 and cesium 137 have been used as sources of these rays in most experimental work thus far, with cobalt 60 being the most promising for commercial applications. Beta rays - are streams of electrons (beta particles) emitted from radioactive material. Electrons are small, negatively charged particles of uniform mass that form part of the atom. They are deflected by magnetic and electric fields. Their penetration depends on the speed with which they hit the target. The higher the charge of the electron, the deeper its penetration. 4. Cathode rays- are streams of electrons (beta particles) from the cathode of an evacuated tube. In practice, these electrons are accelerated by artificial means.

24. Microwave Microwaves are electromagnetic waves between infrared and radio waves. The energy or heat produced by microwaves as they pass through a food is a result of the extremely rapid oscillation of the food molecules in an attempt to align themselves with the electromagnetic field being produced. This rapid oscillation, or intermolecule friction, generates heat. The microwaves themselves do not result in any inactivation of foodborne microorganisms; rather, it is the heat produced by the excitation of food molecules that actually results in microbial destruction.

25. Preservation using food additives A food additive is a substance or mixture of substances , other than the basic food stuff, which is present in food as a result of any aspect of production, processing, storage or packaging. Those food additives which are specifically added to prevent the deterioration or decomposition of a food have been referred to as chemical preservatives . Factors that influence the effectiveness of chemical preservatives- (1)concentration of the chemical,(2)kind , number, age, and previous history of the organism (3) temperature (4) time and (5) the chemical and physical characteristics of the substrate in which the organism is found (moisture content, pH, kinds and amounts of solutes,etc ). Principal preservatives- Sodium Chloride, Sugar , Sulfur dioxide ,Nitrate and Nitrite, Sorbic Acid , Acetic Acid, Propionic acid ,Benzoic acid , Parabens , Epoxides , Antibiotics ,Diethyl pyrocabonate .

26. Groups Examples Preservatives Chemical preservatives Colors Natural, Synthetic Flavors Nature identical extracts Sweeteners Saccharin, Aspartame, Polyols Emulsifiers and Stabilizers Lecithin Antioxidants Vitamin E, BHA, BHT Flour improvers Vitamin C, Cysteine , Chlorine Humecants and Anticaking agents Polyhydroxy alcohols, Calcium silicate Leavening agents Baking soda, Ammonium carbonate Chelating agents Polycarboxylic acids Curing agents Sodium nitrite, Polyphosphates Nutrient supplements Thiamine, Nicotinic acid, Iron, Calcium Processing aids Acids, Acidity regulators, Gelling agents, Antifoaming agents

27. Other food preservation methods Pulsed electric fields non-thermal method of food preservation that uses short pulses of electricity for microbial inactivation and causes minimal detrimental effect on food quality attributes.   The process is based on pulsed electrical currents delivered to a product placed between two elctrodes . Mano -thermo- sonication a food preservation technology that efficiently combines the effects of pressure, heat and ultrasonic waves at an optimal level to reach the desired levels of food stability and safety while ensuring minimum negative effects on quality of food material. It is a developing technique proved for its antimicrobial action and enzyme inactivation preventing food spoilage without altering sensory properties of foods.

28. High pressure processing A “non thermal” food preservation technique that inactivates harmful pathogens and vegetative spoilage microorganisms using pressure. Also known as Pascalization ,  high hydrostatic pressure (HHP) processing, ultra high pressure (UHP) processing. 4. Aseptic packaging Also a type of thermal sterilization. It is process in which commercially sterilized food item is placed in a sterilized package followed by sealing under aseptic environment.  The process by which microorganisms are prevented from entering a package during and after  packaging . 

29. References Food microbiology by WC Frazier Modern Food Microbiology 6th edition - James M. Jay www.sciencedirect.com