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Food preservation by sajib reza
Food preservation involves techniques to prevent food from spoiling, such as canning, drying, refrigeration, freezing, smoking, and adding chemical preservatives. The main goals of food preservation are to prevent the growth of microorganisms and slow the oxidation of fats. This allows food to be stored for future use while maintaining quality, edibility, and nutritive value. Various preservation methods work by inhibiting microbial growth through processes like preventing bacterial access, removing microbes, or killing them through techniques like heating, freezing, or irradiation. Proper preservation ensures food remains safe from contamination or loss of qualities like texture and flavor during storage.
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Food preservation by sajib reza
- 1. Food preservation Md .Sajib Al Reza Lecturer Nutrition And Dietetics College Of Nursing Science Dinajpur Dinajpur, Bangladesh Email: [email protected]
- 2. Food preservation… … •Food Preservation: The term food preservation refers to any one of a number of techniques used to prevent food from spoiling. It includes methods such as canning, pickling, drying and freeze- drying, irradiation, pasteurization , sterilization, curing, pickling, irradiation, chilling, refrigeration, dehydration, smoking, and the addition of chemical additives. • Food preservation is to prevent the growth of microorganisms as well as slowing the oxidation of fats that cause rancidity. • Food preservation is known “as the science which deals with the process of prevention of decay or spoilage of food thus allowing it to be stored in a fit condition for future use”. Preservation ensures that the quality, edibility and the nutritive value of the food remains intact.
- 3. Continue …. …. Preservationinvolves – preventing the growth of bacteria, fungi and other microorganisms, as well as retarding oxidation of fats to reduce rancidity. Basically food preservation ensures that food remains in a state where it is • not contaminated by pathogenic organisms or chemicals • does not lose optimum qualities of colour, texture, flavor and nutritive value • Stop oxidation that causes the destruction of essential biochemical compounds and/or the destruction of plant and animal cells. The various food preserving methods are all designed to reduce or eliminate one or the other (or both) of these causative agents.
- 4. Principles of foodpreservation … … Principles of food preservation: (A) Prevention or delay of the growth of micro-organisms (i) Avoiding invasion of micro-organisms e.g. by aseptic techniques (ii) Removing micro-organisms e.g. filtration (iii) Inhibiting the growth and activity of micro-organisms e.g. freezing, refrigeration, drying, anaerobic conditions, chemicals or antibiotics (iv) Killing the micro-organisms e.g. heat or irradiation (B) Prevention or delay of self-decomposition (i) Destruction or inactivation of inherent enzymes naturally existing in food e.g. by blanching (ii) Prevention or delay of chemical reactions e.g. prevention of oxidation by using antioxidants
- 5. Continue …. …. (C)Prevention of damage from insects or animals (i) By using suitable chemicals to kill insects or animals from destroying the foods. (ii) By storing foods in dry, air tight containers to prevent the insects or animals from destroying them.
- 6. Various methods offood preservation … …
- 7. Continue …. …. •Drying: Food drying is a method of food preservation in which food is dried (dehydrated or desiccated) under sunshine or open air through the removal of water to inhibits the growth of bacteria, yeasts, and mold. Meats, fish, fruits, and vegetables, chilies, mangos are preserved by sun drying from ancient time. • Dehydration: Dehydration, usually describes the removal of moisture by applying artificial heat current under controlled conditions. Dehydration Drying A faster process A slower process Under controlled hygienic conditions Under open-air conditions with little hygienic control Not dependent on the weather Not possible in cloudy weather or rainy days Investment on machinery and processing cost is needed No machinery and processing cost is needed
- 8. Continue …. …. •Cooking: Cooking or cookery is the art, technology and craft of preparing food for consumption with or without the use of heat. Cooking methods include Roasting, Baking, Boiling, Frying, Steaming, Smoking etc. • Cellar storage: The temperature in cellar (underground rooms) is seldom lower than 15oC. It is not enough to prevent the action of many spoilage organisms or of plant enzymes. Root crops, potatoes, cabbage, apples, onions and similar foods can be stored for limited periods. • Refrigeration (or) chilling (0 to 5oC): Refrigeration at 5oC lowers the growth rate of micro-organisms but does not stop microbial growth. Chilling temperature are obtained and maintained by means of ice or mechanical refrigeration. It may be used temporary preservation until some other preservative process is applied. Most perishable foods, including eggs, dairy products, meats, sea foods, vegetables and fruits, may be held in chilling storage for a limited time.
- 9. Continue …. …. •Freezing: For frozen food, it should be stored at or below -18 oC where the enzymatic and microbial changes may be stopped or extremely slow. Frozen food (- 10 oC) usually does not have any free water (reduce Aw). Freezing may kill some but not all microorganisms and slowing of oxidation reactions. Food should not be refrozen after thawing. • Smoking: Smoking is the process of flavoring, browning, cooking, or preserving food by exposing it to smoke from burning or smoldering material, most often wood. Meats and fish are the most common smoked foods. In cold smoking cold smoking are typically done between 20 to 30 °C. Cold smoking does not cook foods and foods take on a smoked flavor, but remain relatively moist. Hot smoking occurs within the range of 52 to 80 °C. Within this temperature range, foods are fully cooked, moist, and flavorful. Smoke roasting or "smoke baking" refers to any process that has the attributes of smoking combined with either roasting or baking above 82 °C.
- 10. Continue …. …. •Salting: Salting is the preservation of food with dry edible salt. It is related to pickling, brining, and is one form of curing. Reduction in water activity sufficient to delay or prevent microbial growth. salt solution (20-40%/100ml water) known as brine. Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated. salt-cured foods are salted fish, salt-cured meat, hams, bacon, Vegetables such as runner beans, cucumbers and cabbage are preserved in this method. • Pickling: Pickling is the process of preserving food by anaerobic fermentation in brine or vinegar. The resulting food is called a pickle. 20% Vinegar or citric acid lower the pH of 4.6 or lower and thus inhibit the growth of many micro-organisms. Pickling can preserve perishable foods for months. Antimicrobial herbs and spices, such as mustard seed, garlic, cinnamon or cloves, are often added. Foods that are pickled include meats, fruits, eggs, and vegetables, jams, jellies and squashes, pickles, sauces and chutney.
- 11. Continue …. …. •Jugging: Meat can be preserved by jugging. Jugging is the process of stewing the meat (commonly game or fish) in a covered earthenware jug or casserole. The animal to be jugged is usually cut into pieces, placed into a tightly-sealed jug with brine or gravy, and stewed. Red wine and/or the animal's own blood is sometimes added to the cooking liquid. • Sugar solution: Sugar binds moisture and thus can preserve food by preventing the growth of microorganisms if a high concentration (65% or above) is used. Sugar tends to draw water from the microbes (plasmolysis). This process leaves the microbial cells dehydrated, thus killing them. Products such as apples, pears, peaches, apricots, and plums, jams and jellies are preserved by using sugar. Heating the fruit with antimicrobial sugar syrup.
- 12. Continue …. …. •Chemical: An ideal preservative should meet the following criteria: • (i) can inhibit the growth of a wide range of micro-organisms • (ii) should be non-toxic to humans • (iii) should not be expensive • (iv) should not affect the flavour, taste or aroma of the food product • (v) should not be inactivated by the food itself • (vi) should not promote the development of resistant micro-organisms • (vii) should kill rather than inhibit the micro-organisms • Preservative food additives can be antimicrobial—which inhibit the growth of bacteria or fungi, including mold—or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food constituents. Some familiar examples of food additives are sodium benzoate and benzoic acid; calcium, sodium propionate, and propionic acid; calcium, potassium, sodium sorbate, and sorbic acid; and sodium and potassium sulfite. Examples of the latter class of additives include calcium, sodium ascorbate, and ascorbic acid (vitamin C); butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT); lecithin; and sodium and potassium sulfite and sulfur dioxide.
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- 14. Continue …. …. •Irradiation: Food absorbs and is heated up by radiant energies. Radiant energies can kill microorganisms without marked increase of temperature as well as marked changes in the nature of food. Gamma rays, x-rays and electromagnetic, ultra-violet radiations are commonly used for food preservation. Irradiation can be used in a wide range of area in food preservation: • (i) Poultry products and seafood • (ii) Fruits • (iii) Prevention of sprouting in potatoes and onions • (iv) Delaying ripening in fruits • (v) Preservation of seafood • (vi) Prevention of insect infestation in dry foods and food products • Lye: Sodium hydroxide (lye) makes food too alkaline for bacterial growth. Lye will saponify fats in the food, which will change its flavor and texture. Ex: Olive recipes
- 15. Continue …. …. •Vacuum packing: Vacuum packing is a method of packaging that removes air from the package prior to sealing. This method involves (manually or automatically) placing items in a plastic film package, removing air from inside, and sealing the package. Vacuum packing reduces atmospheric oxygen, limiting the growth of aerobic bacteria or fungi. It is used to store cereals, nuts, cured meats, cheese, smoked fish, coffee, and potato chips. • Anaerobic condition/ Modified atmosphere: Anaerobic condition means a condition lack of or containing only minimum amount of air or oxygen. It can prevent the surviving bacteria in food from growing in the container. The container is completely filled with food and air in unfilled space is removed or replaced by nitrogen or carbon dioxide. • Canning: Canning involves cooking food, sealing it in sterilized cans or jars, and boiling the containers to kill or weaken any remaining bacteria and their spores as well as inactivating enzymes as a form of sterilization in which over 100 C is used. The packaging materials for canning can be tin or glass. The basic principle behind canning is that a food is sterilized, usually by heating, and then placed within an air-tight container. Example: meat, fruit, vegetables, and even milk.
- 16. Continue …. …. Pasteurisation(temperature below 100 C): Pasteurisation is a heat treatment that kills part of the micro-organisms present in food using a temperature under 100 C. The temperature used ranges from 65-75 C. There are two ways of pasteurisation: ❖ HTST (High temperature-short time) • Food product is heated at high temperature for a short time. For example, milk is heated to 72 C and held for 15 seconds. ❖ LTLH (Low temperature-long time) • Food product is heated at a lower temperature for longer period of time. For example, milk is heated to 62.8 C and held for 30 minutes. Boiling or heating at about 100 C: Most fruits and vegetables can be preserved for a longer time by applying heat at about 100 C. Inherent enzymes which initiate self-decomposition can be destroyed after boiling at 100 C. This process is called blanching. Sterilization (temperature 100 C or above): It is a process that all micro-organisms are being killed at high temperature or radiation. The time and temperature necessary for sterilization vary with the type of food.
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- 18. Continue …. …. •Fermentation: Fermentation in food processing is the process of converting carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic conditions. Fermentation usually implies that the action of microorganisms is desired. similar processes take place in the leavening of bread (CO2 produced by yeast activity), and in the preservation of sour foods with the production of lactic acid, such as in sauerkraut and yogurt. Example: wine, beer, and cider, cheese, vinegar, olives. • Hurdle technology: Hurdle technology is a method of ensuring that pathogens in food products can be eliminated or controlled by combining more than one approach. These approaches can be thought of as "hurdles" the pathogen has to overcome if it is to remain active in the food. The right combination of hurdles can ensure all pathogens are eliminated or rendered harmless in the final product.
- 19. Continue …. …. •Baking: Baking is a method of cooking food that uses prolonged dry heat, normally in an oven, but also in hot ashes, or on hot stones. Heat is gradually transferred "from the surface of cakes, cookies, and breads to their centre. Bread, cakes, pastries, puddings, vegetables and potatoes may be cooked by this method. • Blancing: Food is dipped in boiling water for 5seconds to 2 minutes. blanching involves pouring enough boiling water on the food to immerse for sometime in boiling temperature, than immediately immerse in cold water. It inactivate and destroy enzyme. It improves color and flavor of food.
- 20. Importance of FoodPreservation …. …. Food preservation helps in: 1. Increasing the self-life of foods thus increasing the supply. So many perishable foods can be preserved for a long time. 2. Making the seasonal food available throughout the year. 3. Adding variety to the diet. 4. Saving time by reducing preparation time and energy, as the food has already been partially processed. 5. Stabilising prices of food, as there is less scope of shortage of supply to demand. 6. Decreasing wastage of food by preventing decay or spoilage of food. 7. Improving the nutrition of the population. Preserved foods help people to bring a variety in the diet, thereby decreasing nutritional inadequacies.
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