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    Add as FriendPreservation of food by low temperature

    by: sweta

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    1 : ssseYour Text Here wf Preservation of foods by low temperatures By:-Sweta sahay Ms ramaiha college
    2 : Organisms at low temperatures cladosporium Cl. botulinum Penicillium Sporotrichum
    3 : monilia yeasts
    4 : Temperatures employed CELLAR STORAGE 5-15°C. For storing root crops,, potatoes, cabbage, celery, apples, etc. Growth of MO is slower. Humidity affects storage. COLD STORAGE OR CHILLING Mechanical refridgeration, For temporary storage For foods like- eggs, meats, sea food, vegs,fruits.
    5 : Cold storage foods
    6 : Cellar storage foods
    7 : Factors affecting spoilage Temperature Keeping cold foods cold means storing them at temperatures between 40°F, which is where normal refrigeration kicks in, down to about 0°F, which is where you'd want your freezer to be. Bacteria still multiply at cold temperatures, they just do it a lot more slowly. Lower the temp. greater the cost Optimal storage temp for certain foods Eg. Banana – to be stored at 13.3- 16.7°C Apples- undergo Low temp. Breakdown SWEET POTATOES KEEP BEST AT 12.8°C Temp of the fridge varies between 0-10°C
    8 : RELATIVE HUMIDITY RH varies with the food stored. Varies with the environmental factors. Too low rh yields loss of moisture, wilting, softening & damage. Too high rh results in condensation of water, growth of molds & mo. Changes in rh cause “sweating” of foods. Like all living organisms, bacteria need water to survive. Foods high in moisture like meats, poultry, seafoods and dairy products, as well as fruits and vegetables, are prime breeding ground for harmful bacteria. Low-moisture foods, including dried grains and legumes such as rice or beans, will typically keep for a very long time without spoiling or harboring bacteria.
    9 : Low temperature retards spoilage, but even subfreezing temperatures do not prevent multiplication of all microorganisms until about - 7°C is reached. Refrigerated foods are therefore subject to spoilage by moulds and by some yeasts and bacteria. Foods stored at -18°C remain free from microbial growth and a slow decrease in population may even occur. Foods and food products stored at room  temperature or in warm locations are easily spoiled by mesophilic arid thermophilic organisms.
    10 : Directions for storage Be sure to store products in the proper places. Items such as rice and pasta should be kept in cool, dry places. Frozen food should be kept at 0 degrees Fahrenheit or below, not 32 degrees. Refrigerated items should be stored at 41 degrees Fahrenheit or below. Potentially hazardous items-such as meat, egg and cheese products-can be kept safely refrigerated for up to seven days, according to the Food and Drug Administration (FDA). Freeze items such as meats if you might not be able to use them within seven days. • Check and record refrigerator temperatures at least twice a day. • Refrigeration units do not cool by cold temperatures alone. When placing foods in a refrigerator, allow sufficient space between packages for air circulation and keep items away from the inside walls. Do not store foods directly on the floor of a walk-in cooler.
    11 : Ventilation Control of air velocities in storage area Control of odors. Prevention of development of off odors. Rate of air circulation affects drying of foods.
    12 :
    13 : Air circulation in refridgerators
    14 : Composition of storage atmosphere In cold storage plants Controlled atmospheric gases Use of CO2, ozone & other gases for storage environment. Gas storage combined with chilling Optimal conc. Of CO2 or ozone has beneficial effects Food remains unspoiled for longer periods. Higher RH can be maintained without harm to the foods. Higher storage temperatures can be used without shortening the shelf life.
    15 : Other factors Combination of irradiation with chilling storage Use of UV RAYS in cold storage. Permits higher storage temperature Efficient for storing meat and cheese.
    16 : Frozen storage Frozen storage used for centuries. Today it is widely used method. Modern refridgerators equipped with frozen storage. Microbial growth is fully controlled. Action of food enzymes retarded. Frozen storage• Freezers keep food at 0°F or below.• Freezers are never intended to cool food.• Freezers should not be overloaded. Refrigerated storage • Refrigerators are used for short-term holding at 41°F or below.• Food must be stored correctly to minimize the possibility of foodborne illness and cross-contamination.• Refrigerated storage temperatures vary from product to product.
    17 : Blast chill refrigeration• Blast chillers are used to quickly cool foods to below 41°F.Deep chill refrigeration• Deep chill refrigeration keeps food at a colder temperature. This may extend the shelf life of the food items. REFRIGERATION STORAGE GUIDELINES:• Use open shelving - this improves air circulation.• Monitor food temperatures and the temperature of the refrigerator.• To hold food at 41°F or less, the refrigerator temperature must be 38°F.• Do not overload the refrigerator.• Store raw products (meat, poultry and fish) separately from (or below) cooked or ready-to-eat foods.• Monitor the temperature of the refrigerator. Create a temperature chart and post by each refrigerator. Temperatures should be recorded each morning and evening.
    18 : FREEZER STORAGE GUIDELINES:• Place frozen food in the freezer as soon as received and inspected.• Use FIFO.• Store food in the original container or tightly wrap to prevent freezer damage.• Keep the freezer at 0°F or below.• Monitor the temperature of the freezer.
    19 : FoodRecommended TemperatureRecommended Maximum Storage Time Our Operation’s Maximum Storage TimeMeatRoast 35-41°F2 - 5 days Ground meat35-41°F1-2 days Sliced ham35-41°F3-5 days Lunch meats35-41°F3-5 days Frozen roasts0-10°F6-9 months Frozen ground meat0-10°F3-4 months Frozen bacon, ham0-10°F2 weeks PoultryChicken, turkey 32-36°F1-2 days Cooked poultry32-36°F1-2 days Frozen chicken0-10°F12 months FishFresh fish 32-36°F1-2 days Frozen fish0-10°F2-3 months EggsShell eggs45°F4-5 weeks Dairy ProductsMilk35-41°F5-7 days after container date Hard cheese (cheddar)35-41°F1 month Dry GoodsFlour 6-8 months Canned fruit 1 year Tea bags 18 months Canned fruit juice 9 months Oatmeal 6 months Rice 2 years Dried beans 1-2 years Potato chips 1 month 
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    21 : Preparation of food for storage Washing Trimming Cutting Blanching Packing in syrup- fruits Packing of meat & seafood.
    22 : Effect of heat treatment on foods Inactivation of plant enzymes Reduction in no. of mo by 99%. Enhancement of color of foods- peas, broccoli,spinach. Wilting of green leafy veg helps to pack them better. Displacement of air from tissues.
    23 : Freezing of foods Sharp freezing- -23.5C SLOW FREEZING--15to -29C FOR 3- 72 HRS Quick freezing-freezing time is as short as 30 mins. Advavtages : Smaller ice crystals formed. Short period for solidification & less diffusion. Prompt prevention of microbial growth. Rapid slowing of food enzymes.
    24 : Changes during & after freezing Deterioration of food Expansion of food Ice crystal formation Binding of water Damages : Freezeburn Color changes Dripping or bleeding Leaking Lethal effects: Cold shock Denaturation Floculation Damage to cell constituents & enzymes.
    25 : end

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