question: What changes happen to any foods that it is generally considered not fresh once frozen?
comment: When you freeze things the ice Crystals in the food cut open the cells when it thaws the texture is mush
passages: The length of storage depends on the method used but is usually five days. For longer storage the food may be subjected to pasteurization after cooking.
   Temperature data loggers and time temperature indicators can record the temperature history of a shipment to help estimate their remaining shelf life.
  
  According to the USDA, "foods kept frozen continuously are safe indefinitely."
  
  Section::::Packaging.
   BULLET::::- Vitamin B (Thiamin): A vitamin loss of 25 percent is normal. Thiamin is easily soluble in water and is destroyed by heat.
  
  BULLET::::- Vitamin B (Riboflavin): Not much research has been done to see how much freezing affects Riboflavin levels. Studies that have been performed are inconclusive; one study found an 18 percent vitamin loss in green vegetables, while another determined a 4 percent loss. It is commonly accepted that the loss of Riboflavin has to do with the preparation for freezing rather than the actual freezing process itself.
   In general, boiling vegetables can cause them to lose vitamins. Thus, the process of blanching does have deleterious effects on some nutrients. In particular, vitamin C and folic acid are susceptible to loss during the commercial process, and canned or frozen broccoli for instance loses the entirety of its most valuable nutrient. In addition, studies have shown that thawing frozen vegetables before cooking can accelerate the loss of vitamin C.
   Frozen vegetables
  
  Frozen vegetables are vegetables that have had their temperature reduced and maintained to below their freezing point for the purpose of storage and transportation (often for far longer than their natural shelf life would permit) until they are ready to be eaten. They may be commercially packaged or frozen at home. A wide range of frozen vegetables are sold in supermarkets.
   BULLET::::- Oxygen generators
  
  Section::::Effects on nutrients.
  
  Section::::Effects on nutrients.:Vitamin content of frozen foods.
   The freezing process tends to degrade the taste of food and the meals are thus heavily processed with extra salt and fat to compensate. In addition, stabilizing the product for a long period typically means that companies will use partially hydrogenated vegetable oils for some items (typically dessert). Partially hydrogenated vegetable oils are high in trans fats and are shown to adversely affect cardiovascular health. The dinners are almost always significantly less nutritious than fresh food and are formulated to remain edible after long periods of storage, thus often requiring preservatives such as butylated hydroxytoluene. There is, however, some variability between brands.
   Freezing is an effective form of food preservation because the pathogens that cause food spoilage are killed or do not grow very rapidly at reduced temperatures. The process is less effective in food preservation than are thermal techniques, such as boiling, because pathogens are more likely to be able to survive cold temperatures rather than hot temperatures. One of the problems surrounding the use of freezing as a method of food preservation is the danger that pathogens deactivated (but not killed) by the process will once again become active when the frozen food thaws.
   Preserving food in domestic kitchens during modern times is achieved using household freezers. Accepted advice to householders was to freeze food on the day of purchase. An initiative by a supermarket group in 2012 (backed by the UK's Waste & Resources Action Programme) promotes the freezing of food "as soon as possible up to the product's 'use by' date". The Food Standards Agency was reported as supporting the change, providing the food had been stored correctly up to that time.
  
  Section::::Classifications and types of food.:Functional food.
   Alternative methods for preserving herbs include freezing in water or unsalted butter. Herbs can be chopped and added to water in an ice cube tray. After freezing, the ice cubes are emptied into a plastic freezer bag for storing in the freezer. Herbs also can be stirred into a bowl with unsalted butter, then spread on wax paper and rolled into a cylinder shape. The wax paper roll containing the butter and herbs is then stored in a freezer, and can be cut off in the desired amount for cooking. Using either of these techniques, the herbs should be used within a year.
   Some foods, such as bananas, are picked when unripe, are cooled to prevent ripening while they are shipped to market, and then are induced to ripen quickly by exposing them to propylene or ethylene, chemicals produced by plants to induce their own ripening; as flavor and texture changes during ripening, this process may affect those qualities of the treated fruit.
  
  Section::::Chemical composition.
   Section::::Dried foods.:Processed foods.:I (i).
  
  BULLET::::- Freeze-dried ice cream is ice cream that has had most of the water removed from it by a freeze-drying process; sealed in a pouch, it requires no refrigeration. It achieved fame as a popular food in human spaceflight.
  
  Section::::Dried foods.:Processed foods.:J.
  
  BULLET::::- Edible jellyfish is often salt cured, creating a dried finished product.
  
  Section::::Dried foods.:Processed foods.:K.
   The speed of the freezing has a direct impact on the size and the number of ice crystals formed within a food product's cells and extracellular space. Slow freezing leads to fewer but larger ice crystals while fast freezing leads to smaller but more numerous ice crystals. Large ice crystals can puncture the walls of the cells of the food product which will cause a degradation of the texture of the product as well as the loss of its natural juices during thawing. That is why there will be a qualitative difference observed between food products frozen by ventilated mechanical freezing, non-ventilated mechanical freezing or cryogenic freezing with liquid nitrogen.
   Frozen vegetables have some advantages over fresh ones, in that they are available when the fresh counterpart is out-of-season, they have a very long shelf life when kept in a freezer and that they often have been processed a step or more closer to eating. In many cases, they may be more economical to purchase than their fresh counterparts.
  
  The history of frozen fruits can date back to the Liao Dynasty of China, with the "frozen" pear being a classic delicacy eaten by the Khitan tribes in the Northeastern region of China.
  
  Section::::Health benefits and risks.
   Preserving food in domestic kitchens during modern times is achieved using household freezers. Accepted advice to householders was to freeze food on the day of purchase. An initiative by a supermarket group in 2012 (backed by the UK's Waste & Resources Action Programme) promotes the freezing of food "as soon as possible up to the product's 'use by' date". The Food Standards Agency was reported as supporting the change, providing the food had been stored correctly up to that time.
  
  Section::::Preservatives.
   Frozen products do not require any added preservatives because microorganisms do not grow when the temperature of the food is below , which is sufficient on its own in preventing food spoilage. Long-term preservation of food may call for food storage at even lower temperatures. Carboxymethylcellulose (CMC), a tasteless and odorless stabilizer, is typically added to frozen food because it does not adulterate the quality of the product.
  
  Section::::History.
  
  Natural food freezing (using winter frosts) had been in use by populations in cold climates for centuries.
   Freezing is also one of the most commonly used processes, both commercially and domestically, for preserving a very wide range of foods, including prepared foods that would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but potatoes themselves require only a cool dark place to ensure many months' storage. Cold stores provide large-volume, long-term storage for strategic food stocks held in case of national emergency in many countries.
  
  Section::::Traditional techniques.:Boiling.
   Cryogenic or (flash freezing) of food is a more recent development, but is used by many leading food manufacturers all over the world. Cryogenic equipment uses very low temperature gases – usually liquid nitrogen or solid carbon dioxide – which are applied directly to the food product.
  
  Section::::Packaging.
  
  Frozen food packaging must maintain its integrity throughout filling, sealing, freezing, storage, transportation, thawing, and often cooking. As many frozen foods are cooked in a microwave oven, manufacturers have developed packaging that can go straight from freezer to the microwave.
   Throw out foods that have been warmer than for more than 2 hours. If there is any doubt at all about the length of time the food has been defrosted at room temperature, it should be thrown out. Freezing does not destroy microbes present in food. Freezing at 0 °F does inactivate microbes (bacteria, yeasts and molds). However, once food has been thawed, these microbes can again become active. Microbes in thawed food can multiply to levels that can lead to foodborne illness. Thawed food should be handled according to the same guidelines as perishable fresh food.
   Food frozen at 0 °F and below is preserved indefinitely. However, the quality of the food will deteriorate if it is frozen over a lengthy period. The United States Department of Agriculture, Food Safety and Inspection Service publishes a chart showing the suggested freezer storage time for common foods.
  
  Section::::Domestic food storage.:Food storage safety.:Refrigeration.
  
  It is important to note that safe food storage using refrigeration requires adhering to temperature guidelines:
  
  Section::::Domestic food storage.:Food storage safety.:Storage times for refrigerated food.
  
  The United States Department of Agriculture, Food Safety and Inspection Service publishes recommended storage times for refrigerated food.
   Section::::Applications of freeze drying.:Freeze drying of food.:Coffee.
  
  Coffee contains flavor and aroma qualities that are created due to the Maillard reaction during roasting and can be preserved with freeze-drying. Compared to other drying methods like room temperature drying, hot-air drying, and solar drying, Robusta coffee beans that were freeze-dried contained higher amounts of essential amino acids like leucine, lysine, and phenylalanine. Also, few non-essential amino acids that significantly contributed to taste were preserved.
  
  Section::::Applications of freeze drying.:Freeze drying of food.:Fruits.
   Freezer temperature should be maintained below . Food should never be thawed at room temperature, this increases the risk of bacterial and fungal growth and accordingly the risk of food poisoning. Once thawed, food should be used and never refrozen. Frozen food should be thawed using the following methods:
  
  BULLET::::- Microwave oven
  
  BULLET::::- During cooking
  
  BULLET::::- In cold water (place food in watertight, plastic bag; change water every 30 minutes)
  
  BULLET::::- In the refrigerator
   Shelf-life extension is a result from low processing temperatures in conjunction with rapid transition of water through sublimation. With these processing conditions, deterioration reactions, including nonenzymatic browning, enzymatic browning, and protein denaturation, are minimized. When the product is successfully dried, packaged properly, and placed in ideal storage conditions the foods have a shelf life of greater than 12 months.
  
  Section::::Advantages.:Re-hydration.
   BULLET::::- at room temperature; this is dangerous since the outside may be defrosted while the inside remains frozen
  
  BULLET::::- in a refrigerator
  
  BULLET::::- in a microwave oven
  
  BULLET::::- wrapped in plastic and placed in cold water or under cold running water
  
  People sometimes defrost frozen foods at room temperature because of time constraints or ignorance; such foods should be promptly consumed after cooking or discarded and never be refrozen or refrigerated since pathogens are not killed by the freezing process.
  
  Section::::Quality.
   Chicken can be cooked or reheated from the frozen state, but it will take approximately one and a half times as long to cook, and any wrapping or absorbent paper should be discarded. There are three generally accepted safe methods of reheating frozen chicken: in the refrigerator, in cold water, or using a microwave oven. These methods are endorsed by the FDA as safe, as they minimize the risk of bacterial growth. Bacteria survives but does not grow in freezing temperatures. However, if frozen cooked foods are not defrosted properly and are not reheated to temperatures that kill bacteria, chances of getting a foodborne illness greatly increase.
  