Frozen foods
Signs of previous thawing include presence of ice crystals, corneas which are opaque, and flesh that does not return to its normal shape when pressed with a finger. Many Arctic communities would preserve food in holes or larders dug into the ice. Fluctuations could occur by a small gap in the freezer door or adding a large amount of unfrozen food. American inventor Clarence Birdseye, who developed the quick-freezing process of food preservation in 1932, is considered the father of the frozen-food industry. The food industry uses a technique called flash freezing, an application of supercooling, to quickly freeze food items.Long-term freezing requires a constant temperature of -18 degrees Celsius (0 degrees Fahrenheit) or less. Many enzyme reactions are only slowed by freezing.
Once-a-month cooking helps cooks save money by purchasing grocery items in bulk and save time by cutting preparation time down considerably. . This causes the water inside the foods to freeze too quickly for large crystals to form, which would destroy the cell membranes and ruin the food. Type of freezers include spiral freezers, tunnel freezers, belt freezers, plate freezers, blast freezers and shock freezers. When foods are individually frozen, they are called individually quick frozen (IQF). Fast food restaurants sometimes use flash freeze on their food and then quickly cook it after. Fish may be sea-frozen or shore-frozen.
The seeds stored may be those of food crops or rare species. An increasingly popular form of home cooking involves preparing a month of meals to store in the home freezer. In this case the food is subjected to temperatures well below the melting/freezing point of water (273 K or 0°C).
Some freezers cannot achieve such a low temperature. Fish in the center of the cartons may not freeze for several hours.
Sea-frozen fish are more expensive. Bulk-frozen fish are packed in cartons which are then placed in blast freezers.
Freezing food is a common method of food preservation which slows both food decay and, by turning water to ice, makes it unavailable for most bacterial growth and slows down most chemical reactions. Freezing only slows the deterioration of food and while it may stop the growth of micro-organisms, it does not necessarily kill them. Frozen food is food preserved by the process of freezing.
There is a tradition in Scandinavia of preserving fish and especially herrings in this way. Cold stores provide large-volume, long-term storage for strategic food stocks held in case of national emergency in many countries. Seeds are stored in freezers at −18 °C or below in seedbanks. Therefore it is common to stop enzyme activity before freezing, either by blanching or by adding chemicals. Foods may be preserved for several months by freezing.
The time food can be kept in the freezer is reduced considerably if the temperature in a freezer fluctuates. For IQF, fish are placed on belts, in chambers, with coolants that freeze in minutes. Frozen fish quality is acceptable if eyes are clear, non-sunken, gills are red, flesh is firm and not broken, and there is little or no odor.
The seeds are stored as a source for planting in case seed reserves elsewhere should be destroyed. Fish are bulk-frozen or individually-quick-frozen (IQF).
