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Food storage

Food storage is both a traditional domestic skill, and an important industrial specialty.

Domestic food storage

The smallest practical grain storage systems use closed-top #10 metal cans. A block of dry ice is placed in the bottom, the can is filled with grain. The can is then "burped" of excess gas. The carbon dioxide from the sublimation of the dry ice prevents insects, mold, and oxidation from damaging the grain. Grain stored in this way can survive five years in a moist garage.

Storage in grain sacks is not effective. Mold and pests destroy a 25kg cloth sack of grain in year, even if stored off the ground in a dry area. On the ground or damp concrete, the time is as little as three days, and the grain might have to be dried before it can be milled. Do not buy any form of bulk dry food until after the storage vessels are available.

Fruits and vegetables can be scalded, and then frozen in air-tight bags to prevent sublimation damage ("freezer burn").

If refrigeration is not desired, one can use a root cellar, canning and pickling.

Root cellars and spring houses are effective in temperate climates where the average ground temperature several feet below the surface is less than 15C (60F). A traditional root cellar is a masonry (usually concrete) storage area (often in a basement) with roof and house-side wall, if any, insulated, and outside walls insulated to the depth at which ground temperature has no seasonal changes. Farmers improvise large root cellars by bulldozing a 1-1.5M cut, wrapping produce in plastic sheets and placing them in the cut, and bulldozing 1..1.5M of cold subsurface dirt over them.

Spring houses are very similar to root cellars, except that the cold water from a natural spring is used to cool a (usually metal) bucket or storage area.

Canning varies by product, and is a subject unto itself. The basic principle is to heat the food to a high enough temperature to kill bacteria, yet not so high or so long as to damage vitamins and color. Meats, especially shellfish and seafood, are the most difficult and dangerous items to can. Following instructions for particular foods is recommended. A pressure cooker is very helpful for achieving the brief high temperatures that give the best results.

Pickling is a practical, safe alternative to canning most fruits and vegetables, and preserves more vitamins. Although flavors are less pleasant for most people, fuel costs and the danger of bacterial poisoning are far less.

Drying is often used for foods whose greatest value is as energy or protein. Common foods of this sort are jerkeys, trail biscuit, dried fruits and cheese. Drying or curing (osmotic drying by contact with a water-absorbing substance) is often combined with pickling.

Freeze-dried foods are frozen and then dried by sublimation in a vacuum. While this is not practical to do at home, commercial bulk freeze-dried nitrogen-packed foods are an excellent addition to a pantry. They provide good-quality vegetables, fruits and prepared foods that require no refrigeration, and ease the difficulty of preparing meals from a long-term storage pantry.

A number of programs recommend acquiring a limited range of grains (usually corn, wheat and beans supplemented with oil, dried milk and vitamins) and then preparing them in simple ways for long-term survival during emergencies. This is not practical because of appetite exhaustion. An unvarying diet of staples prepared in the same way causes most people to eat less, and roughly 90 days after beginning such a diet, people will begin to starve to death from a lack of desire to eat. Garden-grown fruits and vegetables, freeze-dried, canned, and fresh-baked foods are essential supplements to such a program.

A special virtue of bulk foods is their low cost. Costs of dry bulk foods (before preparation) are often less than 1/4 of convenience and fresh foods purchased at supermarkets.

Commercial food storage

Grain and beans are stored in tall grain elevators, almost always at a rail head near the point of production. The grain is shipped to a final user in hopper cars. In the soviet russia, where harvest was poorly controlled, grain was often irradiated at the point of production to suppress mold and insects. In the U.S., threshing and drying is performed in the field, and transport is nearly sterile and in large containers that effectively suppress pest access, so irradiation is not required. At any given time, the U.S. usually has about two weeks of stored grains.

Fresh fruits and vegetables are either packed in plastic cups in cardboard boxes for fresh premium markets, or placed in large plastic tubs for sauce and soup processors. Fruits and vegetables are usually refrigerated at the earliest possible moment, and even so have a shelf life of two weeks or less.

COmmercial freeze-drying is widely used for soups and drinks, and there is a thriving but small market in bulk vegetables and convenience foods for campers.

Meats are usually transported live, slaughtered at a major distribution point, hung and transported for two days to a week in refrigerated rail cars, and then butchered and sold locally. Before refrigerated rail cars, meat had to be transported live, and this placed its cost so high that only farmers and the wealthy could afford it every day.