The Technical Side of Storing Food That You Probably Don’t Want to Read, But Read It Anyway!

I’m sorry. Storing food isn’t always about the great sauce you can make with your freeze-dried fruit to put on your ice cream. Sometimes it must be about keeping pest and varmints OUT of your freeze-dried fruit! This blog is all about the technical stuff…how to store it…how to protect it…and why you sometimes have issues with it. Oh, don’t whine. I’ll post some tasty recipes later, ok?


The storage area should be located where the average temperature can be kept above 32°F and below 70°F. Remember that the cooler the storage area the longer the retention of quality and nutrients. Freezing of some items, such as canned products, should be avoided since the expansion of the food during freezing may rupture (metal) or break (glass) the container, or break the seal on lids on glass bottles, and allow the food to be contaminated. This could pose a serious safety risk when the food thaws.

The storage area should be dry (less than 15 percent humidity), and adequately ventilated to prevent condensation of moisture on packaging material. The area should be large enough so that shelves can accommodate all of the stored food and adequate space is available to keep the area clean and tidy. A 9 x 12 foot room with 10 foot ceilings will provide adequate space for a family of six to store an 18 month supply of food. Food should not be stored on the floor. It is a good idea to have the lowest shelf 2-3 feet off the floor in flood prone areas. Shelves should be designed so that a simple rotation system can effectively allow the oldest food to be used first and the newest food to be held within the shelf-life period.

When designing and building a food storage area, do it to minimize areas where insects and rodents can hide. As practical, seal all cracks and crevices. Eliminate any openings which insects or rodents may use to gain entrance to the storage area.

Electrical equipment such as freezers, furnaces and hot water heaters should not be housed in the storage area. These appliances produce heat, unnecessarily increasing storage temperatures. Insulation of the storage area from other areas of the house will effectively reduce the average yearly temperature of the food.

The cooler your storage, the longer the food will maintain quality.


Quality and nutritive value of food deteriorates during storage, therefore foods should not be held for long periods beyond their established shelf-life. When food is stored too long, there is the risk of two things happening: 1) color, flavor, aroma, texture or appearance deteriorate to a level where people will not consume the food, and 2) nutrient deterioration may be severe enough to render the food an unreliable source of specific nutrients.

Properly processed canned, dried, and frozen (never thawed) foods do not become unsafe when stored longer than the recommended time, but palatability and nutrient quality are diminished.



All living systems, whether plant or animal, were designed with a self-destruction mechanism. With death or harvest, this mechanism is activated. If allowed to proceed, naturally occurring enzymes in the food will cause discoloration, and undesirable flavor and textural changes such as when an apple rots. As animals and plants are slaughtered or harvested, they lose the protective devices provided by a living system. When wheat is ground, the kernel dies and becomes vulnerable to rancidity.


Bacteria, yeasts and molds are the most common causes of spoilage of food and food borne illness. Processing methods are designed to control microorganisms by either killing them (ex. canning) or preventing their growth (ex. drying or freezing). It is important to realize that a food which is safe due to inhibition of microorganisms loses that safety when conditions change. Dried beans that are cooked are no longer safe to store at room temperature. When meat is thawed, it still contains living organisms and therefore must be held under refrigeration and used within a fairly short time period.

Insects and Rodents

Rodents deposit waste products in stored grains. Insects grow in flour, hatching eggs, to produce larvae. Cleanliness and good packaging are important in the avoidance of both problems.


Stored food can become unsafe to consume from contact with undesirable substances. Be aware of what nonfood material is in close proximity to the stored food. This includes packaging in nonfood-approved substances such as storing wheat in plastic garbage bags.

Chemical Changes

Flavor and color changes can occur during storage; especially when stored in packages which do not exclude air and light. Baking powder can lose its sizzle and baked products won’t rise.


Shelf-life is defined as the period of time between slaughter or harvest and consumption. Shelf-life may be relatively short (a few hours) or may be extended for a number of months. Scientists determine the shelf-life of a food by storing it under carefully controlled conditions for a given period of time. During this storage period measurements are made to monitor changes in two important parameters: l) the quality of the food (i.e., color, flavor, texture, odor), and 2) the nutrients it contains (i.e., vitamins, protein, fat, water, minerals, and carbohydrate).

There are several important factors which influence shelf-life and are important to consider in a food storage program. Temperature, humidity, packaging material, irradiation by sunlight, the protection from insects and rodents, and formation of natural toxins are just a few of the parameters which must be considered in establishing shelf-life recommendations. Since storage temperature is one of the most important factors, perhaps a general rule might be appropriate. The lower the temperature the longer the shelf-life. Persons storing foods in a garage at an average temperature of 90°F should expect a shelf-life less than half of what could be obtained at room temperature (60-70°F) which in turn is less than half the storage life in cold storage (40°F).

Irradiation by sunlight can also induce physical and chemical changes in food.  Insects and animals can consume food and spread disease. High humidity increases perishability of many foods. Selective packaging material which can exclude light, air, and moisture enhances the length of shelf-life.


While many families have gone to great lengths to insure an adequate store of food in their homes, not much thought has been given to packaging the food.

Food should only be stored in food-grade containers. A food-grade container is one that will not transfer non-food chemicals into the food and contains no chemicals which would be hazardous to human health. Some good examples of containers not approved for food use are trash or garbage bags, paint or solvent cans, industrial plastics and fiber barrels that have been used for non-food purposes. The safety of any packaging material can be determined by contacting the manufacturer and asking if a container is approved for food use. Many manufacturers are beginning to indicate on the container label if it is approved for food use.

Consumers who have stored food in containers other than those approved for food use should dispose of the food immediately. Bury the food deep in the ground where animals do not have access to it. There is no stored food that is worth enough to risk chemical contamination by non-food chemicals and a potential hazard to human health.

Plastic films and containers of food-grade quality are made from polycarbonate, polyethylene and polyester. They differ in characteristics of density, strength and barrier properties. To increase moisture and oxygen barrier properties, films have been laminated. Laminated plastics may include a metallic layer which will greatly increase barrier properties. Military food packaged in metallized polyester, polyethylene wrap has a long shelf life (5+ years) if kept cool.

When safe packaging material has been identified, some suggestions as to size and durability are warranted. Containers for storage of dry foods such as wheat, beans, rice, oatmeal, and cornmeal should have a maximum of 20-30 pound capacity. These sizes may be moved easily by one adult person. More important is that these smaller amounts of food will be used up in a relatively short period, thus reducing the chance for contamination or infestation by insects. Smaller containers provide a way of using the food, but not exposing large quantities to the environment during use periods.

Metal cans used in the canning industry are only designed to last a few years. Losses of canned foods usually occur due to breakdown of the can rather than extensive deterioration of the food under normal storage conditions. Sealed number 10 cans are popular for dehydrated foods mainly due to size, convenience and minimal exposure of the foods to the environment.

Glass jars, which are popular among home caners, are quite inert compared to metal cans, but are less durable to shock. Fiber boxes, which were the original containers for glass jars, make excellent storage containers for jars of fruit since they exclude light and effectively separate individual jars to prevent breakage.

Glass, metal and plastic containers, especially if they have tight-fitting lids and no open crevices or seams, are usually the containers of choice.

If food items, such as grain or cereals, are insect-free when placed in these containers, they will most likely stay insect-free after a long period of storage. Glass jars have the advantage that you can see what’s in them.

Flexible plastic containers last longer and are more durable if placed inside a rigid container. Information on the suitability of flexible plastic containers for protecting food from insect infestations is limited. If the food is insect-free to begin with, and if the packages are properly sealed, they should prove satisfactory.


Non-food household chemicals should not be stored in the same area with food. Volatile chemical compounds can be transferred to the food and affect the flavor and odor. These chemicals should be stored in a separate area where children do not have access to them.

Before using any chemical treatment, check to make sure it is safe to use and determine what levels of the chemical are safe and effective.


Clean, cool, dry storage areas are preferred. Avoid storing food in open containers on shelves. Keep food storage areas free from spilled food and food particles. Good housekeeping helps prevent insect infestations. To prevent or at least minimize insect infestations in stored food products it would be ideal to store them somewhere between 35°F and 45°F. Realistically, if they can be stored below 65°F it will be helpful.

Insects and Animals

In the best interests of the family budget, food conservation, clean food and health, stored food items should be protected from contamination and damage from insect pests.

Small flour beetles, dermestids, weevils, larder beetles, several kinds of moths and other stored food pests readily infest, contaminate, destroy, and consume accessible food supplies. It is important to prevent or reduce these kinds of losses whenever possible.

Prevent Insect Infestations

To prevent insect infestations in bulk foods, keep all stored foods in tight, clean, metal, plastic, or glass insect-proof containers that have tight fitting lids and no open seams or crevices. Store food off the floor and away from damp areas.

Fumigation with Dry Ice Prior to Storage

To fumigate home stored wheat or similar products, spread about 2 ounces of crushed dry ice on 3 or 4 inches of grain in the bottom of the container, then add the remaining grain to the can until it is at the desired depth. If fumigating large quantities use 14 ounces for 100 pounds of grain or 1 pound of dry ice for each 30 gallons of stored grain. At approximately 75 cents a pound for dry ice the cost of fumigating is reasonable.

Since the fumes from vaporizing dry ice are heavier than air, they should readily replace the existing air in the container. Allow sufficient time for the dry ice to evaporate (vaporize) before placing the lid on all the way (approximately 30 minutes). The lid should not be made tight until the dry ice has pretty well vaporized and has replaced the regular air. Then it can be placed firmly on the container and sealed.

Should pressure cause bulging of the can after the lid has been put in place, remove the lid cautiously for a few minutes and then replace it. If using plastic bags in the can, don’t seal the bags until the dry ice has vaporized. Carbon dioxide will stay in the container for some time, provided the container lid is tight. When practical, follow the above procedure in a dry atmosphere to reduce the condensation of moisture in the bottom of the can.

Dry ice tends to control most adult and larval insects present, but probably will not destroy all the eggs or pupae. If a tight fitting lid is placed firmly on the container after the dry ice has vaporized, it may keep enough carbon dioxide inside to destroy some of the eggs and pupae. After 2 to 3 weeks another fumigation with dry ice may be desirable to destroy adult insects which have matured from the surviving eggs and pupae.

If properly done, these two treatments should suffice. Yearly treatments are not indicated unless an infestation is recognized.

Caution: Dry ice should always be handled with care. It should not be accessible to young children or to adults who are not aware of its vaporizing properties.

Chemical Control in Insect Infested Areas

If the infestation is extensive, dispose of the contaminated food. If the infestation is light, you may be able to salvage the product, but in most cases it will be to your advantage to dispose of any insect infested food you have in storage, including spices.

Remove all food packages and containers from the infested area. Clean the shelves, and as appropriate, remove the lower kitchen drawers and clean the areas behind and underneath the drawers with an extension to the vacuum. Then spray the area with a house- hold formulation of an approved insecticide such as pyrethrum or Malathion. If an aerosol formulation is used, the dosage should be no problem. If mixing a concentrated insecticide with water, follow label directions. Spray cracks and crevices under shelves and along mop boards. Do not spray the insecticide directly on food, food preparation surfaces, such as bread boards, or on any food equipment or utensils. If appropriate, once the spray dries, cover the shelves with clean shelf paper or foil before returning food packages to the shelves.

Kerosene-based sprays should not be used around flour since the flour may absorb the kerosene. If treating an area where flour is stored, remove the flour before treating and place it back on the shelves after the kerosene odor is gone. Do not spray oil-based insecticides on asphalt-tile floors.

Household formulations of Diazinon, Baygon (propoxur), Malathion, or Drione, may be used for crack and crevice treatment behind radiators, under sinks, and in ant runs to destroy ants, roaches, earwigs, silverfish and roaming flour-infesting insects. See label directions for information on insects controlled by these chemicals and the appropriate uses.

NOTE: Most insecticides are poisonous to man and animals. Follow instructions on the label. Do not store pesticides near foods or medicines. Keep all pesticides out of the reach of children, pets, and livestock.

Physical Methods of Controlling Insects in Food

Clean, cool, dry storage areas are preferred. Avoid storing food in open containers on shelves. Keep food storage areas free of spilled food and food particles. Good housekeeping helps prevent insect infestations.

Deep Freeze Control for Grain

Small quantities of grain, 1 to 10 pounds, can be put in medium to heavy food grade plastic bags and placed in a deep freeze for 2 to 3 days. This will usually destroy all stages of any insect pests which are present.

As a check spread the deep freeze treated grain on a cookie tray at room temperature until thawed. If live insects are present they will probably be seen crawling about. If they are present, repeat the process. If not, remove any insect fragments, put the grain in an approved container and store it in a cool, dry place.

Heat Treatment—Air

When packaged goods such as beans, cereals, whole grains, nut meats, and similar dried foods become infested they may be “sterilized” by heating in an open oven as follows.

Spread a shallow layer of wheat in a cookie tray or large pan. Pre-heat the oven to about 140° to 150°F. Put the tray in the preheated oven and leave it there for 30 minutes or more. The oven door should be left slightly open to avoid overheating. This treatment should destroy all stages of the insect if the layer of grain on the tray is not too thick (1/2 inch). Next, remove the tray and cool the wheat thoroughly before returning it to a clean, dry storage container. As necessary, use a fan to blow off any existing insect fragments. Where large quantities of dry food are to be treated, this method is not practical.

Heat is detrimental to the proteins in wheat and may reduce the ability of the bread to rise properly. Some reduced loaf volume and heavier texture may be apparent when using heat treated grains.

Dry Ice

Food may be fumigated with dry ice as previously described.


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