(Storage for more than 5 years)
To prepare dry (10% or less moisture) food for long-term storage, oxygen should be removed from or replaced in containers. There are five kinds of containers that can be used:
- #10 metal cans
- Heavy foil laminated pouches
- Glass canning jars
- PETE bottles
- HDPE plastic buckets
All five kinds of containers should be stored in a relatively cool, dry, and dark environment for the longest shelf-life.
Oxygen absorbers protect dry foods from insects and help maintain food quality during storage. They are small packets of iron filings or powder. The packet material allows oxygen and moisture in but keeps the iron from coming out. Moisture in the food causes the iron in the packet to oxidize or rust. As the iron rusts, it uses the oxygen in the container. Note: oxygen-free storage does not affect seed viability. Seeds, whole grains, and beans will still sprout.
Enamel lined #10 metal cans are filled with dry food, an oxygen absorbing packet is added, and the can is sealed with a can sealer. Cans can be stored in a small amount of space and should be stored where they are not in direct contact with floors and walls. Cans are impermeable to light, moisture, air, and insects, but they will eventually rust when stored in humid climates. When a can is opened, a plastic lid should be put on it or the contents transferred to a container with a lid. Each can will hold about 13 cups of food. Used cans cannot be reused for canning without using a flanging tool to cut and reshape the edge of the can. Note: plastic lids are not impermeable to humidity or insects.
Heavy foil laminated pouches made of multi-layer laminated plastic and aluminum are filled with dry food, an oxygen absorbing packet is added, and the pouch is sealed with an impulse sealer. Pouches that are 7 mil thick are not easily punctured but can still be chewed through by rodents. The pouch is impermeable to light, moisture, air, and insects. They can be slid into shorter spaces than #10 cans, stacked in boxes or bins, put in plastic buckets, or placed on a shelf. Pouches should not be stored in containers that have been used to store nonfood items. Once the pouch is open, the contents should be transferred to another container with a lid and stored on a shelf or in a cupboard. The 12” by 13-1/2” pouches comfortably hold 1 gallon (16 cups). Used pouches can be washed, dried, and reused but will hold less food each time they are reused since they are cut down to open them. (See “Using a Tabletop Impulse Sealer”)
Glass canning jars are filled with dry food, an oxygen absorbing packet is added, the jar edge is wiped clean and a new, clean, warm, and dry canning lid and ring are screwed on tightly. Glass is impermeable to moisture, air, and insects. Jars should be stored away from light and in a way that protects them from breakage. They can be stored in a short space such as under beds. Once opened, jars are usually small enough to store in a cupboard or on a pantry shelf where the contents are easily seen. When the jars are reused, a new lid should be used if the used one is bent or damaged in any way. (See “Dry-Pack Canning in Glass Canning Jars”)
Clean, dry plastic PETE (polyethylene terephthalate) bottles are filled with dry food, an oxygen absorbing packet is added, the mouth edge wiped clean, and the lid screwed on tightly and taped down with masking or packing tape. PETE bottles that have previously held liquids are the best to use because they have the correct kind of lid. The inside of the lid must feel rubbery and not hard so that an airtight seal can be obtained. PETE bottles can be identified by the embossed recycling symbol on the bottom of the bottle. There will be a “1” inside a triangle and either “PET” or “PETE” next to it. PETE is virtually oxygen impermeable and will protect from moisture and insects. PETE bottles should be stored away from light and protected from rodents. They can often be stored in a small amount of space and are convenient to keep in the pantry or cupboard because the contents can be easily seen and the bottle is easy to handle. Use PETE bottles for long-term storage of foods such as wheat, corn, and dry beans. (See “Dry Packing in PETE Bottles”)
Because food grade HDPE (high density polyethylene) plastic buckets are oxygen and nitrogen permeable, dry food must be packed in one of two ways for long-term storage.
- A thin laminated foil bag is placed inside a clean bucket, the bag is filled with food, and oxygen absorbers are put in (one 300 cc absorber for each gallon of food). The bag is sealed by using a handheld impulse sealer or by placing a wood board on one edge of the bucket, folding the top of the bag over the board, and ironing the bag until it is sealed. The top of the bag is then folded into the bucket. The bucket lid is secured by hammering around the outside edge with a hammer or mallet. The commercially prepared version of this is sometimes called a “super pail.”
- A 2 to 3-inch layer of food is placed in the bottom of a clean bucket and dry ice is added (4 ounces for 5 gallons). The bucket is filled with food to within 1-inch of the top and the lid loosely attached. The dry ice is allowed to sublimate (change to gas) for about 1 hour or until the bottom of the bucket is no longer very cold. The lid is secured and the bucket watched for bulging for a short time. If the lid or sides bulge, the lid should be lifted slightly to allow gas to escape and then resealed. When the bucket no longer bulges, it is safe to store. (See “Dry Ice Treatment in Plastic Buckets”)
Buckets should be opaque (especially when using dry ice since they are not lined with mylar) to protect food from light. They should be new or, if used, should have stored only food previously. They are impermeable to moisture and insects when they have a gasketed lid. When packed using one of the above methods, they also protect from the air. To open buckets, cut through the marked slits on the sides of the lid (being careful to avoid cutting the gasket) or pull off the scored edge of the lid and pull up sections until the lid comes off. Lid lifting tools are also available. Some lids have a round opening with an attached spout and lid for pouring out the contents without removing the main lid. Frequently used buckets can have the lid replaced with a gamma seal lid (a 2-piece lid with a removable inner portion) for ease of use. Gamma lids should not be used for long-term storage.
Buckets should not be stored directly on cement. They should rest on racks or pieces of wood to allow air to circulate underneath and prevent the cement from sweating. Avoid stacking them more than 3 high especially without boards between the layers or the center of the lid may crack and break.