Introduction

Moisture and oxygen are two of the most important factors in spoilage or deterioration of stored foods. Moisture in dried foods can lead to microbial growth.  Moisture around metal canned foods could lead to rust and an eventual compromise of the can.  Oxygen is an important factor in quality deterioration of many foods.  To store foods over a prolonged period requires packaging that resists moisture and oxygen transfer.  Foil pouches or bags, glass canning jars, plastic PETE bottles, and plastic buckets are some common acceptable storage containers. 

Foil pouches

Polyethylene terephthalate (PET or PETE) and foil laminate pouches are exceptional food containers.  The polyethyene (PET) layer is food-grade plastic with no known toxicities.  The foil layer dramatically reduces the transmission of oxygen and moisture through the film.  One trade name is Mylar and its often used as a generic name.  Be aware that even though there is a metallic layer in the bag, rodents can easily chew into them.  These bags come in many different sizes including one that fills a 5 gallon bucket (approx. 18"x28").  The 1 gallon bag holds approx. 7 pounds (3.2 kg) of wheat, 6.8 pounds (3.1 kg) of white rice, or 5 pounds (2.3 kg) of dry milk.  Bags should be sealed using a heat sealing unit after first using oxygen absorbers to minimize oxygen.  Sealing with an iron is not recommended due to a poor seal.  Vacuum sealers may work for a few food types, however, powders and some granular products are not easily vacuum packaged.  Remember, vacuum sealing is only safe for dry foods.  Vacuum sealing moist foods may lead to botulism food poisoning.

Mylar-type PET bag	Glass Canning Jar	PET Bottle	Metal Cans

Glass canning jars with screw-on lids

All glass jars used to can foods work well for storing dry foods provided a tight sealing lid is used, e.g. mayonnaise jars. However, only mason-type canning jars with two-piece lids can be used safely for home canning foods in jars.  Be sure jars are thoroughly cleaned of all previous food residue before using it for food storage.  Mason jars with metal lids are an excellent barrier to oxygen and can be used for long term storage of foods.

Plastic (PETE) Bottles

PETE is the same plastic in foil pouches molded to form rigid bottles.  The bottles are identified on the bottom, next to the recycle emblem, with the letters PET or PETE. This type of container has acceptable short-term (1-2 years) oxygen barrier qualities and can be used with oxygen absorbers to store bulk dry foods. The low oxygen content of the sealed containers protects the stored food from insect infestation and helps preserve product quality. These containers are well suited for products that are rotated on a regular basis, while still providing a few years of storage capability. Use only PETE bottles that have been previously commercially packaged with food. Bottles need to have screw-on lids with plastic, not paper or foam, lid seals. Verify that the lid seal will not leak air by placing a sealed empty bottle under water and pressing on it.   Wash and rinse bottles to remove any residue. Drain and dry bottles.   Place an oxygen absorber packet into each bottle.  Fill bottles with bulk dry products that are low in moisture and oil content.   Wipe top sealing edge clean.   Screw lids on tightly. Tape the lid edge to prevent loosening. 

Metal Cans

Metal cans will have a near zero oxygen transfer rate and are great for very long term storage (30 years).  Packing foods in metal cans for storage is the most expensive method if done at home.  The cans are relatively inexpensive, but they cannot be re-used.  The cans MUST be made for foods and lined with food grade enamel.  While the cans are inexpensive, a can sealer can cost approx. $1000.  For this reason metal cans are best reserved for a Food Storage Cooperative type operation.  Number 10 cans are the most common.  It is approximately .82 gallon. The weight varies by product. For example, a #10 can holds 5.8 pounds (2.6 kg) of wheat, 5.7 pounds (2.6 kg) of white rice, or 4.1 pounds (2.3 kg) of nonfat, instant dry milk.

Food Grade Plastic buckets

Another common and easy to use container is the food grade plastic bucket with lid.  They are made of high-density polyethylene (HDPE).  HDPE will have a slow oxygen transfer rate that can allow oxygen in over several years.  A general rule of thumb is that these buckets will store foods for up to five years.  The 5-6 gallon size is common and useful for larger quantities of foods.  Lids should have a sealing gasket to form an air tight seal.  Some lids can only be used once and may disfigure after opening.  A reusable lid has been created called gamma seal.  These are available from specialty stores.  Another nifty gadget is the bucket wrench.

HDPE Bucket	Bucket wrench	Gamma Lid

Important Notes

Convenience and price aside, the best container choice for long term storage would be the foil-type pouch (bag).  Vacuum package or seal dried foods inside with oxygen absorbers.  Place these bags inside a 5 gallon bucket or similar container that is a barrier to rodents.  The second best is metal cans for the sole reason that they can rust over time.  Be sure any packaging choice is food grade.  When in doubt, assume it is not food grade. Food grade plastics are tested so that they do not leach chemicals into foods during normal use.  If reusing containers, do not reuse those that contained non-food items.  Be aware that only metal is impervious.  All plastics will allow some gas and chemical transfer, although slowly.  Therefore, store all containers off the floor.  It is possible that volatile compounds from flooring or raw concrete can slowly permeate containers.

References: 

¹ 21 CFR 177

²  FDA’s Center for Food Safety and Applied Nutrition: http://www.cfsan.fda.gov/~dms/opa-indt.html

³  Castle, L.  Migration of Polyethylene Terephthalate PET Oligomers from PET Plastics into Foods During Microwave and Conventional Cooking and into Bottled Beverages. Journal of Food Protection; 1989, 52 (5): 337-342.

⁴  Packaging Materials: 1. Polyethylene Terephthalate (PET) for Food Packaging Applications. International Life Sciences Institute; 2000, Washington, DC, p. 11.

⁵  White Paper on Refillable Plastic Packaging Made from PET (Polyethylene Phthalate). International Life Sciences Institute (ILSI) – North America; 1994, p.58.