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Four Factors that Effect Shelf Life

Determining the storage life of foods is, at best, an inexact science as there are so many variables. These range from the condition your food was in when you first purchased it and includes many other factors. This page was written with input by Mr. Stephen Portela who has over 30 years of professional food storage experience. This information should be used as a general guide only, and should not be followed "as the gospel truth" because your results may be different.

Factor 1: Temperature If you are planning on storing your food in a warm environment, it will only last a fraction of the time it would last if stored in a cool, dry place. You can expect good storage life if your storage temperature is at 60F or below. Optimum storage temperature is at 40F or less. It is important you also find a place where the temperature remains constant. Frequent temperature changes shorten storage life. If you don't have a cool place for your food storage, plan on rotating your storage quickly enough to prevent food loss.

Factor 2: Moisture Foods with excess moisture can spoil in their containers. This is an important consideration when packing food with dry ice as moisture condenses and freezes on the outer surface of the dry ice. For long-term storage, grains should have moisture content of 10% or less. It is difficult to accurately measure this without special equipment. It is also important to know that you can not dehydrate foods at home that reach these levels. Food that is dried to a moisture level of 10% moisture crisply snap when bent.

Factor 3: Atmosphere Foods packed in air don't store as well as in oxygen-free gasses. This is because air contains oxygen, which oxidizes many of the compounds in food. Bacteria, one of several agents that makes food go rancid, also needs oxygen to grow. Food storage companies have a couple of different processes for removing oxygen:

  • Displacing oxygen: This is done by purging out all the air in the product with an inert gas. Nitrogen is almost always used because it is the most inert gas known. People doing their own packing occasionally use dry ice which gives off carbon dioxide gas, and probably works just about as well.

  • Absorbing oxygen: Air contains about 78% nitrogen and 21% oxygen, leaving about 1% for the other gasses. Oxygen absorber packets leave about 99% pure nitrogen in a partial vacuum. If oxygen absorber packets are used, care must be taken to use a storage container that can stand some vacuum.
Factor 4: Container To get the best storage life out of your product it must have a hermetic (air tight) seal. Containers that do this well are:
  • Sealable food storage buckets

  • Sealable food quality metal (lined) or plastic drums

  • #10 Cans (Use only cans that are enamel lined, otherwise your food flavor will be tainted by the steel it comes in contact with. An enamel lined can also prevents the inside of the can from rusting.)

Whatever container you use, be sure it is food grade as your product can be tainted with whatever the container is made from. Plastic sacks are not good airtight containers, for even if they are sealed, the relatively thin plastic 'breathes,' allowing air to pass through. Paper sacks are even worse.

Al Durtschi,
Copyright 1996, Al Durtschi. All rights reserved.

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