Shelf Life for Food Storage
The Family Survival Planning web site distinguishes two ways of defining "Shelf Life":
1. The "Best if used by" date for best taste and nutrition
2. A "Life Sustaining" date where the food may not taste wonderful but it will keep you alive.
The life sustaining period is influenced by temperature, moisture, oxygen and light.
* Temperature - the cooler the better, above freezing. Heat destroys food and its nutritional value, while foods stored below freezing will suffer freezer burn. A storage area should never exceed 75°; optimal is 50° to 60°.
* Moisture in food allows bacteria and other microorganisms to grow. Hence many long-term storage foods are freeze-dried or dehydrated.
* Oxygen in stored food also encourages microorganisms. When my wife & I stored wheat, we added an oxygen absorber packet to each storage bucket. Oxygen is also the enemy of fats and oils causing them to go rancid. Nuts, grains, and other long-term foods contain some natural oils. Whole grains have an outer shell that protects the oil inside and can last 30 years or more, but ground flour exposes the oils and goes rancid in 5 years.
* Light can destroy the color in food and promote microorganisms growth.
Check out the Long Term Food Shelf Life Chart at FSP. I was surprised to learn that dried apple slices and dried potatoes can last 30 years. Powered milk for 20yrs? Hmm, I'd worry about it going rancid sooner.