When storing foods like rice, beans, wheat, etc., a key factor for successful long term storage is to remove the oxygen from the environment.
Oxygen enables bad things to happen to your food over time. Spoilage organisms will grow, possible molds, rancidity, oxidation of vitamins, condensation, and bugs are just some of the bad things that could happen to your food in an oxygen friendly environment.
A solution to this problem is to use oxygen absorbers. What is an oxygen absorber? It is typically a packet consisting of powdered iron oxide. It is safe, and very effective so long as you use at least the right amount.
Air (on Earth) contains 21% oxygen. Using the proper quantity of oxygen absorbers will reduce the oxygen levels to .01%, effectively eliminating the risk of nastiness in your food storage.
There is a caveat to effectiveness however. The container MUST be air-tight. This may sound like a no-brainer, but some containers simply don’t hold a vacuum like you might think. For example, plastic will ‘breath’ over time. By the way, always use food-grade plastics if the food will be touching it.
Arguably one of the best methods of air-tight storage is to use mylar bags, which can be sealed and then stored within a 5-gallon bucket. The mylar will provide an air-tight seal (if sealed properly) and the bucket will provide protection for puncture or rodents.
Oxygen absorbers themselves come shipped in a sealed bag. Remember, once you open that sealed bag, the absorbers will start absorbing the oxygen of the air around it. So don’t leave them sitting around for long (no more than 30 minutes).
Have your food ready to go and already packed in the mylar bags, ready to seal. Use what you need and then save the rest in an air-tight container. You could use a vacuum sealer and bag for the remaining O2 absorbers, or you might keep them in a canning jar with an air-tight lid (fill the remaining air space inside with rice).
Oxygen absorbers are rated in ‘cc’. The sizes of oxygen absorbers correspond to the amount of oxygen they absorb. For example, a 300 cc oxygen absorber will absorb 300 cc of oxygen. So the key to knowing how big of an oxygen absorber to use, is to know how much total air (oxygen) it will need to absorb… which is the head space air plus the air that’s all around the individual pieces of food, called void space (in cc’s or cubic centimeters).
To determine the total residual air that will remain in your storage container (sealed mylar bag), you could apply a moderately complicated procedure and formula, or you could follow some general advice based on other people’s experiences and others who have run the formula. Out of practicality, I’m going to skip detailing the formula and list what has worked for others…
As an aside, since this stuff is not expensive and the value of long term food storage could be VERY valuable if you ever really need it, I prefer to err on the side of caution and use a little more O2 absorbers than the exact right amount.
For rice, beans, or wheat in sufficient size mylar bag to be contained within a 5 gallon bucket, use 2000 cc worth of oxygen absorbers. This leaves a bit of a safety margin which is important for larger size items such as beans because they have a bigger void space.