Oxygen Absorbers For Your Emergency Food Supplies: "During the season for many fresh fruits and vegetables, I buy organics at the farmers' markets in quantity and dehydrate them at home for use throughout the off-season. Occasionally, in the past, I have had some of my dehydrated foods spoil due to moisture finding its way into the (supposedly airtight) jars. Since water is two parts hydrogen and one part oxygen, moisture cannot form if either component is missing. Hence oxygen absorbers. I have not had a single failure since I began using them. They're not terribly exciting, but they are effective and I recommend them for anyone who dehydrates foods.
Another mistake I have learned is that even though food is dehydrated, and kept in air tight jars, doesn't mean the food is free from mold. With the air that is existent in the containers, mold will develop."