"CANNING" WITH DRY ICE
When dry foods are purchased in large
quantities, they must be stored properly in order to remain edible and pest
free. One method of storage is "canning" with dry ice.
Dry ice is solidified carbon dioxide. Care should be taken when handling it to avoid burns. Hands should be protected by cloth or leather gloves or folded paper when handling it. (Check the yellow pages under "Dry Ice" for sources.)
At room temperature, dry ice will sublimate or turn to gas from its solid form. When dry ice is placed in a container of food, the resultant carbon dioxide forces the oxygen and free moisture out of the container. The remaining atmosphere suffocates insects but does not usually kill any eggs in the food. If the container is kept sealed and airtight, the carbon dioxide will remain and the eggs will not hatch. Over time, the eggs may die. Repeated openings of the container will allow air and moisture to return, however, and eggs may then hatch.
When "canning" with dry ice, approximately 8 ounces of ice is required for 100 pounds of grain; two to three ounces (about a 2-inch cube) per 5 gallon bucket. Place 2 to 3 inches of food in the bottom of the container. Add the dry ice and then pour food over the dry ice to fill the container. Place the lid on loosely. Wait one hour before sealing the lid on. Put the lid on tightly. If the container begins to bulge, "pop" the lid and wait a little longer. An un-"popped" container will explode. Be sure the container lid is on tight before it is stored or carbon dioxide will be lost.
Avoid placing dry ice directly on plastic. The extreme cold could cause the plastic to become brittle and crack. Also, do not use glass containers. The pressure of the gas could cause the glass to shatter.