"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"
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.