Five-gallon plastic buckets are good for storing bulk products such as wheat, rolled oats, and beans. Be sure to use food-grade buckets that were designed for food storage. These buckets are always white or opaque. Do not use plastic buckets that have been used for chemical storage. Plastic buckets are useful for long-term storage. Although they are not airtight, if they are flushed with carbon dioxide or sealed with dry ice, that will help to destroy any insects that may be present in the food.

Carbon dioxide effectively prevents weevil infestation in dry-pack items stored in plastic buckets. To kill weevils, carbon dioxide should be present in concentrations above 3 percent. Treatment methods that depend on the absence of oxygen to kill weevils, such as oxygen absorbers and nitrogen gas flushing, are not always effective in plastic buckets because of the potential for oxygen leakage.

Instructions for Dry Ice Treatment in Buckets

• Use approximately 1 ounce of dry ice for each gallon of container size.
• Wipe frost crystals from the dry ice using a clean towel.
• Place the dry ice in the center of the container bottom.
• Pour the food into the container to within ½ inch to 1 inch of the top.
• Place the lid on the container and snap it down only about halfway. This will allow carbon dioxide gas to escape from the partially sealed lid as the dry ice sublimates.
• Allow the dry ice to evaporate completely before sealing the container. To see if the ice has evaporated, feel the bottom of the container. If it is still very cold, the ice has not all evaporated.
• Watch the container for a few minutes after sealing the lid. If the container bulges, slightly lift the edge of the lid to relieve pressure.
• It is normal for the lid of the bucket to pull down slightly as a result of the partial vacuum created when the carbon dioxide is absorbed into the product.

Instructions for CO2 Gas Flushing for Dry-Pack Buckets

• Set up the gas flushing equipment using a cylinder, a pressure regulator, and a probe equipped with a pipe extension to reach the bottom of the bucket.
• With the probe valve open, adjust the regulator to the appropriate setting.
• Granular products (wheat, beans, etc.): 20 lb.
• Powdered products (milk, flour, etc.): approximately 3 lb.
• Fill the buckets to within ½ inch to 1 inch of the top.
• Gas flush product with carbon dioxide. Insert the probe to the bottom of the bucket. With the hand valve open, move the probe up and down in a circular motion for the appropriate length of time.
• Granular products—gas flush for 5 seconds.
• Powdered products—gas flush for 20 seconds.
• Seal the lid immediately on the bucket.
• Wipe off the probe with a dry towel when changing from one product to another to avoid cross-contamination of products.

Cautions

• Use CO2 in well-ventilated areas only.
• Wear gloves when handling dry ice.
• Dry-pack only products that are shelf stable. Products must be low in moisture and oil content.
• Avoid exposing products to humid, damp conditions when dry-packing.