Canners and canning methods to avoid

by Angela Treadaway

Steam Canners - The steam canner was designed as a means to process foods using steam without the aid of pressure. The manufacturer claims this process uses less water, saves time and energy, and recommends identical processing times as those required for boiling-water bath treatments.

Studies have concluded:

1. Atmospheric steam canners result in significantly lower product temperatures at the beginning and end of the scheduled process when compared to water-bath canning.

2. Use of steam canners as instructed by the manufacturer would result in under processing and considerable economic spoilage.

Micro-Dome Food Preserver - Micro-Dome Food Preserver Recalled Washington, DC – The U.S. Consumer Product Safety Commission (CPSC) in cooperation with Micro-Dome of San Ramon, CA, has warned consumers of certain safety hazards associated with the use of the "Micro-Dome Food Preserver" manufactured by Micro-Dome and sold and distributed to consumers after August 1987. The CPSC has also urged consumers to destroy all food preserved using a Micro-Dome Food Preserver.

Solar Canning - The heat generated from captured sunlight is not a reliable method to process acid foods and should never be used to can low-acid foods.

Oven Canning - Oven canning is extremely hazardous. The oven-canning method involves placing jars in an oven and heating. In oven canning, product temperatures never exceed the boiling point because the jars are not covered. It is, therefore, not safe to use for low-acid products (e.g. meats, most vegetables) which require temperatures higher than 212° F.

Because this process fails to destroy the spores of Clostridium botulinum, it can cause the food to become toxic during storage. Also, canning jars are not designed for intense dry heat and may explode resulting in serious cuts or burns.

Open Kettle Canning - The open-kettle method involves placing hot food in jars and sealing with no further heat treatment. This method is NOT recommended for home canning because the amount of heat applied may not be sufficient to destroy bacteria and the product may spoil quickly or cause illness when consumed.

Microwave Processing - Microwave ovens cannot be used for home canning. Microwaved food reaches 212° F, but heating is not uniform. There is also a danger of explosion of the jars within the microwave oven or as food is being removed from the oven.

Dishwashing Processing - Processing canned foods in a dishwater cycle is dangerous. The temperature of the water during the cleaning and rinsing cycle is far below that required to kill harmful microorganisms. Thus the product will be underprocessed and unsafe to eat.

Dial Gauge and Weighted Gauge Canners - The safest types to use are preferably ones less than 20-25 years old because of the safety features added like locks in the handles. Also remember, if you have a dial gauge pressure canner, you need to have it checked once a year before canning season starts and you can contact your local county Extension office to have that done. Weighted or giggler-gauge pressure canners do not need to be checked except for changing the gasket when it no longer seals properly.

Be sure to contact your local Extension office or Regional Extension Agent Angela Treadaway for the most up-to-date information on the correct type of equipment to use for canning those fruits and vegetables.

Angela Treadaway is a Regional Extension Agent in Food Safety. For any questions on food safety or preparation of vegetables, contact her at (205) 410-3696 or your local county Extension office.