Food Safety: Don’t be influenced; there are hazards todry canning

Although social media can generate new ideas, tips and tricks, it can also be a source of very dangerous information. Online misinformation on the dry canning of foods such as grains, legumes and vegetables poses a threat. Safe canning is a science, not an art form, and not following recipes that have been well researched for safety can be deadly.

Dry canning vegetables involves placing them in canning jars with no added liquid, placing lids and pressure canning for various times. USDA, the National Center for Home Food Preservation (NCHFP), and university extension canning recipes always require the addition of a liquid to ensure proper heat penetration to destroy the pathogen Clostridium botulinum, the organism responsible for causing botulism. Only by adding the proper amount of liquid to a jar and pressure canning using a well-researched process, such as those available through the USDA or your local extension office, can C. botulinum and its spores be destroyed. If this pathogen is not destroyed during the canning process, there is a risk that C. botulinum will produce botulinum toxin in the food, and consumption of this toxin can be deadly or result in severe, lifelong health issues. C. botulinum can be present in canned food without showing any signs of discoloration or odors.

Dry canning grains and beans involves a similar process to that of vegetables. These foods are placed into a canning jar without liquid and processed in a pressure canner, water bath canner, or oven. Many believe this allows for more extended storage of these dried grains. However, processing grains and beans in this manner can cause trace amounts of water to be pulled out of the interior of these foods, or the canning process itself may allow for condensation to form within the jar. This small amount of water can allow growth and subsequent toxin production by C. botulinum. Additionally, the heating process is insufficient to kill this microorganism. Dried foods may be stored in canning jars but should never undergo heat processing. USDA recipes, which have been researched for safety, require that dried beans and peas are rehydrated prior to canning using one of the following steps:

1. Place sorted dried beans in a large pot and cover with water, then soak for 12 to 18 hours in a cool place before draining and proceeding with canning instructions or;

2. Cover the sorted and washed beans with boiling water in a saucepan, boil for 2 minutes, remove from heat, then soak for 1 hour before draining.

Note: Never use cooking or soaking water for the canning process.

After following one of these processes, beans are covered with fresh water and boiled for 30 minutes, then quickly filled into jars and processed. Make sure the water fully covers them to ensure even heat distribution throughout. Never take shortcuts and always use recipes and processing times provided by USDA, the NCHFP, or extension.

Foods made with grains, such as flour or pasta or those containing rice, should never be added to canned foods prior to the canning process unless the recipe specifically states that it is OK to do so. Adding these products to foods before canning will alter the viscosity, which also affects heat penetration. This is likely to result in food that has been under processed and may still harbor C. botulinum, making it unsafe to eat. Most recipes will call for the grains to be added when reheating the food for consumption.

For more information on canning beans, peas and vegetables, please visit WSU Extension at extension.wsu.edu/foodsafety/food-processing or the NCHFP at nchfp.uga.edu.

Smith is an assistant professor and statewide consumer food specialist for Washington State University. She can be reached at food.safety@wsu.edu. If you have a food safety question you would like to see in this column, send your question to us at food.safety@wsu.edu