Fight Bacteria when Preserving Food

Cleanliness and temperature control are essential for food safety.

Clean

Keep hands, counters, equipment, and food clean. Wash your hands often before and during the process of canning. You touch many things while canning—raw food, your hair, pets, dirty counters and used utensils, raw meat, and other foods being prepared for family meals—wash your hands each time you touch one of these potential carriers of bacteria.

Wash cutting boards, dishes, utensils, jars, and countertops with hot soapy water before and after preparing each food item. Use plastic or other non-porous cutting boards that can be washed in the dishwasher or hot soapy water after use. If you have any cuts on your hands, wear plastic gloves.

Clean counters with soap and water to remove dirt, crumbs, and microorganisms; then wipe with a sanitizing solution. Paper towels are ideal for wiping kitchen surfaces. Dish cloths and towels need to be cleaned and laundered in hot water frequently.

Separate

Do not cross-contaminate. That's a scientific word for how bacteria can be spread from one food product to another. Use a clean cutting board and utensils to slice or cut foods. Avoid using the same cutting board or knife to slice vegetables as you use to cut meat.  Clean knives after each use. Use clean spoons to stir the product. Don't use the spoon that you used to stir the product to stir the almost finished food. Use paper towels to clean up kitchen surfaces and wipe the edges of jars before applying lids—those fabric dishcloths and sponges hold bacteria that can be transferred from one place to another.  Use a clean bowl or pot to hold peeled food. Never place clean food or cooked food on or in a container that previously held unwashed food.

Control Temperature

Bacteria grow best between 40°F and 140°F, the temperature danger zone. Keep perishable produce refrigerated until you are ready to can. Once you start the canning process, continue until finished. Work with one canner load at a time so that peeled food is not in the danger zone for more than two hours. A large volume of food cools slowly, meaning that it is in the danger zone long enough to spoil. Allowing tomato juice or vegetable soup to sit in a five-gallon container at room temperature overnight is inviting disaster. Even a one-gallon container that is refrigerated can spoil quickly. Do not partially prepare food ahead of time to can or freeze later.

Chill

If you do have a large portion of food that must be refrigerated, chill it in an ice water bath stirring until the temperature drops below 70°F and then divide into smaller containers, not over three inches deep. Refrigerate these smaller containers below 40°F until ready to use or freeze. Use a thermometer to check the temperature. Never cluster large jars or other containers in a refrigerator, not even in a walk-in refrigerator. Allow air space between containers in the refrigerator for the food to cool. A normal size home refrigerator is limited in the amount of food it can safely cool at one time.

Choose an Appropriate Preservation Method

Use the correct canning method based on the food you are preserving. Select pressure canning for low acid foods and water bath canning for high acid foods. Follow research-tested recipes for safe processing times and temperatures. Following these guidelines will result in a safe and delicious product.

Foods that are not safe to can or which do not have a research-tested procedure for canning are often suitable for freezing. See Penn State Extension's Let's Preserve: Freezing Vegetables and Let's Preserve: Freezing Fruit for further instructions. For example, pumpkin puree cannot be canned, but freezes well.  Freezing temperatures will control bacterial growth. There may be quality issues with freezing foods having a high water content, but it will not be a safety issue.

Drying food is another alternative if adequate water is removed to prevent bacterial activity.

Following these guidelines will result in a safe and delicious product.

References:

1. National Institute of Health. (2020, September 23). "Cleaning, Disinfecting, and Sanitizing." Medicine Plus.
2. Partnership for Food Safety Education. (2023). Retrieved 2023, March 31. "The Core Four Practices". 
3. Zepp, M., Hirneisen, A., & LaBorde, L.; (2019, March 13). "Let's Preserve: Drying Fruits and Vegetables (Dehydration)". Penn State University. 
4. Zepp, M., Hirneisen, A., & LaBorde, L.; (2018, December 18). "Let's Preserve: Freezing Fruits". Penn State University. 
5. Zepp, M., Hirneisen, A., & LaBorde, L.; (2019, March 21). "Let's Preserve: Freezing Vegetables".  Penn State University.