Home food preservation is an ancient art that needs to be based on current science to keep you and your family safe. It is possible that the methods used by grandpa, mom, or even the way you’ve ‘always done it’ may not be based on the safest, most up-to-date guidelines.
As a human sciences specialist in food and health with Iowa State University Extension and Outreach, I recommend following procedures and recipes from the National Center for Home Food Preservation (https://nchfp.uga.edu/#gsc.tab=0) or resources from ISU Extension and Outreach. These sources have reliable research processes in place to ensure all the recipes are safe. The jar size, food type and density, altitude and type of canner are all part of the rigorous research, and guidelines are being updated continuously as we learn new scientific information.
One example is white-fleshed peaches. Newer research showed that unlike other fruits, they are not very acidic. There are no canning recommendations for them, even in a pressure canner. White flesh peaches should instead be frozen to preserve them.
A few tips, based on questions from consumers:
• Water bath canning, steam canning and pressure canning are the only safe ways to can at home. The type of canning you do is based on the acidity of the food. Water bath and steam canning are for high acid foods such as fruits, fermented foods such as sauerkraut, or foods like pickles or salsa, where a large amount of acid has been added. Pressure canning is the only safe way to can low acid foods such as vegetables or meat.
• Dry canning (no added liquid in the jar) and oven canning are not safe home canning processes.
• Home canned salsa requires a tested recipe from a reliable source to ensure it is safe. If your family favorite salsa is not from a tested source, you can make it and freeze it.
• Know the altitude of the location where you are canning and how to adjust. Water boils at a lower temperature at altitudes over 1000 feet above sea level. An altitude map of Iowa can be found on all ISU Extension and Outreach food preservation publications. Here is one example: https://store.extension.iastate.edu/product/4369. Much of Iowa has altitudes between 1001–2000 feet above sea level, requiring altitude adjustment when canning.
• Always acidify tomatoes when canning them. Bottled lemon juice or citric acid are the preferred acids to use. Tomatoes are not consistently acidic enough without this, even though they seem like an acidic food. See the ISU Extension publication on Canning and Freezing Tomatoes: https://store.extension.iastate.edu/product/3990.
• Do your homework and learn how to safely preserve food before you jump into the process. Research shows most problems with home food preservation are due to user errors.
Freezing and drying are not as risky, food safety-wise, but the quality and shelf life of foods using these methods will be best if using up-to date recommendations.
ISU Extension and Outreach is offering free, interactive, online food preservation trainings yet this year
(https://www.extension.iastate.edu/humansciences/preserve-taste-summer#workshops):
• Salsa Making Basics – August 11 or September 12
• Totally Tomatoes – August 22
• All About Apples – September 27 or October 12
Hands-on workshops on making salsa, pickles, jams, and pressure canning are also available. Check with your local county ISU Extension and Outreach office for more details on these.
One more reminder – AnswerLine is a free call to Iowa residents. They provide expert advice on all things related to home and family, including food preservation questions.
• Email: answer@iastate.edu
• Phone: (Monday-Friday, 9 am-noon; 1-4 pm): 1-800-262-3804 (in Iowa) or 1-800-854-1678 (in Minnesota)