Four frequently asked home food preservation questions
With gardens in full swing, Penn State Extension food safety educators will be receiving many more calls and emails about preserving fruits and vegetables. With that in mind, this is a good time to share some of the most common questions we receive and our responses — maybe it will answer a question or two you may have!
When responding to client questions, we always use reliable, science-based references. Unless otherwise noted, responses to the questions in this article are based on information from the 2014 book, “So Easy to Preserve, 6th edition” by Elizabeth Andress, PhD and Judy Harrison, PhD, University of Georgia Department of Foods and Nutrition.
How long do I can green beans in a water bath canner?
The only safe way to can green beans is to use a pressure canner. Green beans, other vegetables, meats, and seafood are low acid foods with a pH of 4.6 or higher. When these foods are canned, an anaerobic or oxygen free environment is created. The bacteria Clostridium botulinum, a microorganism found in the soil, can produce the deadly botulism toxin under the right conditions. These conditions include an environment low in acid, free of oxygen, and storage at room temperature. These are conditions created when canning vegetables, meats, seafood, and other low acid foods.
To prevent the formation of this toxin when canning low acid foods, a temperature of 240∂F must be reached for a specific amount of time to destroy the C. botulinum spore. This temperature can only be reached by using a pressure canner. Water in a boiling water bath canner will only ever reach the boiling point; therefore, no matter how long the jars are in the boiling water, the boiling water will not destroy the C. botulinum spores.
According to the Centers for Disease Control and Prevention website (2021), symptoms of botulism poisoning generally begin within 18 to 36 hours after eating food containing the toxin.
Symptoms of botulism poisoning include difficulty swallowing, muscle weakness, double vision, blurry vision, slurred speech, difficulty breathing, and others. If not treated, it can result in death.
Even if you water bath canned green beans in the past and no one ever got sick, it is too risky! Always use a pressure canner and follow research-based guidelines when canning low acid food; you and your family’s life depends on it!
Everyone loves my special barbecue sauce. I want to can some to give as gifts, how long should I process it in a boiling water bath canner?
While you may love creating recipes or have family recipes handed down through the generations, the only recipes you should use when canning are those that have been research tested and approved.
We have no way of knowing by looking at a recipe how long it must be processed in either a water bath or pressure canner to ensure that the right time and temperature conditions have been met to destroy microorganisms that can cause spoilage or illness.
Martha Zepp, Penn State Extension Program Assistant, states in her May 2018 article Use Tested Recipes to Preserve Food, “There is no easy formula to determine processing times. Experimentation and analysis take into account how each food product heats in a particular canning situation, and any variation that changes the pH, consistency, texture, distribution of solids and liquids, or other factors that result in a ‘new product’ must be tested. Experimentally determining safe processing times for home canned food is a lengthy, expensive and time-consuming process.”
Reliable sources of tested recipes include the 1994 or later edition of the USDA’s “Complete Guide to Home Canning, So Easy to Preserve” from the University of Georgia Cooperative Extension, “Let’s Preserve” fact sheets from Penn State Extension, or information from other Cooperative Extension Services. Therefore, for that special barbecue sauce, salsa, or secret family recipe, the best and safest option is to freeze it.
Do I have to blanch my vegetables before I freeze them?
For a high-quality product, blanching is an essential step in the freezing process. There are enzymes (chemicals) in vegetables (and fruit) whose activity slows down but does not stop during freezing. If not inactivated by blanching in the case of vegetables or by adding citric acid in the case of fruit, the enzymes will cause color and flavor changes over time and loss of nutrients resulting in a poor-quality product.
Blanching also helps to destroy surface microorganisms on vegetables. It makes the vegetables more compact, making for easier packaging.
It is important to follow correct procedures related to amount of time to blanch a particular vegetable, as over or under blanching may be worse than no blanching at all. For information on blanching times, check Penn State Extension’s fact sheet titled “Let’s Preserve: Freezing Vegetables.”
My friend told me she saw a video on the internet showing an easy way to can that will not heat up your kitchen. All you do is heat the food, put it into hot jars, put the lids on the jars, and wait for them to seal. Can I do this?
It sounds so easy. This method is called “open kettle” or “hot-fill” canning and is not recommended. While the jar may seal, you have skipped the processing step of water bath or pressure canning. Processing by one of these methods is critical to ensure a safe canned food.
During the processing, the time and temperature needed to destroy microorganisms are reached, enzymes are inactivated, and air is driven out of the jar to create a strong vacuum seal and an airtight environment. A vacuum seal prevents other microorganisms from recontaminating the food in the jar and makes the product shelf stable.
The bottom line is food preservation is a science, and as such has specific guidelines that must be followed to produce a safe, quality product. There are no shortcuts!
If you are looking for reliable resources, contact your local Extension office or visit our website at https://extension.psu.edu/food-safety-and-quality/home-food-safety
Happy food preserving!
Laurie Welch is a nutrition and family issues educator with Penn State Cooperative Extension, 570-726-0022.