As the gardens are in full swing, food safety educators at Penn State Extension will receive numerous calls and emails about fruit and vegetable conservation. With that in mind, now is a good time to share some of the most common questions we receive and our answers – it might answer a question or two that you might have!
When answering customer questions, we always use reliable scientific references. Unless otherwise noted, answers to questions in this article are based on information from the 2014 book, So Easy to Preserve, 6th edition by Elizabeth Andress, Ph.D. and Judy Harrison, Ph.D., Department of Food and Health nutrition from the University of Georgia.
1. How long can I keep green beans in a double boiler? The only safe way to store green beans is to use a pressure cooker. 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. Clostridium botulinum bacteria, a microorganism found in soil, can produce the deadly botulinum toxin under the right conditions. These conditions include a low acid, oxygen free environment and room temperature storage. These are conditions created when canning vegetables, meats, seafood, and other low-acid foods. To prevent this toxin from forming when canning low-acid foods, a temperature of 240 ° F must be reached for a period of time to destroy the C. botulinum spore. This temperature can only be reached using an autoclave. The water in a boiling water bath pot will never reach the boiling point; therefore, no matter how long the jars are in boiling water, the boiling water will not destroy C. botulinum spores. According to the Centers for Disease Control and Prevention website (2021), symptoms of botulism poisoning typically begin within 18 to 36 hours of consuming foods containing the toxin. Symptoms of botulism poisoning include difficulty swallowing, muscle weakness, double vision, blurred vision, slurred speech, difficulty breathing, and others. If left untreated, it can lead to death. Even if you’ve done a canned green bean water bath in the past and no one has ever gotten sick, it’s too risky! Always use a pressure cooker and follow research-based guidelines when canning low-acid foods; the life of you and your family depends on it!
2. Everyone loves my special barbecue sauce. I want to give it as a gift, how long do I have to process it in a boiling water bath pot? While you love to create recipes or have family recipes handed down from generation to generation, the only recipes you should use when canning are those that have been tested and approved by research. We have no way of knowing by looking at a recipe how long it needs to be processed in a water bath or autoclave to ensure that the correct time and temperature conditions have been met to destroy the microorganisms that can cause deterioration or disease. Martha Zepp, Penn State Extension Program Assistant, says in her May 2018 article Use Tested Recipes to Preserve Food, “There is no simple formula for determining turnaround times. Experimentation and analysis take into account how each food product heats up in a particular canning situation, and any variation that changes the pH, consistency, texture, distribution of solids and liquids, or d Other factors that result in a “new product” should be tested. Experimentally determining safe processing times for homemade canned foods is a long, expensive and time consuming process. Trusted sources of tested recipes include the 1994 or later edition of USDA’s Complete Guide to Home Canning, University of Georgia Cooperative Extension’s So Easy to Preserve, Penn’s Let’s Preserve Fact Sheets 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.
3. Should I blanch my vegetables before freezing them? For a quality product, blanching is an essential step in the freezing process. There are enzymes (chemicals) in vegetables (and fruits) whose activity slows down but does not stop during freezing. If not inactivated by blanching them in the case of vegetables or adding citric acid in the case of fruits, the enzymes will cause changes in color and flavor over time and loss of nutrients resulting in a poor quality product. Blanching also helps destroy surface microorganisms on vegetables. It makes the vegetables more compact, which makes it easier to pack them. It is important to follow the correct procedures related to the time it takes to blanch a particular vegetable, as over or under blanching can be worse than no blanching at all. For more information on blanching times, see the Penn State Extension fact sheet titled “Let’s Preserve: Freeze Veggies.”
4. My friend told me that she saw a video on the internet showing an easy way to can canning that won’t heat your kitchen. All you do is heat the food, put it in hot jars, put the lids on the jars, and wait for them to close. Can i do this? It seems so easy. This method is called “open kettle” or “hot fill” and is not recommended. Although the jar may seal, you have skipped the water bath or pressure canning process step. Processing by any of these methods is essential to ensure the safety of canned foods. During processing, the time and temperature necessary to destroy microorganisms is reached, enzymes are inactivated, and air is expelled from the jar to create a strong vacuum seal and airtight environment. A vacuum seal prevents other microorganisms from recontaminating the food in the jar and makes the product stable.
The bottom line is that food preservation is a science and as such has specific guidelines that must be followed to produce a safe, quality product. There is no shortcut!
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
Good food preservation!
Andress, E. & Harrison, J. (2014). So easy to preserve (6th ed.). Cooperative Extension, University of Georgia.
Centers for Disaster Control and Prevention. (2021, February 9). Botulism: Symptoms. Retrieved June 23, 2021, from https://www.cdc.gov/botulism/symptoms.html
Zepp, M. (2018, May 23). Use tested recipes for preserving foods. Retrieved June 23, 2021, from https://extension.psu.edu/use-tested-recipes-to-preserve-foods