Food Safety FAQs

Home canning is an excellent way to preserve garden produce and share it with family and friends, but it can be risky—or even deadly—if not done correctly and safely. Whether you are an experienced canner who has preserved food for years or a novice wanting to learn more about home canning, the key to canning is safety.

Q: Why is cleanliness stressed when preserving food?
A: Clean hands, utensils and surfaces are critical in preparing safe food. As food moves through your kitchen, unsafe food handling practices can lead to the unintentional spread of bacteria that could cause foodborne illness.

Q: How do I know if the canning method I am using is safe?
A: Home canning can be a fun, inexpensive and convenient way to store food for future use. However, canned food can be safe or unsafe depending on how it is preserved. Preserve your food safely by using research-based preserving methods.

Q: I have heard it may be unsafe to use old family canning recipes – why is that?
A: Many recommendations for canning methods have changed over the past years. Canners need to update their methods to keep food – and people – safe. If you have not updated your canning recipes or methods in a few years, now is a good time to take a look at them.

Q: Why can’t I reuse commercial jars for canning?
A: Specific equipment is needed to preserve food at home safely. Some of the most important supplies are proper canning jars. The canning process requires the heating and cooling of food to form a vacuum seal. When food is packed into canning jars, the headspace is filled with air. During processing, air is pushed out of the jars and the headspace fills with steam. When processing is completed and the jars cool, the contents shrink. A vacuum forms within the jar and pressure holds down the lid. The sealing compound on the lid prevents air from re-entering the jar, as well as microorganisms that could contaminate the food. Specific glass canning and freezing jars are recommended because glass does not react with its contents. preservationsafety. 

Q: I have an abundance of over-ripe produce – are there any drawbacks to canning these?
A: The quality and safety of home-preserved foods is dependent, in large part, on the ingredients that are used. Selecting the highest quality fruits and vegetables at their peak of freshness is the first step. Those that show signs of decay or are heavily bruised should be avoided.

Q: What are unsafe canning methods that I should be aware of?
A: Solar canning, oven canning, open kettle canning, microwave processing, and dishwashing processing are not safe canning methods.

Q: How do I adjust canning times when I live in a high altitude region?
A: If you live at a high altitude, safely canning foods at home means you must adjust standard recipes based on your location. Altitude affects the processing times for water bath canning and the pressure requirements for pressure canning. Don’t let these factors intimidate you or discourage you from preserving at home: Whether you’re a novice or a pro, it’s easy to convert recipes based on your elevation.

Q: Why is it necessary to acidify tomatoes?
A: Tomatoes are one of the most commonly canned vegetables. Canning procedures for tomatoes have been handed down from generation to generation. Unfortunately, there are many canning recipes that are inadequate to kill all spoilage microorganisms. Canning recommendations for tomatoes have changed over the years so be sure you follow the most up to date guidelines when canning tomatoes.

Q: I have been told I cannot can vegetables in a water bath canner due to safety concerns – why is that?
A: Whether food should be processed in a pressure canner or boiling-water canner to control botulinum bacteria depends on the acidity of the food. Acidity may be natural, as in most fruits, or added, as in pickled food. Low-acid canned foods are not acidic enough to prevent the growth of these bacteria.

Q: Why are temperatures important in food preservation?
A: Keeping food at a proper temperature is one of the most important things a food handler can do to prevent bacteria that cause foodborne illness from growing rapidly. Leaving certain foods out for a long time in certain temperatures creates conditions for bacteria to grow, sometimes to dangerous levels. 

Q: I have decades old canning recipes from family members – are they safe to use?
A: While it’s a wonderful, cherished tradition in many families to preserve food based on recipes that were developed and kept over many years, you should review those recipes, and if they don’t match recipes that have been tested and researched by food safety experts, you shouldn’t use them.