Canning mistakes to avoid: Part 1

Preventing these mistakes can save you time, money and your life.

Summer may be dwindling, but canning season is still in full swing. Canning, and other forms of food preservation, aim to stave off the growth of spoilage organisms and dangerous bacteria so that fruits, vegetables and meats can be enjoyed all year long. While not a terribly difficult process, canning is a science and there are some very important steps required in order to make sure the food is safe. The following are common mistakes made before you even get into processing your food, and tips on how to prevent them:

Using outdated/unsafe methods

Canning in ovens, microwaves or dishwashers - there are even a few books out there that talk about canning in compost piles - none of these methods are considered safe. There are three safe methods- boiling water bath, pressure canning and steam canning, depending on the product you’re preserving.

Using boiling water method when pressure canning is required

Determining which method is needed depends on the acidity of the food. Foods high in acid (fruits) can generally be safely processed in a hot water bath or steam canner. Low acid foods (vegetables and meats) must be pressure canned in order to be safe. Tomato products fall on both sides of the acid scale, so it’s important to follow an approved recipe for the product you are processing.

Using outdated or unapproved recipes

Grandma’s pie filling recipe might be what you know and love, but did you know that many aspects of the science of canning are updated regularly, making grandma’s recipe potentially dangerous? Changes like the processing time might seem insignificant, but can mean the difference between spoiled food and safe food. Use recipes from reputable publishers, and make sure the publishing date is no more than 5-6 years ago. You also never want to make up, or alter recipes. Remember acidity, or pH? The acidity of food for canning is one of THE most important considerations and unless you own a lab-grade pH meter (which cost thousands of dollars) there is no way to know the pH of the food you’re preserving. So, you’re homemade salsa recipe might taste great, but canning it could be unsafe. The same goes for recipes on the general world wide web-there are lots of people creating recipes that taste great, but haven’t been tested for safety. Approved canning recipes can be obtained from the USDA, and the National Center for Home Food Preservation.

Using improper equipment

Re-using spaghetti sauce jars from the supermarket is not a safe practice as they were made for a specific process, and the lids were only meant to seal once. Many jars from other products are also not standard sizes, and therefore the processing time for safety would be unknown. Also, canning in pots that were not designed for canning can lead to problems. These issues are related to physics. For example, canning in a pot much smaller than a standard canner may result in the water heating up more quickly, thus cutting down the total processing time, leaving your product “undercooked.” Lastly, “pressure cookers” cannot be used for “pressure canning.”

Using inferior ingredients

So your friend gave you three bushels of apples they picked up off the ground and you want to make applesauce. Using products picked off the ground, overripe fruits or vegetables, or otherwise inferior products could lead to food spoilage. Bacteria could be picked up from the ground and transferred to your jars, and produce with blemishes or soft spots can also harbor bacteria. Use only high quality, fresh produce that has been washed and stored properly.

Avoiding these common mistakes will help ensure that your preserved food will be safe to eat all year long. Part 2 of this series will look at mistakes that happen during processing. For more information on canning, or to take a class, contact your local Michigan State University Extension office.

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