Updated recommendations for safer canning

University of Maine Cooperative Extension is advising Mainers to get up-to-date information before canning their garden harvest. Botulism can occur when safe canning methods are not used, because botulism-producing bacteria thrive under the low-oxygen conditions found in canned foods, and at food pH levels above 4.6. Contact your UMaine Extension county office for current canning information.

Rising food costs have inspired many Mainers to plant new or expanded gardens this year with an eye to preserving their harvest. Yet many people may not know that vegetables that are not pickled (including pumpkin and squash) -- as well as meat, poultry, fish, and seafood -- must be canned using a pressure canner, because these foods have a low acid content. This is why canning salsa has been a hot topic this year: some tomatoes do not have enough acidity to make a safe canned salsa. The National Center for Home Food Preservation recommends adding two tablespoons of bottled lemon juice or a half teaspoon of citric acid per quart of whole, crushed or juiced tomatoes before water-bath canning.

Match the canner to the food

There are two types of home canning methods: boiling-water-bath canners and pressure canners. The type of canner that you use should be based upon the type of food you are preserving. According to UMaine Food Science Specialist Beth Calder, fruits, pickled foods, sauerkraut, marmalades, fruit spreads, jams, jellies, fruit butters (except for pumpkin) and salsa can be safely preserved using the water-bath canning method. “However, make sure you use a scientifically tested recipe from a reputable resource,” said Calder.

All other foods should be preserved using a pressure canner. This is because botulism-producing bacteria produce spores that can survive boiling water temperatures, but are destroyed using a pressure canner with the appropriate time and pressure, which reaches temperatures between 240 and 250 degrees F.

Dial-type pressure gauges should be checked annually for accuracy. Contact your UMaine Extension county office to determine whether they are equipped to test your dial gauge. If they are not, you can contact National Presto Industries, Inc. to have them test your dial gauge (this process can take up to two weeks). Call 800-368-2194, e-mail contact@gopresto.com, or write to Test Kitchen, National Presto Industries, Inc., 3925 North Hastings Way, Eau Claire, Wisconsin 54703-3703.

Use the right types of jars and seals

Only glass mason-type jars with self-sealing lids and screw bands should be used. Avoid older glass canning jars with the wire bales and rubber rings. Also, the use of paraffin wax in jam or jelly products does not ensure a proper seal and is no longer recommended.

Resources for home canning

UMaine Extension publishes the Let’s Preserve series of 13 publications on home canning, and also offers So Easy to Preserve from University of Georgia Cooperative Extension. Call (207) 581-3892 or visit www.extension.umaine.edu and choose Publications, Food & Health, Food Safety. Also the Ball Blue Book Guide to Preserving can be found through many online booksellers as well as at stores that sell canning supplies. The National Center for Home Food Preservation carries the USDA’s Complete Guide to Home Canning as well as a wealth of information and recipes; visit www.uga.edu/nchfp.

The Maine Department of Agriculture would like to remind consumers that canned low-acid vegetables cannot be processed for selling. Call (207) 287-3841 if you have questions on this topic.