A beginner’s guide to preserving the harvest

Posted Oct. 02, 2012, at 1:20 p.m.

Harvest season has peaked, and the bounty of berries, veggies and other produce is huge, and ready to be canned and preserved for the winter. To save some money and to retain the flavor of all that wonderful Maine-grown food — whether you or someone you know grew it — the folks at the University of Maine Cooperative Extension have lots of tips and tricks to make the most of your harvest. Here are some basics for first-time canners.

  1. There are two types of canning — water bath canning and pressure canning. Water-bath canning is for high-acidity foods, such as fruit and tomatoes, and for foods to which you’ll be adding acid, like jams and pickles. Pressure canning is for simple canning of foods such as corn, green beans, carrots or other vegetables, with no added acid. If there’s little or no acid present in the can, botulism spores can grow — and pressure canning heats the cans up high enough to kill those spores.
  2. Use clean Ball canning jars, with clean rings — you need to use a new lid every time. Jars, rings and lids all need to be sterilized before use. Food-safety experts also now recommend against using wax to seal lids, a procedure now considered less sanitary.
  3. Water-bath canning can be done simply, needing only a large stockpot, some clean jars and lids, and some jam or pickles. Plenty of other handy accessories are out there for canners to use, from tongs to lift jars out of hot water, to gauges to figure how much “head space,” or empty space just below the lid, is in your jar. Kits are available at most major retailers, from Walmart to Hannaford.
  4. Many brands of pectin are available for those making jam, though the two most common kinds are the ones that require sugar — 7 cups for one batch — and the ones that don’t require sugar. Using less sugar, no sugar or a sugar substitute can alter than consistency of the jam or jelly.
  5. Make sure at least 1 inch of water is above and below your jars while they are boiling in the pot. A glass jar can crack if it is too close to the heat source.
  6. Pressure canners can be purchased at Walmart and other retail locations. There’s a gauge on the front of your pressure canner that will tell you how much PSI — pressure — is being exerted on your jars or cans. These gauges should be checked once a year for accuracy, which can do for free at your local University of Maine Cooperative Extension office.
  7. If a recipe calls for 30 minutes of pressure cooking at 5 PSI, and at any point during the cooking the PSI falls below 5, the entire 30-minute cycle will need to be started again, to make sure all bad bacteria has been killed.
  8. Two excellent guides to canning are the University of Georgia’s “So Easy to Preserve” and the Ball “Blue Book Guide to Preserving,” both of which are available at UMaine Cooperative Extension offices. Extension offices also have a wealth of information available online at