By Leslie Shallcross
As summer harvesting peaked in August and September, food preservation questions kept my Extension phone lines busy. Calls frequently start with, “How long should I process this in the pressure canner?” or “My family always does it this way.”
Even if the individual isn’t asking whether their product is safe, safety is my first priority and I will ask quite a few questions to fully understand the methods used — from the type of canner to the exact contents of the jar and source of the instructions.
I have always taken this approach after one of my very first canning classes provided a lesson that I have carried with me for the past 17 years. Each student introduced themself and described their experiences with food preservation, mostly expressing considerable confidence, since their families had been canning food “forever.” One student, though, also describing generations of family food preservation, shared the sad detail that a close relative had died from eating home-jarred food!
Since then, I have never been afraid to emphasize that home canners must follow tested methods and recipes, even if this means giving up the old family traditions.
Clostridium botulinum is a potentially fatal microorganism that can produce toxins in insufficiently heated, low-acid canned foods. The toxin causes neurological damage and even if it is not fatal, there can be long-lasting, unpleasant effects (just ask someone who has experienced it).
Getting the food hot enough for long enough in the pressure canner and using laboratory-tested recipes and methods will ensure that your jarred products do not contain botulism. Following each researched step in the jarring process is important for safety. Here is some guidance for canning or jarring a safe product:
• Do not make up your own recipe. The exact amount and combination of ingredients affect how long a product needs to be heated and whether you need to use a pressure canner or a boiling water bath canner. This can only be determined through laboratory testing.
• Do not add starch, flour or thickeners to products before canning. Changing the thickness of the product will change the heat penetration through the contents and may make the product unsafe.
• Do not add extra low-acid ingredients like onions, peppers or other vegetables to a salsa or sauce. This could reduce the amount of acid in the product and botulism poisoning could result.
• Do not shorten the warming up or cooling down time in the pressure canner. All of the processing time is important for complete heat transfer through the product and destruction of the botulism spores.
• Do not forget to “exhaust” your pressure canner. Allowing a thick plume of steam to escape for 10 minutes prior to closing the vent or the petcock assures that you do not have uneven heat in your canner.
• Do not forget to adjust pounds of pressure (psi) or time if you are canning at a higher altitude. At a higher altitude, water boils at a lower temperature, so you may not be getting your product hot enough. Follow adjustments for altitude recommended in USDA publications.
• Do not allow a “hot packed” food to cool before putting it in the canner or you could risk under-processing.
• Do not use vinegar with less than 5% acidity. The safety of recipes is based on this amount of acid — less acid could allow clostridium botulinum to produce its dangerous toxin.
A quick Alaska note — for many years, people processed pints and half-pints of salmon in a pressure canner for 90 minutes (at 10 pounds of pressure with a weighted gauge or 11 pounds of pressure with a dial gauge). However, more recent research determined that 100 minutes is required to destroy the dangerous spores of Clostridium botulinum in pints or half-pints of jarred fish (110 minutes for smoked fish).
For many, canning is a family tradition allowing the storage of seasonally available food like moose, salmon, potatoes, carrots and berries without taking up freezer space. The jarred contents make for quick and easy meals and are often better tasting and more nutritious than comparable commercially canned products.
Please keep canning and make it safe by following current researched methods from Cooperative Extension and the USDA. For more information about food preservation, call Leslie Shallcross at 907-474-2426.
Leslie Shallcross is a registered dietitian and the Tanana District health, home and family development agent for Cooperative Extension Service, a part of the University of Alaska Fairbanks, working in cooperation with the U.S. Department of Agriculture. She can be reached at 907-474-2426 or lashallcross@alaska.edu.
