The water we drink, the air we breathe and the soil in which some foods grow all contain microorganisms. They are a naturally occurring part of the life cycle. Even though we can’t see microorganisms with our eyes, it is still very important to control microorganism growth which allows food to spoil and deteriorate.
One way to control food spoilage is to expose the microorganisms in food to heat and hermetically seal the heated food. Heat kills microorganisms and inactivates enzymes in food to prevent further deterioration. Hermetic means completely airtight, so no air can get back in the jar to re-contaminate it. This is the process we call home canning. There is a delicate balance between acidity or pH, temperature and time when processing foods.
The acidity of the food being preserved determines the heat processing method— boiling water or pressure canner. The acidity or the pH of a food is used to divide food into two groups: high and low acid foods. Each group requires a particular heat processing method. Acidity is determined by the level of acid naturally present in a food or added to a recipe or mixture. For example, 5% vinegar or bottled lemon juice may be added to some borderline or low-acid foods such as pickling vegetables.
Foods or recipes that have a pH of 4.6 or lower are considered high-acid foods. These foods may be safely heatprocessed in boiling water. A boiling water canner heats food to 212 degrees Fahrenheit, which is hot enough to kill molds, yeasts and other bacteria found in high-acid foods. Some high-acid foods include fruits, jams, jellies and other fruit spreads. However, some foods such as figs and tomatoes are on the borderline between high and low acid and require the addition of an acidic ingredient such as 5% vinegar or lemon juice to be safely processed in a boiling water canner. There are other pickle and relish recipes that contain both high and low acid foods but are high enough in acidic ingredients that they reach a pH of 4.6 or lower.
Low-acid foods have very little natural acid. This group includes vegetables (unless pickled) and meats. This group also encompasses soups, stews, tomato-veggie mixes, and other meat sauces. All foods in this group must be heat processed in a pressure canner, which heats food to 240 degrees Fahrenheit for the specific amount of time and pressure in the recipe. This is the temperature required to destroy toxinproducing bacterial spores.
It is very important never to alter a canning recipe because you might change the pH of the recipe and make someone very sick or worse. It is also important to use recipes that are current within the last five years. New findings and new varieties of fruits and veggies are always a possibility, and it is best to be up to date for safety’s sake.
Be sure and get your pressure canner a free check for the correct pressure at the Sequoyah County Extension office.
I also want to remind you to attend your Farmer’s Markets or roadside vegetable stands in parts of our county for the freshest fruits and vegetables. Check them out on Facebook and on their website. It is a great place to get local fresh foods and products from some really great people!
For more info about financial management, nutrition, health & wellness, parenting education or to schedule a program with the Family and Consumer Sciences Educator, contact Janis Risley, at the OSU Cooperative Extension Service in Sequoyah County at 918-775-4838 or janis. risley@okstate.edu.
