The principles behind safely preserving food at home
Find out how the different methods of food preservation keep your food safe.
The most common method of preserving food is canning. This process was developed about 150 years ago. The goal of food preservation is to increase the shelf-life of food while keeping it safe to eat. Not all foods can be safely preserved at home since the required equipment and ingredients are not always available to the consumer.
For consumers to safely preserve foods at home, researched-based methods such as the United States Department of Agriculture Complete Guide to Home Canning must be followed. Other such resources include “So Easy to Preserve” from The University of Georgia Cooperative Extension. Michigan State University Extension also provides face-to-face workshops and an online home food preservation course.
Preserving using a canning method involves placing food in specified canning jars that are sealed with two-piece lids. The jars are heated to a temperature that destroys harmful microorganisms and inactivates enzymes. This heating, and later cooling, forms a vacuum seal. This vacuum seal prevents further microorganisms from entering the jar and contaminating the foods during storage.
Pickling is another form of canning. The addition of vinegar to this method makes the food so acidic (pH less than 4.6) that harmful bacteria cannot survive or grow. The pickling method includes heating the jars in boiling water at 212 degrees F which will destroy microorganisms and form a vacuum seal in the jar to prevent contamination during storage.
Jelly and Jam
Jelly and jam making is another form of canning. The high sugar content binds with the water present, making microbial growth difficult. To prevent surface contamination after the food is made, such as yeast or mold growth, jellies and jams are sealed through either heat processing, freezing or refrigeration.
Drying is a form of preservation through the removal of moisture from foods. This inhibits the growth of microorganisms. Dried foods should be stored in airtight containers to prevent moisture that would allow microbial growth.
Freezing is one of the simplest methods of preserving. Freezing foods at zero degrees F or below slows the growth of microorganisms and enzyme activity. Blanching of most vegetables inactivates the enzymes that lead to spoilage.
Whichever method you select to preserve foods at home, remember to use researched-based recipes and follow the manufacturer’s directions on canning equipment. MSU Extension is a great source for questions or concerns when preserving foods at home.