As the taste of freshly grown local produce is almost impossible to beat and recycling efforts coming to the forefront, the science of canning and preserving is now being tested by a new generation with vast numbers of Americans planning to prepare and preserve sauces, preserves, and even pickles made from locally grown produce and enjoy them all winter long.
Studies show the produce you buy at the supermarket is shipped an average of 1500 miles before it ends up on the shelf and with little old-fashioned ingenuity and a few free hours to kill, most anyone can learn to can. Most food preservationists will tell you that it is fun, easy, nutritional, and it saves money.
Home canning is considered to be an art, but it is by no means a mysterious practice, said Tracy Buckles, Family and Consumer Science/4-H Extension Agent with the Johnson County Extension Office. Successful home canning requires only that you observe simple guidelines.
The reasons for preserving food these days are different from years past. More and more people are turning to backyard gardening in an effort to save money and to get that fresh-picked flavor and nutrition, minus commercial fertilizers and pesticides, which sometimes lead to food recalls.
The University of Tennessees Institute of Agriculture offers an online publication – Canning Foods, Fruits Vegetables Pickles Jellies. In this extensive manual, which includes graphics and recipes, Janie L. Burney, Professor, Family and Consumer Sciences, explains the importance of proper preservation. Food is preserved by using methods that destroy or hinder the growth of microorganisms, such as molds, yeast and bacteria, she writes. These organisms may be present in the soil, on the food, in the air, on equipment or on work surfaces. Yeasts, molds and bacteria must be destroyed during processing to prevent the food from spoiling. The correct amount of time to process varies with the kind of food.
Sufficient heat for a specified length of time kills microorganisms and insures a safe product. Higher temperatures are required to destroy botulism bacteria in low-acid food like meats, fish, poultry and all vegetables, EXCEPT tomatoes, explains Buckles. The only safe way to can these foods is by using a pressure canner so that you reach a temperature of 240 degrees, which is higher than that of boiling water at 212 degrees.
Processing also helps to secure an airtight seal when using closures containing sealing compound. Preventing enzymatic changes in food is another concern when preserving food. Enzymes, which aid in the maturing and ripening processes, are chemical substances found in all animals and plants, which can cause problems with flavor, texture or safety of the food being preserved if not destroyed.
Buckles cautions using any can in which the seal is not airtight. If bacteria and yeast are growing, they can produce gas that causes seals to break or lids to bulge, she said. Before you open a jar, examine the seal carefully. It should be tight and the center should be concave. Hold the jar at eyelevel, turn it and examine the outside for streaks of food coming from the top. Look for rising air bubbles and unusual color. Open the jar, look for mold under the lid and on top of the food. It may be blue, black, white or green. If you open a jar that has not sealed properly or see any signs of spoilage, NEVER TASTE THE FOOD. She advises to dispose of spoiled foods properly and wash your hands well.
While there are several ways of preserving food: hot water bath canning, pressure-cooking, dehydrating and freezing, the safest method of canning food is pressure canning. Buckles explains the difference between pressure canners – the kind with a dial versus the one with a weight control. Both are accurate if used and cared for according to the manufacturers instructions, she said. Some people prefer to read numbers on a dial; others like the sight and sound, such as the jiggling noise, of the weighted gauge. Dial gauges should be checked each year before canning to be sure they are measuring pressure accurately. Call your local Extension office to arrange a time to have your dial gauge checked. This is done free of charge by the Family and Consumers Science agent. You only need to bring the lid, not the entire canner, to the office for it to be checked to make sure the gauge is calibrated correctly, said Buckles.
Some general guidelines are provided by the United States Department of Agriculture. To use the USDA recommended canning procedures, make certain to select a pressure canner/cooker that is capable of holding at least 4 quart size jars, on the rack, with the lid in place ready to can. Also make sure all parts of the pressure canner are in working condition. If canner has a rubber gasket, make sure it is flexible and soft, not brittle, sticky or cracked. Also, check the openings on any small pipes, or vent-ports, to be ensure they are clean and clear of any debris. Finally read the manufacturers instructions.
Once your jars are canned, remember to label the container with the name of the contents and date it was preserved.
With October just around the corner, freezing is another proven method for food preservation. Freezing is an excellent way to preserve fresh vegetables at home. While freezing does not sterilize food, the extreme cold retards growth of microorganisms and slows down changes that affect quality or cause spoilage in food. The quality of frozen vegetables depends on the quality of the fresh products and how they are handled from the time they are picked until they are ready to eat. Buckles agrees. As with any food preservation process, freezing does not improve quality, she said. It can only maintain quality, so be sure the vegetables you freeze are at their peak of freshness. It is imperative to freeze immediately after harvest or purchase.
The selection of freezing containers depends on the product being frozen but at any rate, containers should be moisture-vapor resistant, durable, easy to seal and should not become brittle at low temperatures. Typically used containers, which are suitable for freezing vegetables, include plastic freezer containers, flexible freezer bags, and glass canning jars.
Blanching, or scalding vegetables in boiling water or steam for a short time, is necessary for almost all vegetables to be frozen. According to Buckles, this process stops enzyme actions which can cause loss of flavor, color and texture. In addition, blanching cleanses the surface of dirt and organisms, brightens the color and helps retard loss of vitamins. It also wilts or softens vegetables and makes them easier to pack. Blanching time is crucial and varies with the vegetable and size, explains Buckles. Under-blanching stimulates the activity of enzymes and is worse than no blanching while over-blanching can cause loss of flavor, color, vitamins and minerals.
Learning how to preserve foods can be very satisfying. There is nothing quite like opening a freezer bag of corn on the cob or popping the lid off a quart of homegrown tomatoes in the dead of winter, and catching a whiff of summer all over again.