Few things taste better than fresh picked fruits and veggies straight from gardens and farmers’ markets. Garden produce can be enjoyed not only at harvest time but throughout the year thanks to real sugar and salt—all-natural ingredients which have played an important role in food preservation methods such as canning for centuries.
“Both sugar and salt have unique preservation properties besides imparting flavor to foods,” said Julie Garden-Robinson, Ph.D, R.D., L.R.D, extension specialist and professor in Nutrition and Food Safety at North Dakota State University in Fargo. “In the right concentration, sugar and salt can delay or stop the growth of microorganisms and help preserve the quality and safety of food products.”
Salt has been used since prehistoric times and the ancient Egyptians were the first to realize its possibilities for food preservation. The earliest method of curing meat was dehydration because sodium draws the bacteria-causing moisture out of foods, drying them and making it possible to store meat for extended periods of time.
“Earlier generations discovered that ‘salting,’ or brining foods in a saltwater mixture, helped maintain the safety of perishable foods such as meats and cucumbers,” said Garden-Robinson. “Sugar also has a long history of use in food preservation.”
The world’s first known cookbook, “De Re Coquinaria,” or “The Art of Cooking,” is a collection of Roman recipes attributed to Marcus Gavius Apicius and believed to have originated in the first century AD. It contained the first recipe for jam, which in its simplest form was heated fruit with sugar.
“People learned that making jams and fruit sauces with sugar-containing syrups helped the foods remain safer longer,” Garden-Robinson said. “Over time, scientists determined the natural aspects of sugar and salt in preserving food, especially when combined with further processing such as drying or heating.”
Sugar does more than just lend its characteristic sweet flavor to jams, syrups, and fruit sauces. It also allows the fruit to maintain its shape in some cases, according to Garden-Robinson.
“Sugar also interacts with pectin, the gelling agent in jams, to create a thick product. The combination of sugar and natural acids in fruit helps slow the growth of bacteria,” she said.
Microorganisms, or “germs,” need a certain amount of water present to grow. Foods vary in their “water activity,” which is measurable with an instrument called a “water activity meter,” and have water activity values ranging from 0 to 1.0, which is pure water.
“Most types of bacteria need a water activity of 0.85 or greater to grow. Salt and sugar can both reduce the water activity in foods. When used in preservation, salt and sugar are solutes that compete for the available water in foods, making the water less available to microorganisms,” explained Garden-Robinson. “Sugar also has humectant properties, meaning that it draws water toward itself. At the appropriate level in jam, jellies and other foods, sugar can stabilize the water activity and keep food safer longer in the cupboard or in the refrigerator.”
Both sugar and salt play an important role in canning, which was pioneered in the 1790s by French confectioner Nicolas Appert. Appert discovered that the application of heat to food in sealed glass bottles preserved the food from deterioration. His principles were successfully trialed by the French navy on a wide variety of foods including meat, vegetables, fruit and even milk, and a new food preservation method was born.
Today, granulated table sugar is the most frequently used sweetener in canning and freezing because it helps preserve the color, texture, and flavor of the food. Sugar and salt also play starring roles in fermentation. In cheesemaking, salt not only adds to the flavor of the cheese, but it also helps with texture development, regulates moisture, and preserves the cheese as it ages. Sugar is essential to making fermented beverages including ales, lagers, porters, and stouts.
It is critical to use research-tested recipes vetted by food scientists for any food preservation activity and follow them exactly, said Garden-Robinson.
“Adding a sprinkle of sugar or salt to food does not mean that the addition has preservative effects. Sometimes salt and sugar are for flavor and sometimes they are for preservation,” she said. “For example, in jerky recipes, the added salt has a preservative effect and should not be changed in the recipe or reduced in quantity. If less salt were used in a dried meat recipe, then the product would not necessarily be safe. If, however, you were preserving green beans as directed in a pressure canner, you could leave out the salt because the salt is present to add flavor and not for safety.”
Garden-Robinson said there are times when small changes can be made in tested recipes and still result in a safe, high-quality product. She urges people to seek out up-to-date information about food preservation and be wary of information found in old cookbooks.
“Times have changed since our grandparents and great-grandparents day, and the speed that inaccurate information can be spread continues to accelerate,” she said. “Untested food preservation information can be hazardous to people’s health, or in the worst case, have fatal consequences.”
Garden-Robinson recommends everyone be aware of the role of Cooperative Extension at land grant universities throughout the US.
“Online resources and both online and face-to-face training are widely available, and tested home food preservation recipes with processing methods and times can be found at www.ag.ndsu.edu/food,” she said. “Also, a recent publication called ‘Play it Safe! Safe Changes and Substitutions to Tested Canning Recipes’ was created by food safety specialists in the Midwest and illustrates what you can and cannot safely change.”
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