Before the rise during industrialization of refrigeration, artificial preservatives, vacuum sealing and freeze drying, most foods were cured using a mixtures of salt and sugar. Sugar and salt curing is often combined with smoking. Salt and sugar act to increase osmotic pressure destroying some bacteria and slowing decay, promote the growth of beneficial bacteria and work together to improve taste.
About Sugar and Salt Curing
Many foods decay very rapidly after harvesting, especially meats. A combination of salt and sugar reduces the water content of meats, fruits and vegetables aiding in preservation. In meats sugar and salt curing is typically accompanied by smoking or some other cooking method. Most preservation methods used since ancient times attempt to reduce water content to between 10 and 50 percent, a level that reduces decay but maintains palatability.
Effects of Salt
Sodium chloride or table salt is the main ingredient used in the preservation of meats. Salting meat draws water out and tying up the water within, making it unavailable for chemical reactions that cause decay. High concentrations of salt also interfere with the replication of microorganisms such as bacteria.
Salt curing frequently uses salts containing nitrates. Nitrates act as antioxidants in preserved foods, preventing decay and spoilage through oxidation and free radical generation. However, high consumption of preserved foods containing nitrates may be linked to a higher risk of cancer.
Effects of Sugar
Just like with salt, some forms of sugar can draw water out of food and tie up water within the food so it is not available for biochemical reactions. According to the Food and Agriculture Organization, fructose and sucrose are very effective for preserving food while glucose is not. Sugar may also encourage the growth of healthy bacteria that prevent bacteria that will make you sick from growing. High concentrations of sugar also exert osmotic pressure that will draw water out of bacteria, preventing them from growing.
Water Content in Preserved Foods
At lower water content, bacterial, fungal and mold growth is inhibited and the enzymatic and non-enzymatic decay of food is slowed. Preserved foods should be kept in a cool and dry environment to discourage bacterial growth and spoilage. Most food preservation techniques currently used, combine methods of smoking, drying, sugar and salt, preservatives, refrigeration, acidity and others with the idea that bacteria and other microorganisms cannot jump over all the hurdles in place.