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How do salt and sugar help preserve food?
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gastronomy
A common rice dish of Japanese cooking is sushi. To make a type known as maki-zushi, a sheet of seaweed is spread with rice flavored with vinegar. Seafood or vegetables and garnishes are then placed on top. Finally, the whole sheet is rolled into a cylinder and sliced.
Salt and sugar preserve food primarily by controlling water activity, which is the amount of available water in a food product that microorganisms need to grow and reproduce.12
By adding high concentrations of these solutes to food, the concentration of available water decreases. This process creates an environment where microbial growth is retarded or prevented. The mechanism relies on the principle of osmosis, where the presence of solutes draws water out of microbial cells or binds it so that it is no longer accessible to bacteria, molds, and yeasts.13425
Specific applications include:
- Salt: As one of the oldest known antimicrobial agents, salt is widely used in the meat-packing, fish-curing, and pickling industries. It effectively lowers water activity, and some bacteria, known as halophiles, are among the few that can tolerate high salt concentrations.672
- Sugar: Used extensively in making jams, jellies, and marmalades, sugar is added to reach high concentrations of soluble solids—often 65 percent or more—which creates a shelf-stable environment. It is also used in the process of candying fruit to prevent spoilage.483
By reducing water activity, both substances effectively delay or inhibit the spoilage mechanisms that would otherwise lead to food deterioration.328