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How do refrigeration and freezing slow the growth of microorganisms in food?
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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.
In the field of food science, refrigeration and freezing are essential methods of low-temperature preservation used to extend the shelf life of food by inhibiting the growth of microorganisms.12
Mechanisms of Microbial Inhibition
Microorganisms, such as bacteria, require specific conditions to thrive, including optimal temperatures, moisture, and nutrients. Low-temperature storage slows these processes in two primary ways:3
- Reduced Metabolic Rates: Microorganisms are classified by their temperature requirements for growth (e.g., thermophiles, mesophiles, and psychrotrophs). By lowering the temperature, the kinetic energy available for the chemical and physical reactions necessary for microbial metabolism and binary fission is significantly reduced.31
- Water Availability: Freezing converts liquid water into ice, which reduces the amount of water available for microbial use. Since bacteria require a certain level of water activity to grow, the transition of water to a solid state effectively limits their ability to proliferate.43
While these methods retard deterioration, it is important to note that they do not necessarily destroy all microorganisms; some may remain dormant as endospores and resume growth if conditions become favorable again, such as during thawing.3