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The water in food has a tendency to evaporate, but the water vapor in the surrounding air has a tendency to condense into the food. When the two tendencies are in balance— and the air and food are stable—the air's relative humidity (expressed as a fraction instead of as a percentage) is taken to be the water activity, a w .
Intermediate moisture foods (IMF) are shelf-stable products that have water activities of 0.6-0.85, with a moisture content ranging from 15% - 40% and are edible without rehydration. [1] These food products are below the minimum water activity for most bacteria (0.90), but are susceptible to yeast and mold growth .
Water is essential for the growth of foodborne pathogens. Water activity (a w) is a measure of the water available for use and is measured on a scale of 0 to 1.0. Foodborne pathogens grow best in foods that have a w between 0.95 and 1.0. FDA regulations for canned foods require a w of 0.85 or below.
Food moisture analysis is the determination of the concentration of water in a food sample. A variety of techniques may be used including Karl Fischer titration and loss on drying. Many technical standards exist which define test methods for determining moisture in different types of food.
Both vary in the reaction rate as a function of water activity (in food chemistry, the standard state of water activity is most often defined as the partial vapor pressure of pure water at the same temperature). Caramelization is a process involving the pyrolysis of sugar. It is used extensively in cooking for the desired nutty flavor and brown ...
Download as PDF; Printable version; ... Nutrition, and for how food is digested see Category:Digestive system ... Water activity This page was last ...
These humectant food additives are used for the purpose of controlling viscosity and texture. Humectants also add bulk, retain moisture, reduce water activity, and improve softness. A main advantage of humectant food additives is that, since they are non-ionic, they are not expected to influence any variation of the pH aqueous systems. [8]
Potentially Hazardous Food is a term used by food safety organizations to classify foods that require time-temperature control to keep them safe for human consumption. A PHF is a food that: Contains moisture – usually regarded as a water activity greater than 0.85; Contains protein