the water activity of a solution is equal to 1/100th the relative humidity when expressed as a percent. Water activity is also equivalent to the ratio of the solution's vapor pressure to the vapor pressure of pure water.
An expression of the relative availability of water in a substance. Pure water has a water activity of 1.000. The water activity of a solution is one-hundredth its relative humidity.
A measure of the free moisture in a food. Pure water has a water activity of 1.0 and potentially hazardous foods have a water activity of 0.85 and higher.
A measure of water content equivalent to percent humidity divided by 100.
The amount of water that is available for bacterial growth. Water activity ( Aw ) is the amount of water available for deterioration reactions and is measured on a scale of 0 to 1.0. Bacteria, yeast, and mold multiply rapidly at a high water activity--above 0.86. Meat, produce and soft cheeses have Aw in this range (between 0.86 and 1.0).
Qualitatively, aw is a measure of unbound, free water in a system, available to support biological and chemical reactions. Water activity affects microorganisms survival and reproduction, enzymes, and chemical reactions. The water activity of a substance is quantitatively equal to the vapor pressure of the substance divided by the vapor pressure of pure water (both measured at the same temperature).
Expressed as a w ; refers to the available water or moisture in a substrate expressed as a decimal fraction of the amount present when the substrate is in equilibrium with a saturated atmosphere.
Dependent on its water content, temperature, floral source and other factors, honey's water activity varies between 0.5 (16% H 2 O) and 0.6 (18.3% H 2 O) in the 40-100 °F (4-37 °C) temperature range.
a measure of the moisture available for microbial growth in a product. Measurements range from 0.00 (dry) to 1.00 (pure water).
indicates how tightly water is bound to other molecules in a sample. It is a direct measurement of the free, unbound or "active" water that is available to participate in chemical reactions.
Water activity is a measure of the amount of free unassociated water molecules in a system. It runs on a scale of 0 to 1.0, where pure water equals 1.0. This parameter can also be expressed as a percentage referred to as the relative humidity. It is influenced by dissolved solutes and insoluble food components which act to bind water, thus reducing the available free water and hence aW value.
is a measure of the free moisture in a component, dietary ingredient, or dietary supplement and is the quotient of the water vapor pressure of the substance divided by the vapor pressure of pure water at the same temperature. [Definition from Proposed Rule: Current Good Manufacturing Practice in Manufacturing, Packing, or Holding Dietary Ingredients and Dietary Supplements; 68 FR 12251
Water activity or aw is the relative availability of water in a substance. It is defined as the vapor pressure of water divided by that of pure water at the same temperature; therefore, pure distilled water has a water activity of exactly one.
