Is Water Activity the Same as Moisture Content

Moisture content defines the amount of water in your food and ingredients, but water activity explains how the water in your food will react with microorganisms.

What is meant by water activity?

The water activity (a w) of a food is the ratio between the vapor pressure of the food itself, when in a completely undisturbed balance with the surrounding air media, and the vapor pressure of distilled water under identical conditions. … The water activity increases with temperature.

What is determination of moisture content?

Typically, moisture content is determined via a thermogravimetric approach, i.e., by loss on drying, in which the sample is heated and the weight loss due to evaporation of moisture is recorded. … However, the reference method for loss on drying (drying oven method) can take many hours to reach a result.