Water activity

Water activity (aw) measures the availability of water in a substance for microbial growth and chemical reactions. It is expressed as a number from 0 to 1, where 1 represents pure water. Low water activity means water is less accessible, helping foods stay fresh longer and preventing spoilage. For example, dried foods have low water activity, making them less prone to microbial growth. Conversely, high water activity in fresh fruits or meats indicates more free water, increasing the risk of bacteria and mold growth. Understanding water activity helps in food preservation, safety, and quality control.