What is the minimum water activity level at which bacteria will grow?

Bacteria require a certain level of moisture to grow, which is measured using water activity (aw). The minimum water activity level that supports the growth of most bacteria is generally 0.85 or higher. At this level, there is sufficient water available for microbial growth, as bacteria need water to carry out metabolic processes and reproduce.

A water activity level below 0.85 typically inhibits the growth of most pathogenic and spoilage bacteria, making 0.85 the critical threshold for potential bacterial growth in food. This understanding is essential in food safety practices to prevent foodborne illnesses.

Options with lower water activity levels, such as 0.70 or 0.80, do not provide the necessary moisture for most bacteria to thrive, which reflects why those choices do not indicate the minimum required level for bacterial growth.