Water activity (aw) is a measure of the availability of water for microbial growth and chemical reactions in food. It ranges from 0 (completely dry) to 1 (pure water). Water activity significantly affects the shelf life and safety of foods in several ways:

1. Microbial Growth:

• High water activity (above 0.85) supports the growth of bacteria, yeast, and molds. This can lead to spoilage and foodborne illnesses.

• Lowering water activity (below 0.85) inhibits microbial growth, extending the shelf life of food. Foods like dried fruits, jerky, and certain baked goods maintain lower water activity to prevent spoilage.