Moisture loss, gain and migration in foods

International audienceThe loss, gain and transfer of moisture often affect food materials. Whether arising from interaction with the atmosphere or with another component of the food, such changes always cause deterioration of the overall quality of the food through softening, toughening, breakdown, swelling or shrinkage due to phase transitions or dissolution. In most cases, water migration leads to organoleptic or microbiological changes in the food. With a view to better understanding the physical deterioration of food and to providing a tool for better control of food quality (and therefore of longer shelf life), this chapter reviews the water relationships in foods with particular attention to, and illustration of, glass transition-related phenomena. It also considers examples of foods affected by moisture exchanges with the atmosphere or within the product itself. The mechanisms controlling these migrations are presented together with some experimental approaches (measurements of moisture content, water activity and migration and modelling)