Antiplasticization by water in reduced-moisture food systems

Antiplasticization of synthetic glassy polymers by low-molecular weight diluents at low concentrations is a well-known phenomenon which leads to increased rigidity rather than flexibility of the polymer-diluent blends. Based on the food polymer science approach, we hypothesized that increases (rather than decreases) in modulus and brittleness, commonly observed when certain solid food systems are humidified from the dry state, are synonymous with antiplasticization by water. Sugars and polyols, important components of foods, behave in much the same manner as water in acting as either antiplasticizers or plasticizers of food polymer systems. Several mechanisms may be involved in antiplasticization by low-molecular mass diluents, Simultaneous changes in various physical properties, resulting from antiplasticization or plasticization by water and other diluents, may profoundly influence the quality and acceptability of food products.