Department of Food and Nutritional Sciences, University College Cork, Ireland.
Annu Rev Food Sci Technol. 2010;1:469-96. doi: 10.1146/annurev.food.102308.124139.
Amorphous, noncrystalline solids are typical of low water content and frozen foods. Solids in these foods, e.g., confectionary, dehydrated foods, cereal foods, and frozen foods, often form nonequilibrium glass-like structures. The glassy state of the solids forms during food processing in a reversible glass transition. Vitrification can occur in numerous glassy states that exhibit various relaxations around the glass transition. The success of freeze drying, spray drying, and extrusion and the stability of dehydrated foods against flow, collapse, and crystallization is based on the control of the glassy state during the dehydration process and storage. Encapsulation processes often use glass-forming materials to entrap dispersed components or improve retention of volatiles. Plasticization of the noncrystalline structures by temperature or water reduce relaxation times exponentially above the glass transition, which results in rapid deterioration. Critical values for water activity and water content express the level of water plasticization leading to glass transition in food storage.
非晶态、无定形固体是低水分和冷冻食品的典型特征。这些食品中的固体，如糖果、脱水食品、谷物食品和冷冻食品，通常形成非平衡的玻璃状结构。固体的玻璃态在食品加工过程中通过可逆的玻璃化转变形成。玻璃化可以发生在许多玻璃态中，这些玻璃态在玻璃化转变周围表现出各种弛豫。冷冻干燥、喷雾干燥、挤压以及脱水食品对流动、崩溃和结晶的稳定性的成功，基于在脱水过程和储存过程中控制玻璃态。包封过程通常使用形成玻璃的材料来捕获分散的成分或改善挥发性物质的保留。通过温度或水对非晶结构的增塑作用，使玻璃化转变上方的弛豫时间呈指数级减少，从而导致快速劣化。水活度和水分含量的临界值表示在食品储存中导致玻璃化转变的水增塑水平。
