Understanding the role of vitrification in drying-related phenomena

本研究计划着重于解释食品干燥相关现象，如空气干燥过程中的收缩，菲克定律适用于任何类型的干燥过程，以及通过玻璃化转变的概念优化水果表皮的传质通透性以增强干燥。主要目的是：1)阐明菲克定律是否仅在食物呈玻璃状或橡胶状时才有效；2)了解干燥过程中玻璃化转变对食品物料收缩的作用；3)基于与玻璃化转变的关系，分析利用超低温预处理制备干燥过程中具有选择性渗透性的皮肤和细胞组织生物材料的可能性。玻璃化转变温度Tg可以定义为在非晶体系中从玻璃态转变为橡胶态的温度。在运输过程中，许多食品材料在工业温度和湿度值范围内表现出玻璃化转变。将聚合物玻璃化转变领域的知识应用到食品系统中，已经成功地理解和预测了食品加工过程中的一些行为特征。在食品加工过程中发生的许多其他尚未完全了解的现象也与玻璃化有关。然而，不幸的是，对于这些现象，食品质量、加工和玻璃化转变之间的可量化表达尚未可用，因此，这为食品工程的最新研究发展提供了巨大的机会。最佳干燥技术的潜在演变取决于基础研究的进展和脱水过程设计的创造性水平。这项研究计划将有助于生产“量身定制”的最终产品，通过将基本的物理和化学概念整合到食品加工中，如玻璃化转变，以找到定义食品质量的实际关系，并更好地了解加工对转化产品最终质量的影响。

This research program focuses on the interpretation of food drying-related phenomena such as shrinkage during air-drying, the applicability of Fick's law to any type of drying process, and the optimization of fruit epidermis mass transfer permeability for enhanced drying, through the concept of glass transition. The main objectives are: 1) to elucidate if Fick's law is valid only when the food is in glassy or rubbery states; 2) to understand the role of glass transition in shrinking of food materials during drying; 3) to analyze the possibility of developing biomaterials having skin and cellular tissues with selective permeability during drying by the use of ultra-low temperature pretreatments based on the relationship with glass transition. Glass transition temperature, Tg, can be defined as the temperature at which changes from the vitreous to the rubbery state occur in an amorphous system. Many food materials exhibit glass transition in the range of industrial temperature and moisture values during transport processes. The application of the knowledge learned in the area of glass transition of polymers to food systems had already been successful in understanding and predicting some behavior characteristics of foodstuffs during processing. Many other phenomena occurring during food processing, which are not fully understood yet, have also been related to vitrification. However, quantifiable expressions between food quality, processing and glass transition are unfortunately not yet available for these phenomena thus representing a great opportunity for development of state-of-the-art research in food engineering. The potential evolution of optimal drying techniques depends upon progress in basic research and upon the level of creativity in the design of dehydration processes. This research program will contribute to the production of "tailor-made" final products having desired properties by the integration of basic physical and chemical concepts to food processing, such as glass transition, in order to find practical relationships to define the quality of foodstuffs as well as to better understand the effect of processing on the final quality of transformed products.