Understanding the role of vitrification in drying-related phenomena

该研究计划的重点是食品干燥相关现象的解释，如空气干燥过程中的收缩，菲克定律对任何类型的干燥过程的适用性，以及通过玻璃化转变的概念优化水果表皮传质渗透性以增强干燥。主要目标是：1）阐明Fick定律是否仅在食品处于玻璃态或橡胶态时有效; 2）理解玻璃化转变在干燥过程中食品材料收缩中的作用; 3）基于与玻璃化转变的关系，分析通过使用超低温预处理开发具有在干燥过程中具有选择性渗透性的皮肤和细胞组织的生物材料的可能性。玻璃化转变温度Tg可以定义为无定形体系中从玻璃态转变为橡胶态的温度。许多食品材料在运输过程中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于食品系统，已经成功地理解和预测了食品在加工过程中的某些行为特征。在食品加工过程中发生的许多其他现象，尚未完全了解，也与玻璃化有关。然而，不幸的是，食品质量，加工和玻璃化转变之间的量化表达式尚未提供这些现象，从而代表了一个伟大的机会，发展国家的最先进的研究食品工程。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。该研究计划将有助于通过将基本物理和化学概念整合到食品加工中来生产具有所需特性的“量身定制”最终产品，例如玻璃化转变，以便找到实际关系来定义食品的质量以及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.