Understanding the role of vitrification in drying-related phenomena

这项研究计划侧重于解释与食品干燥相关的现象，如空气干燥过程中的收缩现象，费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面强化干燥的传质渗透率。主要目的是：1)阐明菲克定律是否只有在食品处于玻璃态或橡胶状态时才适用；2)了解玻璃化转变在食品干燥过程中收缩的作用；3)根据玻璃化转变与玻璃化转变的关系，分析利用超低温预处理开发具有皮肤和细胞组织在干燥过程中具有选择性渗透性的生物材料的可能性。玻璃化转变温度Tg可以定义为非晶态玻璃向橡胶状态转变的温度。在运输过程中，许多食品材料在工业温度和湿度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体系中，已经成功地理解和预测了食品在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现象也与玻璃化有关，这些现象还没有完全被理解。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尚不能用于这些现象，因此为食品工程最新研究的发展提供了巨大的机遇。最佳干燥技术的潜在演变取决于基础研究的进展和脱水工艺设计的创造性水平。这项研究计划将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，来帮助生产具有所需特性的“定制”最终产品，以便找到实用的关系来定义食品质量，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.