TI Food and Nutrition, PO Box 557, NL-6700 AN Wageningen, The Netherlands.
J Sci Food Agric. 2011 Nov;91(14):2537-43. doi: 10.1002/jsfa.4386. Epub 2011 Mar 29.
Water migration in cellular solid foods during storage causes loss of crispness. To improve crispness retention, physical understanding of this process is needed. Mathematical models are suitable tools to gain this physical knowledge.
Water migration in cellular solid foods involves migration through both the air cells and the solid matrix. For systems in which the water migration distance is large compared with the cell wall thickness of the solid matrix, the overall water flux through the system is dominated by the flux through the air. For these systems, water migration can be approximated well by a Fickian diffusion model. The effective diffusion coefficient can be expressed in terms of the material properties of the solid matrix (i.e. the density, sorption isotherm and diffusion coefficient of water in the solid matrix) and the morphological properties of the cellular structure (i.e. water vapour permeability and volume fraction of the solid matrix). The water vapour permeability is estimated from finite element method modelling using a simplified model for the cellular structure.
It is shown that experimentally observed dynamical water profiles of bread rolls that differ in crust permeability are predicted well by the Fickian diffusion model.
在储存过程中，细胞状固体食品中的水分迁移会导致其丧失脆性。为了提高脆性保持性，需要对这一过程有物理层面的理解。数学模型是获取这种物理知识的合适工具。
细胞状固体食品中的水分迁移涉及通过空气细胞和固体基质的迁移。对于水迁移距离与固体基质细胞壁厚度相比很大的系统，通过系统的总水流主要由空气的流决定。对于这些系统，水分迁移可以很好地用菲克扩散模型来近似。有效扩散系数可以用固体基质的材料特性（即固体基质中的密度、吸附等温线和水分扩散系数）和细胞结构的形态特性（即水蒸气渗透率和固体基质的体积分数）来表示。水蒸气渗透率是使用简化的细胞结构模型通过有限元方法建模来估计的。
研究表明，具有不同外壳渗透率的面包卷的实验观测到的动态水分分布可以很好地用菲克扩散模型来预测。
