A Finite Element Analysis of Coupling Between Water Absorption and Swelling of Foodstuffs During Soaking

Most foodstuffs are viscoelastic in nature and they experience volume change when soaked. Moisture transport affects the volume change of foodstuffs in a soaking process and vice versa. Studies of soaking of foodstuffs that involve rigorous two way coupling between simultaneous moisture transport and large viscoelastic deformation of the material are missing, to the best of the authors’ knowledge. In this article, these two important phenomena, i.e., swelling and moisture transport during a soaking process of foodstuffs are coupled non-empirically based on a fundamental mathematical model developed by Zhu et al. (Transp Porous Media 84:335–369, 2010 ). A finite element analysis is performed to study boiling of plane sheet pasta at 100°C. This coupling of the transport and deformation problems is carried out using a Newton scheme based on a Lagrangian description of the spatial domains. In this study, the dependence of relaxation modulus of pasta on the moisture content is investigated, starting from data in the literature, and it is found from the results that pasta can be considered as a hydro-rheologically simple viscoelastic material as analogous to a thermo-rheologically simple material. A novel theoretically determined expression of the diffusion coefficient is also used to completely separate the viscoelastic effect from diffusion. Sorption curves are calculated and the predictions agree well with experimental results obtained by Cafieri et al. (J Cereal Sci 48:857–862, 2008 ). Thickness change of plane sheet pasta and the stress field at different times are also calculated. The numerical model presented here can be successfully used to predict simultaneous moisture migration and swelling of viscoelastic food materials during a soaking process.