A starchy food that is initially a single-phase body turns into a multiphase body during boiling because of starch gelatinization. Fick's law is applicable only to a homogeneous system and is not applicable to such a multiphase system. Relative Water Content (RWC) model has been proposed as an alternative model that is able to describe water migration in multiphase food systems. In the RWC model, water migration is driven by the gradient of water content divided by the water holding capacity (WHC), m/m*. In this study a WHC profile (WHC plotted against water content with which starchy food is heat-treated) was assumed based on information concerning starch gelatinization. Using this WHC profile, the correlation between WHC profile and transient water content profile in a wheat flour dough slab during boiling was examined. A modified WHC profile was found to be applicable for describing certain characteristic features of the transient water content profile in a slab of wheat flour dough during boiling.

Water movement in the food processing residues during drying process was discussed to clarify the drying mechanism of the phytogenic residues. Diluted potassium chloride (KCl) solution was added to the residue as a tracer of liquid water. The concentration of KCl at each layer of the residue was measured during drying. The results show that, in the case of bean curd waste, the concentration of KCl at the surface layer increases in the beginning of drying process, and then the KCl of the inner layer becomes higher than that of the surface layer. It means that the direction of liquid water movement in the residue changes locally during drying process. The mass balance analysis using a tank-model shows that the amount of such reverse liquid water in the bean curd waste is about 4%/h of the total moving water

Solid food products are typically in an amorphous state, and their physical properties change dramatically at the glass to rubber transition temperature (Tsub(g)). Tsub(g) decreases with increasing water content because of water plasticizing effects. When Tsub(g) becomes lower than the ambient temperature, a glass to rubber transition occurs at the ambient temperature. The water content at Tsub(g) = 25℃ is usually described as the critical water content (w sub(c)). In this review, the effect of glass to rubber transition on the texture of cookies, the caking of mango powder and the compressibility of soup powder is explained. Tsub(g) of the food samples was evaluated by differential scanning calorimetry or thermal rheological analysis. Wsub(c) was determined from the relationship between Tsub(g) and water content. Fracture properties of the cookie samples changed from brittle to ductile at Wsub(c). Caking of mango powder occurred at water contents above Wsub(c). Hardness of soup powder compressed at temperatures above Tsub(g) was much higher than when compressed at temperatures below Tsub(g).

As for oily water treatment in food industries, the membrane technology has a large potential to reduce the operation time, equipment space and total costs. Using crude lecithin/water emulsion as a model of oily waste water, filtration characteristics on the flux and total organic carbon (TOC) rejection were investigated with a wide range of membranes in reverse osmosis, nanofiltration, ultrafiltration, and microfiltration. Constant flux and TOC rejection were obtained in crossflow filtration with hydrophilic membranes having smaller pores than the emulsion droplets (1-2 mum). Free phospholipids were removed with reverse osmosis membranes or nanofiltration membranes having high NaCl rejection abilities. When microfiltration membranes having larger pores than the emulsion droplets were used, the membrane characteristics such as the pore structure and hydrophobicity largely affected the filtration characteristics: asymmetric membranes gave relatively high fluxes when its loose side was used against the feed emulsion as a depth filter, symmetric membranes having a spongoid pore structure and a pore size similar to the emulsion droplets brought about almost 0 flux owing to an extreme progress of pore blocking, hydrophobic membranes of adequate pore sizes showed a possibility to result in the negative TOC rejection