Recycling of food-by-products is very important subject. Many trials have been done to reuse by-product, however, almost trials have not been to install the commercial process due to their treatment costs and their qualities. To convert biodegradable stuff is one of their trail fields. However, their products have disadvantage of high cost and low properties against water-resistance. To minimize costs and to improve waterproof property, we used zein-containing corn gluten meal and succeeded in making solid materials by injection molding. We turned the materials into pellets with an extruder, and then molded the pellets into seedling culture pots with an injection molder. This study project was carried out jointly with Showa Sangyo Co., The Japan Steel Works and National Food Research Institute. In this project we were able to successfully reduce costs and to obtain solid molded products for practical use by adopting the injection molding method, which has many advantages in productivity (low costs, high moldability, flexibility to make various shapes of molds). At present, we are working to assess the biodegradable molded material actually applied and to improve materials for different purposes.

The state of water in foodstuffs is a guiding principle in food design, and the equilibrium concept of water activity (Aw) is ubiquitous. It is regarded as a primary variable or “hurdle” in preservation technology, and a key variable influencing chemical reaction during storage. However, the amount of water in any system differs as function of water activity depending whether it is determined by water sorption or desorption. Even though this hysteresis behaviour has already been described in the literature, no physical interpretation of its origin has yet been proposed with respect to detailed molecular organisation. This work shows, for two different food powders, gluten and a milk-based product that the hysteresis disappears when either go through their glass transition. A more complete DSC analysis for gluten during different sorption/desorption cycles demonstrates that the hysteresis is dependent on the ageing of the material, which evolves in the glassy state and is induced by structural relaxation.

Relation between the thermodynamic parameters obtained from water sorption isotherms and the degree of reduction in the glass transition temperature (Tg), accompanied by water sorption, was quantitatively studied. Two well-known glassy food materials namely, wheat gluten and maltodextrin were used as samples. The difference between the chemical potential of water in a solution and that of pure water (), the difference between the chemical potential of solid in a solution and that of a pure solid (), and the change in the integral Gibbs free energy () were obtained by analyzing the water sorption isotherms using solution thermodynamics. The parameter correlated well with ΔTg (≡Tg − Tg₀; where Tg₀ is the glass transition temperature of dry material), which had been taken to be an index of plasticizing effect. This indicates that plasticizing effect of water on foods can be evaluated through the parameter .

The relationship between structural and foaming properties of two tryptic and two peptic wheat gluten hydrolysates was studied at different pH conditions. The impact of pH on foam stability (FS) of the samples heavily depended on the peptidase used and the degree of hydrolysis reached. Surface dilatational moduli were in most, but not all, instances related to FS, implying that, although the formation of a viscoelastic protein hydrolysate film is certainly important, this is not the only phenomenon that determines FS. In contrast to what might be expected, surface charge was not a major factor contributing to FS, except when close to the point-of-zero-charge. Surface hydrophobicity and intrinsic fluorescence measurements suggested that changes in protein conformation take place when the pH is varied, which can in turn influence foaming. Finally, hydrolyzed gluten proteins formed relatively large particles, suggesting that protein hydrolysate aggregation probably influences its foaming properties.