Effect of drying methods on the physicochemical properties and adhesion performance of water-washed cottonseed meal

Abstract

Water-washed cottonseed meal (WCSM) showed the potential for being used as environment-friendly wood adhesives. However, the influence of WCSM preparation process on its adhesion performance is not well known. This work studied the effect of different drying methods on the several key physicochemical features and adhesion performance of WCSM. Defatted cottonseed meal was washed with 8 folds of water for 3 cycles to remove the water-soluble components and dried with oven, freeze dryer, and spray dryer, respectively. Whereas the major chemical composition was unchanged, oven-dried WCSM showed protein degrading denaturation per sodium dodecyl sulfate polyacrylamide gel electrophoresis and differential scanning calorimetry data. With hot press temperature at 100°C, oven-dried WCSM showed poor adhesion performance when compared with its freeze- and spray-dried counterparts. However, the difference among the products with the three drying methods became smaller, and even none with the press temperature at 150 and 170°C. The adhesion performance could be further improved by pH 4.5 adjustment and removal of large residual hull particles. This study proved spray-drying and freeze-drying more suitable to make high quality cottonseed meal-based adhesives for a variety of operation conditions. On the other hand, the more economic oven-drying may be applied to make WCSM product for bonding at higher press temperature (e.g. 170°C) without undermining WCSM’s adhesion performance.