(405b) Heat and Acid-Induced Hydrogels from Soybean Hull: Effect of Processing Conditions

Gels are semisolid materials with a liquid phase entrapped in a three-dimensional network structure. Based on the textural and rheological properties, these materials provide many applications in the food, biomedical, pharmaceutical, and cosmetics industries. In recent years, natural polymer-based hydrogels (water-based gels) have been a topic of several studies due to their advantages (biocompatibility, biodegradability, accessibility, and renewability) over synthetic hydrogels. Most natural hydrogels are produced from pure/fractionated ingredients, such as pectin, protein, alginate, chitosan, and starch. In this study, we applied thermo-chemical treatment on soybean hull (SBH) to produce hydrogels. SBH is one of the major byproducts of the soy industry, with a global annual production of approximately 20 million tons, with ~50% from the US only. Despite the large amount generated, SBHs have received minimal attention as low-cost raw materials, and their applications are limited to animal feed and dietary fiber, while most of them are still left to waste. We hypothesized that SBH is a promising candidate for hydrogel production because of its unique chemical composition (high pectin and protein content). Our goal approach in the current study was to produce hydrogels from SBH without extracting specific components, leading to a cost-effective and environmental-friendly process generating minimal effluent. The properties of produced hydrogels are significantly affected by the applied processing conditions. Time, temperature, and pH of treatments were chosen as the independent factors, and a three-level face-centered central composite design (CCD) was used as the statistical method for the design of experiments (DOE). Selected levels of processing conditions are as follows: (T: 65-95℃, t: 10-60 min, pH: 1.8-5.8). The effect of each processing condition and their interactions on the yield, water content, pectin/protein ratio, and viscoelasticity of the resulting hydrogels were evaluated using response surface methodology (RSM).