تعيين شرايط بهينه استخراج پلي ساكاريدهاي محلول از ُاكارا

Optimization of the Extraction of Soybean Soluble Polysaccharides from Okara

Background and objectives: Soybean soluble polysaccharides (SSPS) are a food additive with various applications, including the stabilization of emulsions and dairy-based acid beverages. They are normally extracted from okara, a waste product in the production of soy products. In this study the feasibility of the extraction of SSPS from dried okara with and without demethoxylation and from wet okara (obtained in the process of soy milk extraction) with demethoxylation was investigated. Materials and methods: In order to optimize the demethoxylation conditions, the response surface methodology (RSM) was used and demethoxylation was carried out at different temperatures (60, 75 and 90°C) and okara:water ratios (1:6, 1:8 and 1:10). Different types of SSPS were extracted at various temperatures (120 and 130 °C), pHs (3 and 4.5) and heating times (2 and 3 h). Then, the extracted juices were purified (using ethanol for precipitation of high-molecular weight SSPS), dehydrated, and analyzed. Results: Each one of the independent variables (demethoxylation temperature and okara:water ratio) was linearly related to the response (total soluble solids extracted), the effects being statistically significant (P<0.01 and P0.0001, respectively). In addition, the total soluble solids increased at high extraction temperature and low pH conditions. The findings also showed that pH was an important factor in the extraction of high-molecular weight SSPS (HM-SSPS). Furthermore, when the demethoxylation process was used, the maximum yield of HM-SSPS (22.4%±1.04%) was achieved at the following conditions: 130 °C, 3h, and pH=4.5; on the other hand, without demethoxylation the highest yield (30.8%±1.6%) was obtained at these conditions: 120°C, 2 h, and pH=4.5. Conclusions: The soymilk okara was found to be a feasible natural source for the extraction of various types of SSPS. Our findings also revealed that the dehydration of wet okara could prevent its spoilage and improve the yield of SSPS.