Optimization of Extraction Process and Analysis of Physicochemical Properties of Wild Rice Protein

Wild rice was used as raw material to extract protein by alkali extraction and acid precipitation. Based on the single-factor test, the best extraction process of wild rice protein was obtained by using the index of extraction rate of rice protein and the optimization of the response surface method. The wild rice protein powder was obtained by isoelectric point precipitation and freeze-drying. Compared with the Huai rice protein extracted under the same conditions, wild rice protein's molecular composition, thermal stability, and digestion characteristics were compared and analyzed. The results showed that the effects of different extraction conditions on the extraction of wild rice protein by alkali extraction and acid precipitation were as follows: Ratio of material to liquid>temperature>time, and the optimum extraction conditions were as follows: Extraction temperature 58 ℃, the ratio of material to liquid 1:25 g/mL, extraction time 3.5 h. Under these conditions, the wild rice protein extraction rate was 45.97%, and the isoelectric point (pH) of wild rice protein was 3.5. Compared with Huai rice protein, the denaturation peak temperature of wild rice protein was 108.4 ℃, ΔH=164.4 J/g, the high molecular weight protein content was less, and the digestibility was the same, however, the content of free amino acids was always higher, which was more beneficial to human digestion and absorption. In conclusion, wild rice protein is a high quality source of supplemental protein for human body.