Abstract:Rice bran is anutritional by-product of brown rice，which contains richrice bran protein，one of the high-quality vegetable proteins.However，the low extraction yield and low solubilityof the protein result in a waste ofresources.Therefore，it is of great significance to study the extraction process.This study aimed to improve the extraction yield of rice bran protein for utilization.This study extracted rice bran protein was by ultrafine grinding combined with ultrasound and explored the effects of extraction conditions on the yield.The extraction conditions were optimized by response surface methodology.Furthermore，the solubility of rice bran protein was compared between the optimized extraction process and the conventional process（alkali-extraction and acid-precipitation）.The results showed that solid-liquid ratio，ultrasound time，and extraction time had significant effects on the yield of rice bran protein（P＜0.05）.The optimum extraction conditions of rice bran protein were as follows：solid-liquid ratio 1 ∶57（g/mL），extraction for 4 h and ultrasound for 9 min.Under these conditions，the yield of rice bran protein reached（64.31±0.18）%，which was 41.62%higher than that of the conventional process.The solubility of the rice bran protein extracted with the optimized process was 25.49%，which was significantly higher than that of the protein obtained with the conventional process.Ultrasound combined with ultrafine grinding can significantly increase the extraction yield of rice bran protein，which provides theoretical reference for the extraction and utilization of rice bran protein.