Optimization of microwave-assisted extraction process and properties of protein from Plukenetia volubilis

【Objective】To enhance the extraction methodology of Plukenetia volubilis protein and investigate its processing characteristics to provide reference for the advanced processing and utilization of P. volubilis protein. 【Method】A microwave-assisted alkali dissolution-acid precipitation method was used to extract P. volubilis protein(denoted as MAPP) from its cake. Based on a single-factor test, the extraction process was optimized by response surface methodology using liquid-to-material ratio(A), microwave power(B) and microwave time(C) as independent variables and MAPP yield(Y) as response value. Furthermore, the effects of varying temperatures and pH on MAPP's processing properties were investigated, which were compared with alkali dissolution-acid precipitation extracted P. volubilis protein(denoted as APP). 【Result】The effects of the three factors on the MAPP yield were ranked as microwave power>liquid-tomaterial ratio>microwave time, in which the effect of microwave power was extremely significant(P<0.01,the same below), and the effects of the three interaction items were not significant(P>0.05), and the model optimization equation was Y=14.42+0.5075A+1.05B+0.4838C+0.0425AB+0.4225AC-0.1350BC-1.25A²-1.13B²-0.8725C². The optimal process conditions for MAPP extraction were obtained: liquid-to-material ratio of 17∶1(mL/g), microwave power of 645W, and microwave time of 62 s. Under these conditions, the protein yield was 14.46%, and the protein purity was 90.29%, which was higher than that of the APP yield(13.24%). The heat treatment at 60 ℃ enhanced the solubility of P.volubilis protein, the water holding rate and oil holding rate were the largest at 50 ℃; when the pH was 2 or 9, the solubility of P. volubilis protein was high, and its foaming and foaming stability, emulsification and emulsion stability were the highest; compared with APP, the solubility and water holding rate of MAPP were extremely significantly increased at 60 and 70 ℃, and the oil holding rate of MAPP was higher than that of APP in the range of 20-60 ℃, the solubility of MAPP was extremely significantly improved in the pH range of 4-7; the foaming and foaming stability, emulsification and emulsion stability were improved under the appropriate pH conditions. 【Conclusion】Microwave-assisted alkali dissolution-acid precipitation can increase the protein yield of P. volubilis and improve its processing properties.