Optimization of leaf protein extraction process and key parameters of Medicago polymorpha in the agricultural areas of Lower Yangtze River

The objective of this study was to improve and optimize the process of extracting leaf proteins from Medicago polymorpha and to improve the extraction rate of leaf proteins and extract purity. M. polymorpha was selected for this study and is widely cultivated in the agricultural areas of the lower reaches of the Yangtze River as a raw material. A single factor test for leaf protein extraction was carried out by setting a reasonable and scientific material-liquid ratio, extraction temperature, heating time, pH, and extractant (acid) type. The results showed that the optimal parameters of each single factor test were: 1∶3 material-liquid ratio; 70 °C extraction temperature; 15 min heating time; pH 4.0; and a hydrochloric acid extractant. Based on the clean and safe production angle, citric acid with the same high extraction rate for the single factor test was selected as the extractant, and the 3 factors and 3 level responses of the surface test of the material-liquid ratio, pH, and extraction temperature were set. It was found that the extraction rate of leaf proteins was affected, and the order of these factors was pH, extraction temperature, and material-liquid ratio. The optimal extraction process was: 1∶3 ratio of material to liquid, pH 4.1, 72 °C extraction temperature, 49.63% leaf protein extraction rate, and a 56.87% extract purity rate. The optimized technical process and related parameter indicators of this experiment can provide certain technical support and related references for the diversified utilization of leguminous plants in agricultural areas and the industrial production of leaf proteins.