Optimization of the Extraction Process, Structural Characterization and Antioxidant Activity of Ginseng Alcohol Soluble Proteins

To explore the extraction process, structural characterization and in vitro antioxidant activity of alcohol soluble proteins from ginseng. This study used ginseng as the research object, explored the optimal extraction process of ginseng alcohol soluble protein by one-way test and response surface test, structurally characterized ginseng alcohol soluble protein by ultraviolet absorption spectrometry, infrared spectrophotometric analysis, amino acid composition, and microstructure observation, and carried out a series of studies on its antioxidant activity in vitro under different pH conditions. The in vitro antioxidant activity of ginseng alcohol soluble protein was evaluated by determining the DPPH radical scavenging capacity, ·OH scavenging capacity, and iron ion reduction capacity. The results showed that the optimal extraction process of ginseng alcohol soluble protein was 2 h, extraction material-liquid ratio of 1:10 g/mL, and extraction pH of 7, at which the yield of ginseng alcohol soluble protein was 0.319% and the protein content was 75%. The results of ultraviolet spectrophotometry, infrared spectrophotometry and amino acid composition analysis showed that the total amount of amino acids in ginseng alcohol soluble protein was 82.3 g/100 g, of which the content of essential amino acids was 26.46 g/100 g, and the content of medicinal amino acids was 30.51 g/100 g, which verified that the main component of ginseng alcohol extract was indeed protein, and the molecular weight was about 3.3 kDa. The SEM results showed that the ginseng alcoholic protein was structurally complete, the surface was sparse with irregular ridges and a small number of pores, and the protein particles showed honeycomb aggregation with a stable and orderly reticular structure. The results of in vitro antioxidant test showed that the protein had strong in vitro antioxidant activity under strong acidic conditions. When the pH was 1, the scavenging rate of ginseng alcohol soluble protein for DPPH radical was 96%, the scavenging rate for ·OH was 79%, and the reducing ability for iron ion was 0.86.