Effects of Pretreatment on the Yield of Peanut Oil and Protein Extracted by Aqueous Enzymatic Extraction and the Characteristics of the Emulsion.

Effects of comminution on peanut particle size and yield of peanut oil and protein were analyzed. Additionally, the emulsion properties (surface protein concentration, particle size, and ξ-potential) were compared. Moreover, different demulsification methods were used to investigate the emulsion stability. Results showed that the yield of peanut oil and protein was highest (87.23% and 82.05%, respectively) after dry comminution for 72 s. Upon wet comminution for 120 s, the yields of peanut oil and protein were 89.91% and 84.70%, respectively, which were both significantly higher than that obtained after dry comminution (p < 0.05). The surface protein concentration and ξ-potential of emulsion made by dry comminution (DCE) were 7.02 mg/m and 12.08 mV, respectively, and those of emulsion made by wet comminution (WCE) were 10.71 mg/m and 15.25 mV, respectively, which were significantly higher than that of DCE (p < 0.05). The volume average particle size of DCE was 3.41 µm, which was significantly higher than that of WCE (3.18 µm, p < 0.05). Collectively, these results indicated that WCE was more stable than DCE. Further, the demulsification rate of DCE was significantly higher than that of WCE when treated by freeze-thawing, pH, papain, and phospholipase A2 (p < 0.05). Demulsification effect of Alcalase 2.4L was the best among these five demulsification methods treated, and the demulsification rate of DCE reached 92.77%, which was slightly higher than that of WCE (92.67%), further illustrating the higher stability of WCE.