Effect of enzyme on the demulsification of emulsion during aqueous enzymatic extraction and the corresponding mechanism

Backgrounds and objectives Emulsion is formed during the aqueous enzymatic extraction (AEE) of peanut oil and protein. Protein and phospholipid, the main emulsifiers, play an important role in the stability of this emulsion. In this study, phospholipase A1, phospholipase A2, phospholipase D, papain, or Alcalase 2.4 L was used as demulsification agents. The phospholipid composition, interfacial protein concentration and composition, viscosity, particle diameter distribution, and microstructure of the emulsion during demulsification were evaluated. Findings Nuclear magnetic resonance analysis showed that the content of phosphatidylcholine decreased by 12.3% after treatment with the three phospholipases, whereas the content of phosphatidic acid increased 9 times. Treatment with protease caused the molecular weight of interfacial proteins and the viscosity of the emulsion significantly decreased, and the average particle diameter increased 8 times. Conclusions The free oil yields obtained using PLA1, PLA1/PLA2, PLD, Alcalase 2.4 L, and papain were 45.6%, 85.3%, 30.7%, 84.3%, and 93.8%, respectively. Papain destroyed the interfacial membrane of the emulsion and had the best demulsification effect. Significance and novelty The findings solve the problem of difficult demulsification during the extraction of peanut oil by AEE and provide a theoretical basis for the large-scale industrial application of the demonstrated demulsification method.