Insight into the presence state and stability mechanism of oil in aqueous system during aqueous enzymatic extraction of peanut oil and protein simultaneously

This study aimed to examine the presence state and stability mechanism of oil in aqueous system (AS) during aqueous enzymatic method. The AS comprised oils in three states: free-state oil (FSO), emulsified-state oil (ESO), adsorbed-state oil (ASO). The contents of residual oil were the lowest in AS (9.07%), while those of ESO, ASO, and FSO were 5.88%, 1.62%, and 1.57%, respectively, under the following conditions: crushing pretreatment, 120 s; enzyme concentration, 1.5%; hydrolysis temperature and time, 50 °C and 1.5 h; pH, 7.0. Stability mechanism of oil in AS was elucidated by examining protein interfacial behaviour, secondary and spatial structure, intermolecular interactions. ASO was existed through the exposure of intramolecular hydrophobic groups in specific proteins. Protein aggregates with reduced interfacial tension and attenuated hydrogen bonds stabilised ESO by anchoring at the oil-water interfaces. Protein-induced viscosity modulation in AS maintained colloidal stability of small oil particles, facilitating the formation of FSO. • Oil in AS was lowest when extraction under enzyme 1.5%, 50 °C, 1.5 h, and pH 7.0. • Three state oils (FSO, ESO, ASO) were presented in aqueous phase systems (AS). • Hydrophobic sites of specific protein’s hydrophobic groups adsorbed oil to form ASO. • ESO existed by anchoring at interface of protein with interfacial tension and -H. • FSO existed by AS viscosity modulation induced by proteins.