Water-in-oil soybean concentrated phospholipids hydrolysis based on the model of enzymatic deactivation and its application in bread

Abstract Soybean phospholipids and their enzymatic hydrolysates are commonly used emulsifiers. However, hydrolysis of soybean phospholipids by low-cost phospholipase A1 (PLA1) in a water-in-oil (W/O) system can be affected by enzymatic deactivation and excessive hydrolysis. Thus, establishing a mechanical model is necessary. In this study, the maximum acid value reaction parameters were first selected by the orthogonal optimization method: 1.5% of PLA1 with 25% of water at 60 °C, and the highest acid value of the hydrolysates was 121 mg • KOH/g. The physicochemical properties of PLA1 and PLA2 hydrolysates were compared under different optimal hydrolysis conditions at different times using starch complexing index, surface tension, emulsifying properties, and foaming properties as indicators. The results showed that the optimum indexes of the indicators were obtained at 0.75 h with the acid value of 70.3 mg • KOH/g. A reaction model for the hydrolysis of soybean phospholipids by PLA1 was established to control the hydrolyzed phospholipid quality at other conditions. The model of fatty acid concentration, reaction time, and enzyme content at 60 °C and 15% water were obtained by fitting with the first- and second-order enzyme deactivation models. The predicted and experimental values showed the following relationship: [P] = [S] × {1 − [1 + (143.55[E])/(74.38 + [E])]tˆ(−0.0897)}. The PLA1-and PLA2-hydrolyzed phospholipids for 0.75 h with the optimum indexes of the indicators were selected to make bread, which helped improve the bread volume and reduce the crumb hardness and staling rate successfully.