Effect of Ultrasonic Treatment on Soybean Oil: Focus on Degumming of Soybean Crude Oil and the Quality of Degummed Oil

This study investigated the effect of ultrasonic-assisted degumming technology on the degumming of soybean crude oil, and the quality change of degummed oil was analyzed. The response surface method designed by Box–Behnken was used to optimize the degumming process conditions. Under the optimal conditions of water addition of 6 mL/100 g, ultrasonic temperature of 45°C, ultrasonic time of 10 min, and ultrasonic power of 60 W, the degumming rate was 73.82%, which was 21.69% higher than that of hydration degumming (52.13%). The phosphorus content of ultrasound-assisted hydration degummed oil (31.21 mg/kg) was significantly lower than that of hydration degummed oil (57.08 mg/kg) and soybean crude oil (119.23 mg/kg). The phospholipid composition and content of degummed oil (phosphatidic acid [PA]: 2.00 mg/g) were lower than that of the hydrated degummed oil (phosphatidylethanolamine [PE]: 0.93 mg/g; PA: 2.28 mg/g) and soybean crude oil (phosphatidylcholine: 9.50 mg/g, PE: 7.28 mg/g, phosphatidylinositol: 7.13 mg/g, and PA: 3.41 mg/g). The results showed that ultrasonic-assisted degumming could significantly reduce the acid value of oil (1.60 mg/g) and slightly reduce the iodine value (130 g/100 g). Moreover, the oxidation stability of the oil was slightly improved. In addition, ultrasonic-assisted hydration degumming could improve the color of oil and slightly reduce the content of unsaturated fatty acids (UFAs) in soybean oil. Aldehydes, alcohols, and acids were identified as the main volatile flavor components for the degummed oil. Therefore, the ultrasonic-assisted hydration method can improve the degumming effect and soybean oil quality.

Practical Applications: Response surface methodology was used to optimize the ultrasonic-assisted degumming process of soybean crude oil. Compared with hydration degumming, ultrasonic-assisted hydration degumming improved degumming effect, reduced phospholipid content, made soybean oil clear and bright, weakened the flavor of natural oils such as crude oil and nuts, and improved the oxidation stability of oil. Moreover, ultrasonic-assisted hydration degumming could slightly reduce the content of UFAs in soybean oil. At the industrial level, the introduction of ultrasonic technology in one step of the application process is a green processing technology, which is conducive to the production of high-quality refined oil.