Effect of ultrasonic pretreatment on physicochemical characteristics and rheological properties of soy protein/sugar Maillard reaction products

Maillard reaction products (MRPs) of soybean protein isolate (SPI) and sugars (glucose andmaltose) were prepared by heating in the aqueous dispersion at 95 degrees C for 15 min with ultrasonic pretreatment (ultrasonic power of 200W) for 20 min. Effect of ultrasonic pretreatment on physicochemical characteristics and rheological properties of SPI/sugar MRPs was investigated. SPI/sugar MRPs prepared with ultrasonic pretreatment had higher degree of glycation (DG), lower browning and less compact tertiary conformation than that with non-ultrasonic pretreatment. Surface hydrophobicity (H-0), particle size and rheological properties were measured by fluorescence spectrophotometry, laser particle size analysis and dynamic oscillatory rheometry, respectively. Glycation reduced H-0 and particle size as well as weaken the gel network formed by the acidification of GDL. However, ultrasound increased H-0 and decreased particle size. This is desirable for the formation of acid-induced gel structure. The ultrasonic pretreatments reduced/eliminate the weakening effect of glycation on the gel network of SPI/sugar MRPs, and even improved the gel properties.