Limited enzymatic hydrolysis of soy protein enhances cholesterol absorption inhibition in Caco-2 cells.

Protein hydrolysates were produced by hydrolyzing isolated soy protein (ISP) with enzymes including flavourzyme, alcalase, trypsin, chymotrypsin and pepsin for 12 h, respectively. Each hydrolysate was measured its recovery and evaluated its relative cholesterol uptake (RCU, %) in Caco-2 cells. The higher the recovery represented the higher the yield. The lower the RCU revealed the higher the cholesterol absorption inhibition. The result indicated that intact ISP could further decrease its RCU by hydrolyzing with any of these enzymes. Flavourzyme-ISP hydrolysate had the lowest RCU of 37% and maintained the highest recovery of 58% than the others. The effects of limited ISP hydrolysis using flavourzyme in terms of the degree of hydrolysis (DH, %) on recovery and RCU in Caco-2 cells were also investigated. When the DH was less than 22.8%, the RCU decreased with the increase in DH. However, extensive ISP hydrolysis using flavourzyme to obtain DH higher than 28% did not guarantee enhance the cholesterol absorption inhibition but significantly (p＜0.05) decreased the recovery. According to micelle inspection using a transmission electron microscope, the hydrolysate was clearly incorporated into the micellar membrane but ISP wasn't. This finding suggested that incorporation of the hydrolysate lead to reduce cholesterol solubility during micelle preparation as well as inhibit cholesterol absorption in Caco-2 cells.