In vitro Digestibility Profiles of Different Types of Resistant Starch With Bioactive Guest Inhibitors

Abstract

Abstract Objectives Retardation of starch digestion is an effective way of optimizing glycemic response. As the non-digestible portion of starch, resistant starch (RS) is associated with several beneficial effects such as regulating blood glucose level and improving gut health. Although all types of RS demonstrate such health benefits, different subtypes and structures may lead to variations in the digestibility profile. The aim of this study was to investigate and compare the in vitro digestibility of type 2 RS (RS2), type 3 RS (RS3), and novel type 5 RS (RS5) produced by starch inclusion complexes with ascorbyl palmitate (AP) and palmitic acid (PA) as potential inhibitors or guest compounds. Methods Two RS2 samples (high amylose maize starch, HAMS; potato starch, PS) in both raw and cooked forms, and RS3 samples produced by retrogradation of the two starches were tested for in vitro enzymatic digestion. AP and PA were either added during the digestion of RS2 and RS3 samples as potential inhibitors or processed to form inclusion complexes with starch prior to digestion as guest compounds of RS5. Starch digestibility profiles, represented by rapidly digestible starch (RDS), slowly digestible starch (SDS), total digestible starch (TDS), and RS contents, were determined. Results Cooking significantly increased the digestibility of RS2, while retrogradation (formation of RS3) inhibited the digestion by increasing the SDS and RS contents. The addition of AP significantly inhibited the in vitro digestion of RS2 (both raw and cooked HAMS and PS) and RS3 (retrograded HAMS and PS). The digestibility profile of RS5 produced by forming starch inclusion complexes with AP and PA was comparable to that of RS3, which exhibited higher SDS and RS contents as compared to cooked RS2. Conclusions AP as a bioactive guest compound could inhibit the in vitro digestion of raw and cooked RS2 and RS3. RS5 produced by forming starch inclusion complexes with AP and PA presented comparable digestibility with RS3, and higher SDS and RS contents as compared to cooked RS2. Since raw RS2 is not normally consumed in daily life, RS3 and RS5 could serve as better choices for daily consumption. In addition, adding certain bioactive food components could compensate for RS loss, suggesting a practical way of modulating glycemic response. Funding Sources University of Alabama Emerging Scholar Program and Faculty Start-up Fund.