In vitro gastrointestinal digestibility of native, hydroxypropylated and cross-linked wheat starches

The digestibility and estimated glycemic indices (GI) of native (NWS), cross-linked (CLWS) and hydroxy-propylated wheat starches (HPWS) were obtained by in vitro enzymatic hydrolysis. The resistant starch (RS) content and GI were found to be 6.59 and 93.13 for NWS, 7.57 and 92.20 for CLWS, and 13.15 and 89.04 for HPWS, respectively. The amounts of glucose release for CLWS were approximately 6-11%, and for HPWS were 16-19%, lower than that for NWS after digestion under simulated intestinal conditions (SIC). The linear and two-term exponential models were fitted well to the experimental glucose release data under simulated gastric conditions (SGC) and SIC, respectively (R-2 = 0.858-0.991). After digestion under SIC, the consistency coefficient (k) values drastically decreased (73.02-90.27%), while the flow behavior index (n) increased (155.56-363.64%). Therefore, the amounts of glucose release can be controlled by manipulating the structure of native starches using chemical modifications such as cross-linking and hydroxypropylation.