Investigation Of Resistant Starch Content And Glycemic Index Of Bread Supplemented With Modified Sweet Potato Starch

Abstract

Resistant starch was known as a small fraction of starch which is resistant to the hydrolysis in vitro. RS is fermented by micro-flora in large intestine, thus bringing health benefits for human. The objective of this study is to investigate level of resistant starch and glycemic index as well as producing low-carb bread which was supplemented with high resistant starch from sweet potato starches. The native sweet potato starches isolated from sweet potatoes in MeKong delta were physically modified. The sweet potato starches after modification using acid heat-moisture treatment (A-HMT) were subjected to investigate the level of resistant starch (RS) and the glucose tolerance in mice. Three kinds of bread were made from 100% wheat flour as the control sample, 20% sweet potato starch and 20% physically modified sweet potato starch by acid heat-moisture treatment. The starch fractions including rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) were determined before, after starch modifications and bread making. The RS content of native starch was 23.38%. The RS content of sweet potato starches increased to 40.46% after applying A-HMT. After supplementing 20% modified starch for making bread, the resistant starch (RS) content was 34.16%.Moreover, the glycemic index (GI) of native starch, modified starch, bread 100% wheat flour, bread supplemented with 20% native starch and bread supplemented with 20% modified starch were 120.5, 97.9, 100, 94, 68.9 respectively. The modified sweet potato starches reduced the GI value compared with the native starches. The bread supplemented with modified sweet potato starches were significantly reduced the GI values. As a result, bread supplemented with modified starch was considered as a low-carbohydrate food which brings many benefits for human. Key words: Sweet potato starch, resistant starch, glycemic index, modified starch