Combined Effect of Sorghum and Barley Flours Incorporation on invitro Starch Digestibility, Estimated Glycemic Index and Consumer Acceptability of White Bread

Abstract

Excess consumption of white bread has been linked towards the development of diabetes mellitus because of its high starch digestibility. Previous studies suggested that the addition of other grains, legumes and medicinal herbs to bread might reduce its starch digestibility. However, the incorporation of these nonwheat materials into bread is challenging from consumer acceptability perspective. Therefore, the current study investigated the effect of incorporating red sorghum and barley flours in white bread on in-vitro starch digestibility, estimated glycemic index (eGI) and consumer acceptability. Bread was formulated by incorporating blends (equal proportion) of sorghum and barely flours at 20%, 30%, 40% and 50% levels, each. Composite bread was compared with control bread (CB) made from 100% wheat flour only. In-vitro starch hydrolysis was determined enzymatically at 0, 20, 30, 45, 90 and 120 min. Rapidly digestible starch (RDS), slowly digestible starch (SDS), resistant starch (RS) and estimated eGI were calculated from starch digestion values. Consumer acceptability was determined using nine-point hedonic scale. The incorporation of sorghum and barley into wheat bread decreased in-vitro starch digestion at all incorporation levels than CB. RDS content significantly (P < 0.05) reduced in 40% and 50% sorghum and barley-containing bread (SBB), respectively, compared to CB. The eGI of SBB, at all incorporation levels, was significantly (P < 0.05) lowered compared to CB. Consumer sensory evaluation revealed that bread containing sorghum and barley flour, up to 40% level, was acceptable based on pre-set acceptability criteria. In conclusion, incorporation of sorghum and barley flour to white bread at 40% level is possible to decrease its digestibility and glycemic index, whilst maintaining consumer acceptability.