Glycaemic index (GI) suppression of bread using polyphenols enriched <i>karonda</i> powder: a strategy to reduce starch digestibility and increase polyphenols retention

Abstract The present study aims to develop polyphenol-enriched low GI bread using phytochemical rich karonda powder. The refined wheat flour was supplemented with ripe karonda powder (RKP) at 1.5 %, 3.0 %, 4.0 %, and 6.0 % level. The prepared formulations were evaluated for their chemical, physical, texture, sensory properties and starch digestibility. Properties like loaf height, specific volume, and bake loss decreased with increase in RKP incorporation. Specifically, loaf height and volume reduced from 8.07 cm and 562 cc (control) to 5.52 cm and 355.67 cc at 6 % RKP incorporation. Total phenolic content increased from 25.56 mg GAE/100 g in control bread to 66.94 mg GAE/100 g at 6 % RKP incorporation, showing a 162 % increase. Antioxidant activity, measured by DPPH inhibition, increased from 12.16 % in control bread to 21.91 % in 6 % RKP-enriched bread. Texture analysis indicated that as the concentration of RKP increased, the bread exhibited increased hardness due to the dilution of the gluten network. Additionally, incorporating RKP increased the redness (a*) and reduced the lightness (L*) value in bread, attributable to the anthocyanin content in RKP. Sensory evaluation results suggested that bread containing 3 % RKP was the most acceptable, with flavour and texture scores comparable to the control. Furthermore, in vitro starch digestibility and predicted glycemic index (pGI) analysis revealed that incorporating RKP at 1.5 % and 3.0 % significantly lowered the pGI by 10.63 % and 20 %, respectively, compared to control bread. This study will be helpful for diabetic patients to manage their blood glucose levels by incorporating polyphenols in their diet.