Fortifying bread rolls with date fruit fiber: Effects on dietary fiber, antioxidant capacity, mineral content, and glycemic response

Abstract

This study explored the effects of fortifying bread rolls with desugared date fruit pomace on their nutritional value. Bread rolls containing 0, 5, 10, 15, and 20 % date fruit pomace were analyzed for macro- and micronutrients, dietary fiber, phenolic content, and in vitro digestibility. In contrast, three variations (0, 10, and 20 %) were tested for their effect on the glycemic index. Fortification with date fruit pomace significantly increased the total dietary fiber content of the bread, from 5.7 g/100 g in the control to 22.4 g/100 g in the 20 % breads (P < 0.001). Antioxidant activity, indicated by FRAP, rose from 8.2 to 11.1 μmol Trolox equivalents (TE)/g. Similarly, hydrolysable phenolic activity, assessed through both FRAP and DPPH assays, showed an increase with fortification. In vitro digestibility analysis revealed that date pomace fortification progressively reduced glucose release during the oral, gastric, and intestinal digestive phases, with the most significant reduction observed in the oral and gastric phase for the 10 % bread. This effect could result from enzyme inhibition caused by components in date pomace, especially phenolics. Glycemic index testing with eight healthy participants revealed GI values of 93 and 85 for the 10 % and 20 % pomace breads. These results suggest that while desugared date fruit pomace improves the nutritional and antioxidant profile of bread rolls, it has a minimal effect on reducing the glycemic response.