Synergistic impact on postprandial glycemic response to whole grain fonio flour (Digitaria iburua) by its particle size and released phenolic compounds

Abstract

Cell wall-sourced dietary fiber and phenolic compounds (PC) are essential in imparting the health advantages linked to whole grain foods (WGFs), but their interaction in a whole grain context is not fully understood. This research explored the influence of phenolic compounds and particle size on the digestion of starch in the black fonio variety. The results highlighted the importance of maintaining cell wall integrity for efficient starch digestion, revealing that the starch digestion rate and extent decreased with increasing particle size. The rapidly digestible starch (RDS) from mill 1 (M1) and mill 2 (M2) demonstrated significant increases, attributed to the reduced availability of liberated phenolic compounds during digestion, with values of 78.08 % and 69.94 %, respectively. Meanwhile, the starch bioaccessibility were higher in the dephenolized flour (M1 and M2: 54.50 and 26.23 % respectively) than in the native (M1 and M2: 30.99 and 21.39 % respectively). The in vivo study on postprandial glycemic response (PGR) to Fonio flour showed a similar trend with in vitro starch digestion. Generalized linear modelling (GLM) revealed a synergistic interaction between released PC and particle size in modulating starch digestion (P < 0.05) and glycemic index (GI) (P < 0.01). Thus, the WGFs processing to produce appropriate flour particle size is an efficient way to maximize the health benefits of WGFs.