Effects of Grape Seed Proanthocyanidins and Malic Acid on Digestive Characteristics of Starch in Bread

The effects of grape-seed proanthocyanidins (GSP) and malic acid (MA) on the multiscale structure and digestibility of starch in a bread model were investigated. Fourier transform infrared (FTIR), Raman spectroscopy analyses, long-range order (crystallinity), amylolytic release of glucose, as well as the effect on α-amylase activity of starch in the bread, were determined. The combination of GSP and MA increased the molecular order but decreased the crystallinity of the starch. Amylase fluorescence spectra showed that the α-amylase was notably quenchable by adding GSP and MA, and the inhibition rate of α-amylase reached 10.3%. Confocal Laser Scanning Microscopy (CLSM) imaging confirmed the digestion data in vitro showing that in the presence of 0.3% GSP and 0.5% MA in the bread, the glucose release of the bread was reduced to 5.43%. These findings demonstrate that GSP and MA can effectively modulate starch structure and digestibility in bread, offering a strategy to control glucose release in baked foods.