Buckwheat hull, a valuable bakery product ingredient: assessment of bioaccessible phenolics and antioxidant capacity

In this study, the bioaccessible total phenolic compounds (TPC) and antioxidant capacity (AC) of commonly consumed bakery products enriched with raw (BH) or roasted (RBH) buckwheat hull were evaluated. The soluble and insoluble fractions obtained after in vitro enzymatic digestion of mixed rye/wheat bread with 4% of RBH (BRBH), wheat bread with 3% of BH (BBH), and their control counterparts were separated (C-BRBH and C-BBH, respectively). The addition of buckwheat hull, raw and roasted, significantly increased the values of analyzed parameters compared to control samples. Before the digestion, the highest values of TPC and AC were found for bread with 4% of RBH. After in vitro digestion of the bakery products, the content of TPC and AC in the soluble fraction was 75-90% higher compared to the values found in the undigested fraction. Generally, a decrease in the bioaccessibility index of enriched bakery products compared to control samples was observed. The obtained results indicate that buckwheat by-products may be used as a valuable ingredient for commonly used bakery products. Also, it was shown that the in vitro digestion model may be of relevance in assessing the bioaccessibility of bioactive compounds in commonly used bakery products.