Flours from microwave-treated buckwheat grains improve the physical properties and nutritional quality of gluten-free bread

Microwave (MW)-assisted hydrothermal treatment of buckwheat grains was explored to improve the physical properties and nutritional quality of gluten-free (GF) bread. A mixture of 80% rice flour and 20% corn starch was used as control recipe (CR), whereas for fortification, 50% of the rice flour was replaced with native buckwheat flour (BN) or buckwheat flour from grains treated with several MW cycles (exposure/rest cycles of 10/50 s, BT1, 20/40 s, BT2, or 30/30 s, BT3, at 30% moisture content and 8 min MW exposure). The BN fortified dough showed increased consistency and elastic response, compared to CR, with the MW treatment further enhancing these effects. Due to the enormous increase in complex modulus (G1*) (from 1060 Pa for CR to 10,679 Pa for BT3), the hydration of doughs was subsequently adjusted to obtain similar G1*. The inclusion of MW-treated flours led to higher consistency and elastic recovery. The lower specific volume (SV) and higher crumb hardness encountered for BN (3.88 mL/g and 1.45 N) were alleviated by the inclusion of MW-treated flours (4.61 mL/ g and 0.90 N for BT1, 4.39 mL/g and 0.85 N for BT3), resulting in similar SV and lower staling than CR. Moreover, compared to BN and CR, the BT2 and BT3 breads showed a significant reduction in glucose release during in vitro starch digestion (up to -25%), and an increase in protein digestibility (up to +23%). Overall, the experimental findings pointed to the feasibility of using MW to improve the physical and nutritional quality of buckwheat flour-enriched GF bread.