Including buckwheat bran in wheat dough and bread: what happens?

Development of products rich in ingredients with high nutritional value –as dietary fiber– is currently one of the most important goals for food companies. However, inclusion of high levels of fiber in cereal-based products is still technologically challenging, as for the texture and the sensory quality. Buckwheat is a nutritionally-relevant pseudo-cereal and is traditionally used in Europe and Asia for pasta production, but rarely exploited in bakery applications. In this study, we investigated the effects of enriching wheat flour with increasing levels of buckwheat bran (5, 10, 20%), before and after micronization. DMTA and DSC allowed evaluating the effects of bran on the thermo-mechanical transition during processing while dough rheology at large deformations was assessed by the Kieffer test. Standard baking tests and TPA were performed on bread. Regarding dough properties, both DMTA and DSC showed that bran enrichment resulted in increase in the temperature of starch gelatinization. The size of the effect depended on bran amount and particle size. DMTA also provided evidence as for changes in the viscoelastic behavior during heating. As for Kieffer test results, increasing bran inclusion led to a decrease of resistance to extension. Concerning the baking quality, the decrease in loaf volume due to buckwheat enrichment clearly depended on the level of inclusion and on bran particle size. Moisture content of fresh bread reflected the behavior in dough hydration for both types of bran: gradual enrichment with buckwheat as such led to a more wet product, whereas the substitution level with micronized bran had no significant effect. Crumb firmness increased as the bran content increased and was positively correlated with crumb density. The Ahsby-Gibson theory for cellular solid was applied to correct for the effect of density. Bran as such increased the corrected hardness for addition level higher than 10%. On the contrary, micronized bran deeply altered crumb firmness already at 5% substitution level. Overall, buckwheat bran greatly affected dough rheology and thermal transitions during baking, which resulted in considerable changes in bread quality. Such changes could be related not only to the enrichment degree but also to the size of the bran particles.