Effect of buckwheat bran enrichment on wheat dough and bread properties

The production of foods rich in dietary fiber represents one of the most important driving forces in the development of innovative cereal-based products. However, inclusion of high levels of fiber 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%), with different particle size (dav bran as such: 360 μm; dav micronized bran: 110 μm). Dynamic Mechanical Thermal Analysis (DMTA) and differential scanning calorimetry (DSC) allowed evaluating the effects of bran on the thermo-mechanical transition during processing. Dough rheology at large deformations was assessed by the Kieffer test. Standard baking tests and texture profile analysis were performed on bread in small-scale trials (60g puffy loafs). As for the dough properties, both DMTA and DSC approaches indicated that bran enrichment resulted in a progressive increase in the onset temperature of starch gelatinization. DMTA also provided evidence as for changes in the viscoelastic behavior during heating associated with bran enrichment. As for the dough behavior at large deformations, dough resistance to extension decreased with increasing bran inclusion. On the contrary, no univocal behavior was assessed as for the dough extensibility increase. As for baking quality, the decrease in loaf volume due to buckwheat bran enrichment clearly depended on the level of inclusion and on bran particle size. Crumb moisture content of fresh bread reflected the behavior in dough water absorption for both types of bran: gradual enrichment with buckwheat as such led to a wet product, whereas the substitution level with micronized bran has no significant effect. Crumb firmness increased as the bran content increased and was positively correlated with the increase in crumb density. For this reason, the Ahsby-Gibson theory for cellular solid foods was applied. Bran as such increased the corrected hardness for addition level higher than 10%. On the contrary, the addition of micronized bran deeply altered crumb firmness already at 5%. The inclusion of 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.