Effect of enzymatic hydrolysis of brewer’s spent grain on bioactivity, techno-functional properties and nutritional value when added to a bread formulation.

The interesting nutritional value and abundance of brewer´s spent grain (BSG) may be adequate for its use as a sustainable functional ingredient. The aim of the present work was to enhance BSG bioactive properties, along with studying the BSG bread technological feasibility by rheological properties evaluation. To optimize the release of BSG bioactive compounds, an enzymatic hydrolysis was carried out using a composite central design, varying alcalase and cellulase percentage. Multiple regression (MR) and response surface methodology (MSR) were performed evaluating total polyphenol content (TPC), ABTS and ORAC as response variables, showing a positive effect for alcalase % and non-significant for cellulase %. The optimal conditions (0.1% alcalase) was used as BSG flour (FBSG) for the development of the functional bread (BBSG), substituting 20% w/w of wheat flour. The nutritional and bioactive characterization of the breads showed BBSG presented higher fiber content (>6%), TPC and antioxidant activity than control bread (CB). Breads’ physicochemical characteristics were analyzed by measuring the parameters of volume, color and texture. Regarding volume, BBSG presented a significant decrease (p<0.05) (1890.4±6.9 cm³) with respect to CB (2359.5±106.5 cm³), and also presented a significant increase (p <0.05) in the development of brown/reddish tones in the crumb, which reflected in L and a parameters (53.62 and 6.10 respectively) compared to CB (75.70 and -0.16 respectively). Texture analysis showed BBSG chewiness (6.85±0.13 Kg) and cohesiveness (0.608±0.027) did not present significant differences (p>0.05) with CB. On the other hand, the BBSG parameters of resilience (27.5±2.3), and rubberiness (7.63±0.16 Kg.m.s^-2) were increased while elasticity (89.81±0.067) decreased. In conclusion, a sustainable "high fiber content" and antioxidant bread was obtained presenting suitable rheological properties as wheat flour bread. Further studies on sensory profile and acceptability of the novel food should be addressed in order to evaluate the consumers' perception on rheological parameters.