Influence of drying methods on health indicators of brewers spent grain for potential upcycling into food products

Brewer's spent grain (BSG) was dried via infra-red drying (IRD) or hot-air drying (HAD) and milled into fine powders. Proximate analysis (moisture, protein, fat, ash, carbohydrates by difference), water activity, dietary fiber, total soluble phenolics, and antioxidant capacity analyses were performed to characterize and compare both types of BSG powders. Mice feeding of the two types of dried BSG, each at three different concentrations, was conducted to compare the effects of the two types of dried BSG on health indicators and to determine evidence of dose response. Weights of body, feed intake, adipose tissue, kidney, and liver were recorded; blood plasma, cholesterol, liver fat, and fecal fat and protein were also measured. Significant differences were observed for liver and adipose tissue, cholesterol, and fecal protein between mice fed diets with different concentrations of BSG compared to the control diet. The analysis of hormones related to type II diabetes and metabolic syndrome did not show differences between the hormones examined, except for ghrelin and leptin, which are directly correlated with increased white adipose tissue in mice consuming high fat diets. No differences in health indicators were found in mice fed with the two different types of BSG. Mice fed with HAD and IRD BSG diets increased the relative abundance of Firmicutes and Bacteroidetes phylum microbiota compared to control diet, with no differences due to the type and concentrations of BSG in mice diets. The present results suggest that increasing levels of BSG incorporated into human foods may impart health benefits.