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

Authors: Thai, Thanh Thao S; Avena-Bustillos, Roberto; ALVES, PRISCILA - Non ARS Employee; Pan, James; OSORIO-RUIZ, ALEX - Instituto Politécnico Nacional, Centro De Desarrollo De Productos Bioticos (CEPROBI); Miller, Jacklyn; Tam, Christina; ROLSTON, MATTHEW - University Of California, Davis; TERAN-CABANILLAS, ELI - Autonomous University Of Sinaloa; Yokoyama, Wallace - Wally; McHugh, Tara

Submitted to: Applied Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2022
Publication Date: 2/2/2022
Citation: Thai, T.T., Avena Bustillos, R.D., Alves, P., Pan, J., Osorio-Ruiz, A., Miller, J.D., Tam, C.C., Rolston, M.R., Teran-Cabanillas, E., Yokoyama, W.H., McHugh, T.H. 2022. Influence of drying methods on health indicators of brewers spent grain for potential upcycling into food products. Applied Food Research. 2(1). Article 100052. https://doi.org/10.1016/j.afres.2022.100052.
DOI: https://doi.org/10.1016/j.afres.2022.100052

Interpretive Summary: Brewer’s spent grain (BSG) is the most abundant by-product of beer brewing and is a low-cost by-product with potential for use in value-added applications, such as energy, biotechnology, and food. Successful commercial products incorporating BSG in nutritional bars, savory puffed snacks and other innovative foods had been developed by ReGrained Inc., our industrial partner. The dense concentration of nutrients in addition to its low cost and large volume availability, make BSG a desirable potential value-added waste product. However, owing to its high moisture as a fresh by-product, BSG must be preserved to extend its shelf-life and reduce transportation and storage costs. Currently, methods of preservation of BSG include freeze-drying, freezing, oven-drying, and superheated steaming, with the most common being rotary drum-drying. These methods utilize large amounts of energy, so energy-efficient alternatives need to be sought. Hot air drying (HAD) utilizes high temperatures of air to blow across trays of samples. Another form of drying is infrared drying (IRD), which was patented by our group through a collaboration with ReGrained, Inc. as industrial partner, involving heating with infrared irradiation that requires less time and less energy than hot-air drying while achieving a safe water activity, crispy texture, and roasted aroma. In the current study, BSG was dried via IRD and HAD, and proximate analysis was performed for characterization. A mice-feeding study, in which BSG dried by the two drying methods and each incorporated into the diets at three concentration levels, was conducted to determine potential health benefits of BSG.

Technical Abstract: 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. No significant differences in health indicators of mice fed BSG dried by the two different BSG drying processes were observed. Significant differences (p < 0.05) were observed for liver and adipose tissues, cholesterol, and fecal protein between mice fed diets with different concentrations of BSG. The analysis of hormones related to type II diabetes and metabolic syndrome did not show difference between the hormones examined except for ghrelin and leptin, which are directly correlated with increased white adipose tissue in mice consuming high fat diets. Mice fed with HAD and IRD BSG diets increased relative abundance of Firmicutes and Bacteriodates phylum microbiota compared to the control diet with no differences due to the type and concentrations of BSG in mice diets. Results from this study suggest increasing levels of BSG incorporated into human foods may impart health benefits.