Thermoplastic extrusion technology as a tool for adding value to brewer's by-products

Brewer's by-products show high nutritious potential to be reintegrated into the food chain. Nevertheless, their high moisture, microbiological instability, and heterogeneity pose enormous challenges. This study investigated thermoplastic extrusion to repurpose large amounts of the two main brewery by-products: brewer's spent grains (BSG) and brewer's spent yeast (BSY). A mixture design was used to compose ten blends with different proportions of dried-BSG, BSY, and corn grits, maximizing the use of BSG up to 70 g/100 g. Extruder parameters were fixed. PLS regression was applied to evaluate the effects of blend composition on the characteristics of the extruded products. Thermoplastic extrusion shows feasibility in transforming large volumes of by-products into value-added products. Blends with high insoluble fiber, protein, and moisture contents resulted in extrudates with high protein concentration, low expansion, and high density. The results of this exploratory work can be used for product optimization by choosing nutritional, technological, and commercial targets to create innovative, healthy, and sustainable food products that meet consumer demands.