Feasibility of Extruded Brewer’s Spent Grain as a Food Ingredient for a Healthy, Safe, and Sustainable Human Diet

Abstract

This study aimed to determine the effect of the extrusion process on the nutritional and bioactive profiles of brewer’s spent grain (BSG), contributing to nutrition security by applying a circular economy concept. Response surface methodology was used to optimize the effect extrusion parameters (moisture content, screw speed, and barrel temperature ) had on BSG’s soluble dietary fiber, free glucose, and overall antioxidant capacity. Proximate composition analyses, amino acid profile, extractable polyphenolic content, and antioxidant capacity of BSG and brewer’s spent grain extruded under optimal conditions (BSGE) were carried out. Food safety was analyzed by their microbiological quality, gluten, and acrylamide content. Optimal extrusion conditions were 15.8% of moisture content, 164.3 revolutions per min and 122.5 °C. BSGE presented 61% more soluble dietary fiber than BSG, lower digestible starch, 0.546% of free glucose, and protein quality parameters mostly like those reported for egg, soy, and milk. Despite this, BSG’s overall antioxidant capacity was not improved after thermomechanical processing; BSGE had significantly higher extractable polyphenolic content in its alkali extracts, which were determined qualitatively by high-performance liquid chromatography quadrupole time-of-flight assay in its hydro-alcoholic acid extracts. Furthermore, although it is not gluten free, BSGE is a safe food ingredient with acceptable microbiological quality and no acrylamide.

Optimisation of alkaline extraction of protein from brewer’s spent grain

“…Consequently, alkaline extraction of micronised BSG may generate protein isolates rich in glutamate, proline and aspartate but may not be an ideal source of methionine. Moreover, the amino acid composition reported here is consistent with the previous studies presented in Table 1 (Gmoser et al, 2020; Gutiérrez‐Barrutia et al, 2022; Oluseyi et al, 2011; Waters et al, 2012; Yu et al, 2020). Due to its thermal instability, tryptophan is susceptible to breakdown when exposed to high temperatures (Cuq et al, 1983) and therefore lost in the hydrolysis conditions used for amino acid analysis.…”

“… ‡ Amino acid composition of BSG from previous studies, presented as a range of the values reported by Gmoser et al (2020), Gutiérrez‐Barrutia et al (2022), Oluseyi et al (2011), Waters et al (2012) and Yu et al (2020). …”

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

“…BSG was utilized as an ingredient during extrusion processing to produce puffed snacks, pasta, breakfast cereals, different nutritional ingredients, and bread [ 8 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ].…”

Spent Grain: A Functional Ingredient for Food Applications

“…The extrusion process can improve the balance between soluble and insoluble dietary fiber contents, breaking polysaccharide bonds under mechanical stress, and releasing the content of phenolic compounds trapped in the dietary fibers through shearing. Among the undesirable aspects of extrusion is the Maillard reaction, which favors the production of acrylamide or the reduction in the content of essential amino acids; aspects that depend on the required processing conditions [ 100 ]. Gutiérrez-Barrutia et al studied the effect of extrusion on spent grain and found that extrusion had positive effects on spent grain, increasing the content of soluble dietary fibers, changes caused by the thermo mechanical process that can disrupt the cell wall matrix resulting in smaller and more soluble fragments.…”

“…Gutiérrez-Barrutia et al studied the effect of extrusion on spent grain and found that extrusion had positive effects on spent grain, increasing the content of soluble dietary fibers, changes caused by the thermo mechanical process that can disrupt the cell wall matrix resulting in smaller and more soluble fragments. Extruded spent grain can be considered a suitable ingredient for human consumption from a microbiological point of view [ 100 ].…”