Upcycling Brewer's Spent Grain and Barley Rootlets by Partial Substitution of Pea Protein Isolate in Extruded High...

This study evaluated how a partial substitution of pea protein isolate (PPI) with brewer's spent grain (BSG) or barley rootlets (BRs) affects high-moisture meat analogues (HMMAs). PPI was substituted with 10% and 20% with BSG or BRs, respectively. Extrudates were produced on a co-rotating twin-screw extruder at maximum temperatures of 140 °C and 160 °C. Extrudates were assessed for colour, moisture, firmness and fibre morphology. Furthermore, the technofunctional and nutritional properties of the raw materials were determined. Extrudates with BSG produced the darkest colour, whereas PPI and BR formulations exhibited the lightest. A stronger reddish tint was observed at 160 °C, while the colour within the yellow-blue spectrum was largely temperature-independent. Firmness was generally higher at 160 °C, consistent with lower end-product moisture. Side stream addition lowered protein content and weakened fibre formation, with the effect most pronounced for BRs. Overall, formulation was the dominant factor influencing lightness, while temperature modestly increased redness and firmness. Preliminary sensory evaluation supported these trends. Extrudates produced at 140 °C were perceived as having a more fibrous structure. Higher substitution levels resulted in a weaker, more crumbly texture. With respect to the environmental assessment, a 20% replacement of PPI with BRs or BSG reduced overall environmental impacts by up to 19% and climate impacts by up to 16%. With regard to the novel food status, the EU Novel Food Status Catalogue classifies BSG as not novel, whereas BRs are not novel only when used in food supplements. Any other food uses, other than as, or in, food supplements, might considered to be novel and consequently might need to be authorised under the novel food regulation framework prior to market placement.