In vitro protein digestibility and protein quality assessment of novel brewers' spent grain protein isolates

Mounting pressures on global food chains call for an urgent shift towards more sustainable food systems. Several ways to aid this transformation are the reduction of food waste through the valorisation of food processing side streams, and a shift from animal-based to plant-based proteins. As plant-based proteins are gaining popularity as alternatives to dairy and meat due to the rising demand for healthy, natural foods and their ethical appeal, it is essential that the protein quality of novel, alternative protein sources are evaluated. Brewers' spent grain (BSG) is a nutrient-rich brewing by-product which has been upcycled to produce everpro™ Dark Fraction (EDF) and a decolourised protein isolate known as everpro™ Light Fraction (ELF). This study investigates the in vitro protein and amino acid digestibility and in vitro digestible indispensable amino acid score (DIAAS) of EDF and ELF in comparison to pea, soy, and whey protein isolates using the static INFOGEST model. All ingredients demonstrated high digestibility (> 80%), while in vitro DIAAS of 51% and 37% were determined for EDF and ELF, respectively, lower values than the soy or whey proteins, but higher than or comparable to the two pea proteins studied. Differences were observed in the digestibility of individual amino acids in EDF and ELF and the resulting digestible indispensable amino acid ratio (DIAAR) values, indicating that the decolourisation process may be impacting protein quality. Overall, this study highlights how everpro™ ingredients can transform the food industry as alternative protein sources, enabling manufacturers to promote a more sustainable future.