Functional and Nutritional Properties of Proteins From Barley Malting By-Products

Nowadays, global demand for alternative protein sources is rising, and exploitation of by-products can concurrently meet the challenges of integrating sustainability and circular economy in the food industry. Barley malt rootlets represent the main by-product of the malting industry and are normally discarded as animal feed. In this work, the protein concentrates obtained after alkali extraction of industrial by-products were characterized (amino acid composition, SDS page and protein digestibility) with particular regard to the techno-functional properties (solubility, foaming and emulsifying abilities, water holding capacity (WHC), and fat absorption capacity). Data were further compared with those obtained on common plant-derived proteins such as soy, pea, and rice, to elucidate the potential application of proteins from malt rootlets in novel food formulations. Nutritionally, significant levels of lysine were detected (-7.0 g/100 g proteins) with comparable digestibility data to other legume protein sources (-75%). The solubility trend aligned with soy and pea proteins, being close to 90% in the pH range 11-12. Foaming and emulsifying abilities were weaker than soy and pea proteins, while WHC (-6 mL/g) exceeded that of other proteins thus evidencing its potential in liquid or semi-liquid formulations. Overall, both malt rootlets and malt rootlets pellet, the true industrial by-product, can potentially be up-cycled materials for protein rich ingredients with suitable nutritional and technological performance. PRACTICAL APPLICATIONS: The study provides an insight into the functional properties of proteins in barley malt rootlets. Results support the up-cycle of brewing by-products for the recovery of high-proteins ingredients.