Hydro-mechanical processing of brewer's spent grain as a novel route for separation of protein products with differentiated techno-functional properties

Abstract

Hydro-mechanical processing using a colloid mill with a large gap setting leads to the preferential breakup of the residual aleurone and endosperm tissues of brewer's spent grain, forming a protein rich fines material with small particle size around 1–10 μm. This fraction can be separated from the coarser husk fraction by centrifugation, giving a protein product with enhanced techno-functional properties. The fines have good stability in aqueous suspensions, with potential for stabilising other particulate materials in food or drink formulations. The fines particles can stabilise oil-water emulsions, possibly through a Pickering mechanism, which may also support use in food applications. Fines suspensions have strong shear-thinning behaviour, which may be beneficial from a textural or transport perspective. Spray drying of fines suspensions is shown to avoid particle coalescence, which is important for effective resuspension on rehydration. The high surface area of the fines also leads to more efficient digestion by proteases. A novel hydro-mechanical milling process has been investigated for separation of a protein fine fraction from brewer's spent grain having enhanced techno-functional properties. The small particle size of the fines would be a key attribute for formulation in shake or smoothie products, where sensory attributes of the product would not be compromised and the properties of the fines could confer stability against settling. Applications may be found for the fines material as an ingredient in spreads and sauces or infant purees, in-particular where it might be used to stabilise of products based on oil-water emulsions. The market for protein-rich ingredients for foods and drinks is already established in the fitness and well-being market, as derived from other vegetable or cereal sources such as hemp, pea or rice. This controlled pre-milling step is also shown to lead to greater rate and extent of protease digestion of spent grain, which may be of value for generation of protein and peptide products for well-being and cosmetics applications. • Hydro-mechanical processing is used to create a unique protein rich fines material with small particle size around 1-10 μm. • The protein rich fine fraction can be physically separated from the coarser husk fraction by centrifugation. • Aqueous suspensions of protein rich fines might be used to stabilise other particulate materials in food or drink formulations. • The protein rich fines may stabilise oil-water emulsions by a Pickering type mechanism, also leading to food applications. • Protein rich fines suspension have strong shear-thinning behaviour, beneficial for texture and for flow and transport.