Characterisation and functionalisation of protein from brewer's spent grain and its application in novel beverages
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Date
2026-05-07
Authors
Ahern, Niamh
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University College Cork
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Abstract
Barley and rice protein isolate (BRPI), upcycled from brewers spent grain (BSG), is a major byproduct of the brewing industry. This thesis investigated the characterisation and functionalisation of BRPI with a focus on its application in novel beverages, specifically acidic, water-based beverages where incorporation of plant-based proteins (PBP) faces solubility, stability and sensory challenges. In particular, this research explores BRPIs composition, techno-functional properties, sensory characteristics and its utilisation in acidic water-based, soft drinks. Initial stages involved a comprehensive retail market survey and physicochemical analysis of animal and plant derived protein soft drinks, identifying gaps in formulation and assessing the scarcity of PBP soft drink options. Among the 138 protein soft drinks surveyed, animal-based proteins (ABP) dominated the market, primarily whey protein isolate (WPI) and collagen hydrolysate (CH). Only 18% of the products contained PBP options, predominantly formulated with pea protein isolate/hydrolysate (PPI/H) or single amino acids. The digestibility characteristics of BRPI, determined using the dynamic tiny-TIM in vitro model, achieved a nitrogen bio-accessibility >90% and a DIAAS of 67% (lysine-limited) that outperformed conventional PBP isolates including pea, soy and rice while closely matching WPI’s techno-functional properties. Decolourised BRPI, lighter in colour than original BRPI, were both characterised and compared to assess differences in functionality and sensory quality. Both exhibited high solubility (>80%) across various pH ranges, including acidic conditions. Decolourised BRPI displayed higher lubricating properties and reduced flavour profiles due to reduced Maillard reaction associated aroma compounds. Application trials were conducted across a range of commercially available soft drink and non-alcoholic beverage systems to evaluate the impact of BRPI, at various concentrations, on their functional properties. The protein concentration added affected the pH, stability and viscosity of the formulations. Fermentation of BRPI with three different lactic acid bacteria (LAB) (Lactiplantibacillus plantarum FST 1.7, Leuconostoc citreum TR116 and Lactobacillus amylovorus FST 2.11) demonstrated its suitability as a substrate for producing high protein fermented beverages. The strains showed specific differences in their techno-functionality and sensory attributes including fruity and dairy like flavours. While all strains showed acidification only TR116 produced mannitol. This research provides approaches for valorising brewing side streams for novel high protein beverages that can help support consumers struggling to meet adequate protein requirements.
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Keywords
Soft drinks , Brewers spent grain protein , Sustainability , Beverages , Plant proteins , Digestability , Techno-functionality , Fermentation
Citation
Ahern, N. A. 2026. Characterisation and functionalisation of protein from brewer's spent grain and its application in novel beverages. PhD Thesis, University College Cork.