Upcycling of brewing by-products using lactic acid bacteria fermentation technology and analysis of their behaviour in a cereal-based applications
University College Cork
Barley rootlets (BR) and brewers spent grain (BSG) are by-products of the malting and brewing industries and are primarily used in animal feed and landfill. Due to the beneficial nutritional composition of BR and BSG (high fibre/protein) the current uses underestimate their maximum potential. BR are a relatively under explored material and review of the literature available on BR revealed extensive knowledge on the formation, processing, compositional quality, and potential applications of BR. In regard BSG, literature suggests high prospects for BSG in widely available cereal-based applications. However, further processing of BSG such as using lactic acid bacteria (LAB) fermentation technology are required to improve food product quality and further valorise BSG as a food ingredient. The incorporation of BSG and fermented BSG (FBSG) in a pasta matrix revealed inclusion of BSG and FBSG induced changes in gluten properties which depreciated pasta quality (reduced firmness and tensile strength) compared to semolina pasta. However, both BSG and FBSG pasta formulations performed more favourably than the wholemeal control from a techno-functional perspective. A greater reduction in the predicted glycaemic index with FBSG fortification compared to BSG suggested fermentation further enhances nutritional properties of BSG. A follow up study on the application of BSG and FBSG in a bread revealed similar defects to bread quality. Nonetheless, comparing BSG and FBSG breads, FBSG addition improved bread characteristics resulting in increased specific volume, reduced crumb hardness; restricted microbial growth rate over time; and slowed the release in reducing sugars over time during in vitro starch digestion. The success observed in the capability of LAB technology to functionalise BSG sparked interest in the application of LAB fermentation in BR processing. As a result, 5 fermented BR ingredients were developed and produced using Lactiplantibacillus plantarum FST 1.7 (BR-FST1.7), Lactobacillus amylovorus FST2.11 (BR-FST2.11), Weissella cibaria MG1 (BR-MG1), Leuconostoc citreum TR116 (BR-TR116) and Limosilactobacillus reuteri R29 (BR-R29). The changes in sugar/FODMAP/acid compositions; microbial metabolites and techno-functional properties of the developed BR ingredients identified each LAB fermentation imparted a unique set of characteristics to the BR ingredient, further affirming LAB fermentation technology as a functionalising processing technique. The developed BR ingredients were applied to a bread matrix to explore if characteristics of the LAB fermentation translated to the bread product. Inclusion of the fermented BR ingredients improved bread specific volume/reduced crumb hardness (BR-MG1, BR-TR116); substantially slowed microbial spoilage of breads (BR-R29); and produced breads with improved nutritional characteristics and varied sensory flavour profile (BR-FST2.11, BR-FST1.7). The outcome of this research thesis provides extensive knowledge on the effects of BSG and BR on pasta/bread quality as well as showcasing the potential of LAB fermentation technology as a valorisation technique for BR and BSG processing.
Brewing by-products , Malting by-products , Sustainability , Lactic acid bacteria fermentation , By-product valorisation , Fibre , Wheat bread , Brewers spent grains , Barley rootlets
Neylon, E. 2023. Upcycling of brewing by-products using lactic acid bacteria fermentation technology and analysis of their behaviour in a cereal-based applications. PhD Thesis, University College Cork.