| dc.description.abstract | This master's thesis explores the potential of Raffinose family oligosaccharides (RFO) from food side streams as an adjunct in sour beer production. The study investigates the effects of RFO on mixed fermentation with different bacterial strains and their enzymatic ability to hydrolyze oligosaccharides, the effect on yeast metabolism, and the overall flavor profile. A series of experiments were conducted using RFO enhanced wort as the base substrate, co-fermenting with various lactic acid producing bacterial strains, and yeasts. The fermentation process was monitored for sugar utilization, attenuation, organic acid production, pH, and volatile compound production. Tetrad analysis was performed to see if there was any discernable difference when adding RFOs. The study evaluated the different metabolic activities of a total of 10 bacterial strains and 4 yeasts. Their ability to metabolize RFO was assessed by monitoring their growth curves, as well as by a variety of chemical analysis techniques, at time intervals of 7, 14, and 19 days with the aim of producing sour beer within the normal time frame of traditional non-sour beer. The results suggest that the use of RFO as substrate in the production of beer is contributing beneficially towards the overall flavor and fermentation profile. It led to an increase in ethanol concentration in beer fermented with Saccharomyces cerevisiae, demonstrating that at least a proportion of the RFO extract can be fermented by brewer’s yeast. However, the impact of RFOs on mixed fermentation, including the utilization of the oligosaccharide constituents, showed mixed results. Multiple strains demonstrated the ability to ferment individual constituents of RFO, but in co-fermentations, the fermentation conditions appeared to primarily promote organic acid production, rapidly lowering the wort's pH, inducing stress to the yeast, and affecting the production of metabolites, especially aldehydes and esters. The sensory evaluation of the experimental beer fermented with RFOs displayed a discernible differentiation from the beer fermented without RFOs, without increasing unwanted off-flavor associated compounds. This demonstrates that incorporating RFOs as an adjunct in the production of sour beers has promising potential. In conclusion, the incorporation of RFOs as a substrate in sour beer fermentation holds promise, with a discernable difference in organic compounds produced, but a more comprehensive understanding of the process and optimization of fermentation conditions are crucial to achieving consistent and desirable outcomes, as well as to quantify the enzymatic ability to hydrolyze the constituents of RFO. | |
