Pea-Derived Raffinose-Family Oligosaccharides as a Novel Ingredient to Accelerate Sour Beer Production

This study investigated raffinose family oligosaccharides (RFOs) derived from pulses as selective carbon sources for sour beer production. Fourteen lactic acid bacteria (LAB) were screened for growth in media supplemented with RFOs. Furthermore, the influence of ethanol and isomerized α-acids on the bacterial growth was investigated. While most LAB grew in the presence of RFOs, few did so in the presence of ethanol and α-acids. Some of the LAB with tolerance to these stressors were then combined with <i>Brettanomyces claussenii</i> to create classic-style sour beers with or without RFOs. These were characterized chemically, physically, and sensorially. Sour beers made with RFOs were evaluated as being comparable to a commercial Belgian sour beer for some sensory characteristics. Furthermore, the sensory analysis revealed significantly increased acidity levels and differences in flavor and taste between beers fermented with and without RFOs, which was underpinned by chemical analysis. Crucially, beany off-flavors, which are a common problem with pulse-derived ingredients, did not increase upon RFO addition. Thus, by combining selected LAB with RFOs, we successfully utilized a food sidestream and expanded the possibilities for brewing sour beers in a controlled manner in a short time. This is in contrast to the lengthy process used for traditional sour beers.