Control of residual maltose in low-alcohol beer produced by non-Saccharomyces yeast with enzymatic treatment.

Non-alcoholic and low-alcohol beer (NABLAB) production by maltose-negative non-Saccharomyces yeast (NSY) runs the risk of excessive sweetness due to the high residual maltose in the finished beer which may overshadow the unique flavors produced by the NSY. The goal of this study was to modify the fermentable sugar profile in wort to better suit maltose-negative NSY, resulting in low residual maltose worts while maintaining low ethanol levels. This was achieved by adding amyloglucosidase (AMG) to increase the proportion of glucose by partially hydrolyzing maltose and maltotriose. Two treatments were selected from AMG-treated time-course mash experiment to produce either moderately elevated or highly elevated glucose levels with either barley malt or barley malt extract. Fermentation was then performed using nine different NSY and compared to Saccharomyces cerevisiae. Most NSY produced significantly less ethanol than S. cerevisiae under these conditions, while leaving behind relatively low levels of maltose (<10 g/L). Lower ethanol production was found to be partially driven by diversion of sugar-derived carbon to non-ethanol pathways, including organic acids and glycerol. Overall, the use of high-glucose worts appears to be a promising approach to produce NABLAB by NSY with the potential for improved sensory properties.