Utilization of Saccharomycodes ludwigii and Torulaspora delbrueckii in production of Ale-type beers with low alcoholic contents

This study aimed to produce and investigate Ale-type barley-spelt beers with low-alcohol levels by utilizing two different non-Saccharomyces yeasts, Torulaspora delbrueckii and Saccharomycodes ludwigii, and compare them to Ale-beers fermented with commercial Ale-yeast (Saccharomyces cerevisiae). The effects of both primary and bottle fermentation on sugar utilization, ethanol yield, and volatile compound profiles were examined. Volatile compound profile and contents were determined after primary and bottle fermentations with GC-MS. Wort contained high initial levels of maltose (62.5 g/L), maltotriose (42.3 g/L), fructose (22.0 g/L), and sucrose (17.9 g/L). Fermentation with S. cerevisiae resulted in extensive sugar consumption, leaving only small amounts of maltose, maltotriose and fructose. By contrast, T. delbrueckii and S. ludwigii retained most of the maltose and maltotriose, but no fructose was detected. S. cerevisiae produced the highest ethanol concentrations (3.39 % v/v), whereas T. delbrueckii and S. ludwigii yielded significantly lower levels (1.24 % v/v and <1.0 % v/v, respectively). S. cerevisiae increased the contents of many volatile compounds after both fermentation types, while only a few volatile compounds were detected in significant quantities in the non-Saccharomyces fermentations. Furthermore, non-Saccharomyces fermentations generated higher sulfur compound levels that could impact beer aging. In conclusion, S. cerevisiae demonstrated high efficiency in sugar assimilation and ethanol formation, while T. delbrueckii and S. ludwigii showed limited fermentation performance, indicating their potential in producing low-alcohol beers with potentially distinct and milder sensory properties.