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

Abstract

<p>This study aimed to produce and investigate Ale-type barley-spelt beers with low-alcohol levels by utilizing two different non-<em>Saccharomyces</em> yeasts, <em>Torulaspora delbrueckii</em> and <em>Saccharomycodes ludwigii</em>, and compare them to Ale-beers fermented with commercial Ale-yeast (<em>Saccharomyces cerevisiae</em>). 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 <em>S</em>. <em>cerevisiae</em> resulted in extensive sugar consumption, leaving only small amounts of maltose, maltotriose and fructose. By contrast, <em>T</em>. <em>delbrueckii</em> and <em>S</em>. <em>ludwigii</em> retained most of the maltose and maltotriose, but no fructose was detected. <em>S</em>. <em>cerevisiae</em> produced the highest ethanol concentrations (3.39 % v/v), whereas <em>T</em>. <em>delbrueckii</em> and <em>S</em>. <em>ludwigii</em> yielded significantly lower levels (1.24 % v/v and <1.0 % v/v, respectively). <em>S</em>. <em>cerevisiae</em> 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-<em>Saccharomyces</em> fermentations. Furthermore, non-<em>Saccharomyces</em> fermentations generated higher sulfur compound levels that could impact beer aging. In conclusion, <em>S</em>. <em>cerevisiae</em> demonstrated high efficiency in sugar assimilation and ethanol formation, while <em>T</em>. <em>delbrueckii</em> and <em>S</em>. <em>ludwigii</em> showed limited fermentation performance, indicating their potential in producing low-alcohol beers with potentially distinct and milder sensory properties.<br></p>