On the suitability of alternative cereals, pseudocereals and pulses in the production of alcohol-reduced beers by non-conventional yeasts

The growing interest in non-alcoholic and low alcohol beers (NABLAB) has fuelled research into innovative production methods. One means to produce NABLAB is through limited fermentation by non-Saccharomyces yeasts which have a naturally low fermentative capacity in cereal-based wort substrates. At the same time, adjunct brewing, the partial replacement of barley malt on the grain bill, enjoys growing popularity. In this study, 13 cereals, pseudocereals, and pulses were investigated for their suitability to produce a wort with limited amounts of fermentable sugars. Subsequently, the fermentation performance of two non-Saccharomyces yeast strains, namely Cyberlindnera subsufficiens C6.1 and Lachancea fermentati KBI 12.1, in the produced worts was investigated and compared to that of a brewers’ yeast strain. The worts were produced by harnessing endogenous amylolytic enzyme activity or the addition of an external amylase and analysed for their sugar composition and free amino acids (FAA) profile. All alternative substrates without endogenous β-amylase activity were found to be suitable for producing worts with a high proportion of unfermentable sugars. However, the extract yield was low for the pulses and most worts exhibited a low and/or unbalanced FAA profile. The ethanol production was limited and mostly dependent on the sugar spectrum of the worts and the sugar utilization characteristics of the applied yeast strains. The (partial) substitution of barley with alternative substrates when producing NABLAB by non-Saccharomyces yeast can be a means to alter the sugar and FAA profile of the wort, but must be considered in concert with the yeast strains’ characteristics.