Yeasts from the Styrian orchard meadow and their potential for the production of alcohol-free beer

Abstract

Alcohol-free beer has become an asset even for small-scale breweries, since the consumption of low and non-alcoholic beverages is increasing steadily. Hence, the search for new, cost-effective and efficient methods of producing non-alcoholic beers that can also be realised by small breweries has also intensified. Maltose-negative yeast species play a key role in some of these low-threshold strategies to establish new and innovative alcohol-free beer products on the market. Due to this, the quest for new maltose-negative yeast species and strains becomes increasingly important. The ideal yeast species for this application shows an aroma profile with high consumers’ acceptance and a low degree of attenuation, preferably accompanied by a fast fermentation rate. Since the large part of already known yeast species which are associated with trees, flowers and fruits are maltose-negative, fruit plantations seem the appropriate hunting grounds for viable candidates. Meadow orchards, which are extensively cultivated and traditionally tilled, promise a rich bounty of yeast species diversity. In addition, local breweries may also be able to utilise yeasts from their own region as a valuable fermentation and marketing asset to refine and to promote their own products. The meadow orchard investigated in this study harbors at least ten different microfungal species, of which three were tested in fermentation trials: Torulaspora delbrueckii, Candida peoriensis and Filobasidium wiringae. The species were inoculated and enriched in culture media, suspended in a standardized mixture (Pilsner Malt (10 % extract w/w), 20 IBU/L) and incubated for seven days at 25 °C and 60 % relative humidity. Continuously during the fermentation, the extract and pH-value were documented. Additionally, afterwards the sugar utilisation of T. delbrueckii and C. peoriensis was analysed. The isolated strain of Torulaspora shows promising properties for producing alcohol-free beer, whereas C. peoriensis may be utilised in co-fermentations or in the production of fermented beverages other than beer.