Evaluation of spontaneous fermentation with backslopping method for the production of alcoholic ginger beer

Ginger beer is a fermented beverage made from the rhizomes of Zingiber officinale and originated in England in the mid 17th century as a low alcohol beer. This drink can be produced using a microbial consortium called the Ginger Beer Plant (GBP) or follows the backslopping method, consisting of a small amount of fermented material as inoculum in a new batch. In addition, an alcoholic version can be obtained with commercial yeasts in a controlled fermentation. In this last preparation, the grain wort or suga r substrate (mainly sucrose) could be diluted for low alcohol beer production. However, the most common commercial ginger beer is made with carbonated water and ginger syrup/extract. Few studies have focused on the production of ginger beer, and there are no investigations on the use of non Saccharomyces yeasts in controlled fermentation. The aim of this study was the analysis of the fungal community involved in ginger bug activation a nd beer fermentation using the backslopping method. Two different ginger rhizomes, labelled A and B, were used for the fermentation trials. During the process, native yeasts were isolated at different times (24, 36, 48, 72 and 96 hours during the activation and 0, 7 and 14 days during the fermentation). Furthermore, the sugar consumption measured the weight loss and the pH of ginger bug and gi nger beer were analyzed. A strain of Candida sp. and Wickerhamomyces sp. dominated in the ginger A and B batch samples, respectively, during activation and fermentation. No significant sugar consumption was observed in both. This occurrence could be explai ned by the inability of these native strains to ferment sucrose. Subsequently, these two batches were inoculated with a commercial strain of Saccharomyces cerevisiae and Torulaspora delbreuckii to complete the fermentation. In conclusion, this preliminary study evidenced that native yeasts occurring in the spontaneous fermentation obtained by the backslopping method can not ensure the production of alcoholic ginger beer. In this case, the use of starter yeasts seems necessary . Hence, the evaluation of the effects of S. cerevisiae and non Saccharomyces yeasts, such as T. delbrueckii, on chemical and sensory traits deserves further investigations.