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The industrial lambic beer fermentation process

Nowadays, lambic beers are also produced on an industrial scale in several breweries in Belgium and the brewing processes have even been adopted in the USA, where the resulting beers are called American coolship ales (ACAs; see below). The technical characteristics of both traditional and industrial production processes differ, which might influence the microbiota and thus the fermentation process. In an industrial process, lambic wort is made using an infusion mashing rather than a turbid mashing scheme, the wort is acidified at the end of the wort boiling to pH 4.0 using lactic acid and, finally, the wort is pre-chilled after boiling, before being transferred to the cooling tun. Together, this enables an industrial brewery to produce lambic beers throughout the year. The data presented below were taken from Spitaels et al. (2015b).

In contrast to a traditional lambic beer fermentation process, none of the cooling tun samples of an industrial brewing process yielded DNA or isolates. Furthermore, members of the Enterobacte- riaceae could not be isolated, nor could their DNA be detected through PCR-DGGE experiments. Most likely, the acidification of the boiled wort before chilling prevented the growth of Enterobac- teriaceae, which is known to be inhibited below pH 4.0 (Priest and Stewart, 2006). Bacteria and yeasts were isolated as soon as the cooled wort was transferred into the casks. These early isolates were identified as Pichia kudriavzevii, D. hansenii and Ace- tobacter orientalis and AAB were isolated from the start of fermentation up to 6 months, which again contrasted with a traditional fermentation process. S. cerevisiae was already dominant after 1 week of fermentation, but also B. bruxellensis was isolated from that sample. Pediococcus damnosus was present from 3 weeks onwards. If the dominance of B. brux- ellensis and P. damnosus is again used to demarcate the maturation phase, such as in a traditional lambic beer fermentation process (Spitaels et al., 2014c; Van Oevelen et al., 1977; Verachtert and Iserentant, 1995), then the main fermentation phase lasted for one month only. Hanseniaspora uvarum was not characteristic, as it was only found in the initial samples of a sluggishly starting fermentation batch, which confirmed that this species has a low fermentative capacity, as discussed above.

Overall, the microbiota present during the maturation phase was the same as the one in a traditional lambic beer fermentation process, although the species diversity was simpler. Similar to a traditional lambic beer fermentation process, the main fermentation phase of an industrial lambic beer fermentation process was dominated by Saccharomyces spp. The dominant isolation of S. cerevisiae from one batch in the warm summer months supported the hypothesis that the dominance of S. pastorianus at the end of the lambic beer fermentation process in a traditional brewery was due to the tolerance of the maltose and maltotriose transporter of this species towards low temperatures.

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