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A more recent study by Snaewaert et al. (see reference <ref name="snauwaert"></ref>) looked at the microbial and metabolic composition in the finished beer of the same brewery as Martens et al., as well as two other Flanders Red Ale breweries using "state of the art" DNA sequencing methods. Three samples were analyzed (A, B, and C) from each brewery (1, 2, and 3). As expected, there were both similarities and differences between the three breweries tested, as well as some differences between the individual beers from each brewery. The bacterial populations for Breweries 1 and 3 were similar across all samples, whereas Brewery 2's samples had a larger difference in the three samples of its beers. The yeast populations were similar between all samples for Brewery 1, whereas Breweries 2 and 3 had a larger difference in yeast populations between their three samples of beer <ref name="snauwaert"></ref>. In summary, Brewery 1 (presumed to be Rodenbach) had similar populations of bacteria and yeast across all samples of their beer, whereas Brewery 3 only had similar populations of bacteria and not yeast across all samples of their beer, and Brewery 2 had the least amount of similarity in yeast and bacteria populations between their beer samples.
Overall, the samples were mostly dominated by ''Pediococcus damnosus'' and ''Brettanomyces bruxellensis'', except for two samples of Brewery 2 that were dominated by ''Acetobacter'' (smaller amounts of ''Acetobacter'' in Brewery 1 were identified as ''Acetobacter pasteurianus'', and might be the same species in Brewery 2), and one sample from Brewery 2 and two samples from Brewery 3 that were dominated by an unidentified yeast. Note that these findings conflicted with the findings of Martens et al. who identified ''P. parvulus'' as the dominating ''Pediococcus'' species. These two species are closely related, and an explanation of this discrepancy between the two findings was never found. ''Acetobacter'' numbers were higher in Brewery 1 and 2, and lower in Brewery 3, and were associated with the high acetic acid amounts found in the beers. Small numbers of ''Lactobacillus'' were found in all samples. ''Weissella'' and ''Leuconostoc'' were found in some samples from Brewery 2, whereas only trace amounts of ''Wessella'' were found in one samples from Brewery 3. A significant amount of ''Pichia'' yeast were found in two Brewery 2 samples, and trace amounts in other samples, as well as trace amounts of ''Candida'' and ''Kregervanrija'' yeasts . Although detected with DNA sequencing methods, ''Lactobacillus'', ''Candida'', other yeast could not be isolated and grown under lab conditions <ref name="snauwaert"></ref>.
====Metabolic Composition====
Snaewaert et al. also looked at the metabolic composition of finished beers in the three breweries. Glucose was completely gone from the samples, but substantial concentrations of maltose, matotriosemaltotriose, tetraosemaltotetraose, pentaosemaltopentaose, and hexaose maltohexaose were still present. This contrasts with the relatively high glucose and fructose found in finished bottled versions of these beers, which indicates that the beers are back-sweetened with young beer or with residual sugar or even possibly just some form of sugar at bottling time <ref name="snauwaert"></ref>.
Overall the flavor of these beers was dominated by ethanol, lactic acid, acetic acid, ethyl acetate. Across the samples there was a presence of isoamyl alcohol (31-150mg/L) and isoamyl acetate (1.99-6 mg/L), and an absence of 2-phenyl ethanol and 2-phenylethyl acetate in both the matured beers and the bottles versions of those beers. Small amounts of propionic acid, isobutyric acid, ethyl hexanoate, and ethyl octanoate were found. Higher levels of ethyl acetate were found compared to the Martens et al. study, and no ethyl decanoate, which is a typical ester found in gueuezegueuze, was found. Just as the microbial populations of Brewery 2 differed from Breweries 1 and 3, so did it's overall metabolite content. Higher levels of acetic acid were found in Brewery 2, which was attributed to high levels of ''Acetobacter'' populations. Additionally, all three of the samples from Brewery 2 differed from each other as metabolic content, which was also attributed to the microbial population differences between each of Brewery 2's samples <ref name="snauwaert"></ref>.
==See Also==