Changes

After the 7 days of the primary fermentation, the beer was transferred to a secondary fermenterand remained there for four to five weeks. Both the yeast and bacteria populations saw a decline during the transfer, and then a small and gradual growth in secondary with the final yeast count being 4.3x10⁵ in the "heavy beer" and 6.4x10³ in the "light beer". Lactic acid bacteria grew much faster and became dominate in the "light beer", whereas in the "heavy beer" they grew more slowly and yeast remained the dominate microbe. This is explained by there being more sugars in the "heavy beer", which gave the yeast the advantage. Acetic acid bacteria were still not detected during secondary fermentation <ref name="Martens"></ref>. Lactic acid begins to be produced as well during secondary fermentation, with about a third of it being L-lactic acid and two thirds of it being D-lactic acid <ref name="Verachtert">[BELGIAN ACIDIC BEERS Daily Reminiscences of the Past. Hubert Verachtert, Guy Derdelinckx. 2014.]</ref>.

During secondary fermentation, ''L. delbruekii ssp delbruekii'' strains dominated over the other lactic acid bacteria found. Additional strains of ''L. plantarum'' and ''L. coryneformis'', and an additional strain of ''L. brevis'' was found in the "heavy beer". Other than the dominating ''L. delbruekii ssp delbruekii'' strains, only a few strains of ''L. brevis'' were found in the "light beer" <ref name="Martens"></ref>. The "light beer" appeared to have a a smaller diversity of microbes.