Changes

One study compared the levels of isovaleric acid in a kettle soured beer (flushed with CO2), a sour mashed beer (flushed with CO2), and a beer co-fermented with ''Lactobacillus amylovorus'' and US-05. They found that there was a significant increase in isovaleric acid when the ''Lactobacillus'' and US-05 were co-fermented (1.15 mg/L vs 0.50-0.83 mg/Lsee the table below). The authors suggested that this might be due to the release of the amino acid precursors by the ''Lactobacillus'' towards the end of its life cycle when it was allowed to survive in a co-fermentation, versus being killed in the kettle souring/mash souring batches <ref name="peyer_2017">[http://www.asbcnet.org/publications/journal/vol/2017/Pages/ASBCJ-2017-3861-01.aspx Sour Brewing: Impact of Lactobacillus amylovorus FST2.11 on Technological and Quality Attributes of Acid Beers. Lorenzo C. Peyer, Martin Zarnkow, Fritz Jacob, David P. Schutter, Elke K. Arendt. 2017.]</ref>. {| class="wikitable sortable"|-! Method !! Amount of IVA <ref name="peyer_2017" />|-| US-05 Only (control) || 0.83|-| Mash Souring with ''L. amylovorus'' and primary fermentation with US-05 || 0.72|-| Kettle Souring ''L. amylovorus'' and primary fermentation with US-05 || 0.50|-| Co-fermentation with ''L. amylovorus'' and US-05 || 1.15|-|}