13,700
edits
Changes
Grain
,grammar
* 2016 Weyermann Barke
The grain samples before inoculation hosted a large variety of microbes, but immediately after inoculating the malted grains into 110°F wort, all of the grain samples were dominated by ''Weissela cibaria'' (ranging from 92-99% across all samples), a Gram-positive lactic acid bacteria that is in the same order but a different family as ''Lactobacillus''<ref>[https://www.microbiologyresearch.org/docserver/fulltext/micro/161/4/914_mic000053.pdf Genomics of Weissella cibaria with an examination of its metabolic traits. Kieran M. Lynch, Alan Lucid, Elke K. Arendt, Roy D. Sleator, Brigid Lucey and Aidan Coffey. 2015. DOI: 10.1099/mic.0.000053.]</ref>. All but one of the grain samples also had a much smaller but not insignificant population of ''Salmonella bongori'' (1-4% across all samples), which has been associated with non-lethal food poisoning <ref>[https://en.wikipedia.org/wiki/Salmonella_bongori#Pathogenicity_and_epidemiology "Salmonella_bongori". Wikipedia. Retrieved 06/15/2017.]</ref>. There were also trace populations of other bacteria such as ''Enterobacter'' spp., ''Pantoea'' spp., ''Erwinia'' spp., and ''Lactococcus lactis'' in most of the samples. There was a significant ''L. lactics'' population in the 2016 Weyermann Barke, as well as ''Enterobacter aerogenes'' <ref name="blueowl_2017">[https://experiment.com/projects/mapping-the-sour-beer-microbiome/results "Mapping the sour beer microbiome". Matthew Bochman and Jeff Young. Experiment.com. 2017. Retrieved 06/15/2017.]</ref>.
After 24 hours of continued 110°F inoculation incubation in the wort, all but 2 samples were almost completely dominated by ''Weisella cibaria'' (98-99% across all samples). The 2016 Weyermann Barke also had a small 5% population of ''Lactococcus lactis'' (5%). The 2016 Breiss Merit 57 was significantly different than the other grain samples, and was the only sample with a very large population of several species of ''Lactobacillus'' (38% ''Lactobacillus reuteri'', 23% ''Weissla cibaria'', 15% ''Lactobacillus delbruekii'', 12% ''Pedioccocus pentosaceus'', 8% ''Lactobacillus fermentum'', and 3% ''Lactobacillus helveticus''). This data indicates that ''Lactobacillus'' is generally not the dominant organism when inoculating with grain samples at this temperature, despite popular belief. It was the thought of the authors that ''Lactobacillus'' species might dominate at lower or higher temperatures, but more studies are needed to show this. In addition, only a very small population is required to begin with on samples that do, and once inoculated into wort at 110°F, their population will increase significantly <ref name="blueowl_2017" />.
After 48 hours, ''Weissella cibaria'' continued to dominate all of the grain samples except the 2016 Breiss Merit 57 (note that the 2015 harvest of Breiss Merit 57 was dominated by ''Weisella cibaria'', indicating that the barley variety is not the determining factor of which microbes might be dominant, but that the harvest year is more important). Two samples, the 2015 Breiss Merit 57 and the 2016 Blacklands Endeavor, also saw an increase in the population of ''Shiggela sonnei'' (2.5%). The ''Salmonella bongori'' was still present in samples after 48 hours, but decreased to less than 1% <ref name="blueowl_2017" />.
Some of the organic acids and alcohols were also measured in this experiment. Most of the samples created fairly high and similar levels of lactic acid, followed by a smaller amount of acetic acid, and then followed by trace amounts of citric, pyruvic, malic, and succinic acids. The 2016 Breiss Synergy had much more lactic acid, acetic acid, and noticably noticeably more succinic acid the all the other samples. It also had considerably more ethanol produced, indicating that a heat tolerant wild yeast may have fermented this sample <ref name="blueowl_2017" />. [[Butyric Acid]] and [[Isovaleric Acid]] were not measured due to the difficulty in measuring these acids at the lab that was used <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1660708117290729/?comment_id=1661783767183164&reply_comment_id=1664682886893252&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Edwards, John. Milk The Funk facebook group. 04/24/2017.]</ref>.
The experiment concluded that using grain to inoculate wort could potentially be done so in a controlled manner, producing predictable and consistent results. It was stated that more studies need to be conducted to explore the variability in brewing process such as temperature and incubation times. For example, while the ''Weisella cibaria'' dominated at 110°F, it is reported that it doesn't tolerate temperatures above 113°F, and ''Lactobacillus'' might dominate at temperatures around 90-95°F or maybe at temperatures above 113°F <ref name="blueowl_2017" /><ref>Private correspondence with Jeff Young by Dan Pixley. 06/29/2017.</ref>.
Various concerns on possible cross contamination associated with the methodology of the referenced experiment have been discussed with the authors on [https://www.facebook.com/groups/MilkTheFunk/permalink/1660708117290729/ this MTF thread].