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====Phenol Production====
Phenols such as 4-vinylphenol (4VP, barnyard, medicinal) and 4-vinylguaiacol (4-VG, clove) can be produced in beer by the decarboxylation of hydroxycinnamic acids (HCAs), which are found in malt. While both ''Saccharomyces'' (only by "phenolic off flavor positive/POF+" strains) and ''Brettanomyces'' strains have varying capabilities based on strain of converting hydroxycinnamic acids to their vinyl derivatives <ref name="Lentz">[http://www.mdpi.com/2304-8158/4/4/581/htm Analysis of Growth Inhibition and Metabolism of Hydroxycinnamic Acids by Brewing and Spoilage Strains of Brettanomyces Yeast. Michael Lentz and Chad Harris. 2015.]</ref>, ''Brettanomyces'' is also able to reduce these vinyl phenol derivatives to ethyl phenol derivatives. Phenolic acid decarboxylase (PAD) is the enzyme that converts the HCAs into vinyl phenols. Vinyl reductase (VA) is the enzyme that reduces vinyl phenols to ethyl phenols <ref>[https://www.facebook.com/groups/MilkTheFunk/1632316743463200/ Analysis of phenolic acid decarboxylase enzyme from the wine spoilage yeast Brettanomyces bruxellensis (poster). Mike Lentz, Jamie Lynch, Pricilla WlatersWalters, Rachel Licea, Henok Daniel, Kimberly Pereira. 2017.]</ref>.
These vinyl derivatives have similar tastes to the ethyl derivatives but have lower flavor thresholds. Levels of all compounds produced vary depending on species and strain of ''Brettanomyces''. Some data supports that pitching rate does not have an effect on how much phenol content is produced by ''Brettanomyces''<ref name="MTF_Brett_Secondary">[http://www.milkthefunk.com/wiki/Brettanomyces_secondary_fermentation_experiment Brettanomyces secondary fermentation experiment. Milk The Funk Wiki. Lance Shaner and Richard Preiss. Retrieved 04/21/2016.]</ref>. This contradicts the somewhat popular belief that under-pitching ''Brettanomyces'' produces more "funky" flavors.