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added anecdote about displacing trub and eliminating second boil for kettle sours
A variety of pyridine and pyrazine derived compounds are formed in malt (and other foods) during the malting process as a result of Maillard reactions and have been found to be major contributors to the "malty" flavor of beer. Examples of these compounds include 2-acetylpyridine, 3-acetylpyridine, methylpyrazine, forms of dimethylpyrazine, and trimethlpyrazine. These compounds have a range of flavor descriptors such as creamy, cardboard, grainy, and burnt sugar. For example, 2-acetylpyridine (2AP), also known as 1-pyridin-2-ylethanone, is described as having a malty-biscuity, corn-chip, corn tortilla, or popcorn flavor. These compounds (in particular 2AP) can easily be confused with forms of THP, but they are not the same as the varieties of THP explained above <ref>[https://en.wikipedia.org/wiki/2-Acetylpyridine 2-Acetylpyridine. Wikipedia. Retrieved 09/04/2018.]</ref><ref>[http://www.thegoodscentscompany.com/data/rw1012221.html 1-pyridin-2-ylethanone. The Good Scents Company website. Retrieved 09/04/2018.]</ref><ref>[https://www.aroxa.com/beer/beer-flavour-standard/2-acetyl-pyridine/ 2-acetyl pyridine. Aroxa website. Retrieved 09/04/2018.]</ref><ref>[https://onlinelibrary.wiley.com/doi/pdf/10.1002/jsfa.2740280218 Basic compounds contributing to beer flavour. Richard J. Harding, Harry E. Nursten, John J. Wren. 1977. DOI: https://doi.org/10.1002/jsfa.2740280218].</ref>. One indicator that a particular flavor might be THP instead of one of these malt-derived flavors is that THP is mostly detected on the aftertaste after swallowing, whereas these compounds are often detected during the swallow (although they can sometimes also be detected during the aftertaste).
An example of this possibly affecting beer has been reported in the kettle souring process at a commercial brewery, specifically when an extended second boil was performed. Alex Write Wright reported that At Halo Brewery brewmaster Callum Hay was able to remove a THP-like flavor from their kettle sours by displacing the trub at the bottom of the kettle and reducing eliminating the boil time during the pasteurization step of kettle souring (the second boil)and displacing the trub at the bottom of the kettle. It was hypothesized that the boiling and perhaps the trub at the bottom of the kettle that builds built up after a 24 hour souring process was being heated by their direct fire system, causing Maillard reactions that resulted in pyradines. By scrapping the trub off of the bottom of the boil kettle, and reducing replacing the second boil to with a 75°C (167°F) 10 minute rest/whirlpool, they were able to remove this flavor <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2381638895197644/?comment_id=2383092551718945&comment_tracking=%7B%22tn%22%3A%22R%22%7D Alex Wright. Milk The Funk Facebook thread on THP in kettle sours. 11/24/2018.]</ref>.
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