Changes

THP or THP-like flavors have been reported in the kettle souring process in commercial brewing. This could be caused by using a heterofermentative species of ''Lactobacillus'' that is able to produce THP, but it has also been reported when an extended second boil was performed. Alex Wright reported that At Halo Brewery brewmaster Callum Hay was able to remove a THP-like flavor from their kettle sours by 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 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 replacing the second boil 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 group thread on THP in kettle sours. 11/24/2018.]</ref>. However, Alan Simons (and possibly others) contradict this by reporting no THP-like flavors when doing an extended second boil after kettle souring <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2381638895197644/?comment_id=2383092551718945&reply_comment_id=2383152158379651&comment_tracking=%7B%22tn%22%3A%22R6%22%7D Alan Simons. Milk The Funk Facebook group thread on THP in kettle sours. 11/24/2018.]</ref>. Josh Kauffman reported that by switching from a 60 minute post-boil (after souring the wort with ''Lactobacillus'') to a 15-20 minute pasteurization rest at 180°F reduced the THP-like flavors in their kettle soured beer <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2425689770792556/ Josh Kauffman. Milk The Funk Facebook group thread about THP in kettle sours. 12/18/2018.]</ref>. [https://www.facebook.com/groups/MilkTheFunk/permalink/2436338106394389/ Several other brewers in MTF] have also reported reducing THP-like flavors by shortening the second boil. There ae are no controlled experiments that we know of that confirm any of these reports.