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added link to Gareth Young's post on MTF under Foam Degredation
Proteolytic activity has been shown to decrease as pH falls below 5.0 for some species of ''Lactobacillus'' <ref name="Haq_Mukhtar"></ref>. In order to combat poor head retention in beers that are soured with ''Lacto'', it has been suggested by German brewing scientist, Burghard Hagen Meyer, to [[Sour_Worting#How_to_Pre-Acidify|lower the pH of the wort to 4.5-4.8]] with food grade lactic acid or phosphoric acid before pitching ''Lactobacillus'' <ref name="Gail">[https://sourbrewster.wordpress.com/2012/09/18/berliner-weisse-the-old-time-kettle-souring-technique/ ''Berliner Weisse – the old-time kettle-souring technique.'' Brewing Sour blog, by Gail Ann Williams.September 18, 2012. Retrieved 7/7/2015.]</ref><ref>[http://ingenuitybrew.blogspot.com/2013/06/berliner-weisse-test.html ''Berliner Weisse Test''. Ingenuity Brew Blog. June 4, 2013. Retrieved 7/7/2015.</ref><ref>[http://www.themadfermentationist.com/2012/06/100-lactobacillus-berliner-weisse.html ''100% Lactobacillus Berliner Weisse.'' The Mad Fermentationist Blog, by Michael Tonsmeire. June 25, 2012. Retrieved 7/7/2015.]</ref>. Although the lowering of the wort's pH inhibits the proteolytic activity of ''Lacto'', it does not stop it completely, so continued exposure to ''Lactobacillus'' over time may still degrade the available head formation proteins. Additionally, ingredients that increase head retention such as unmalted chit, malted wheat, and carafoam have been used to help combat poor head retention in beers soured by ''Lactobacillus'' <ref name="Gail"></ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1105839682777578/?comment_id=1105942362767310&offset=0&total_comments=27&comment_tracking=%7B%22tn%22%3A%22R8%22%7D Conversation with Richard Preiss on MTF. 7/7/2015.]</ref>. Professional brewer [https://www.facebook.com/groups/MilkTheFunk/permalink/1105839682777578/ Kristen England of Bent Brewstillery] tested [http://www.mbaa.com/districts/MidSouth/mash/Documents/2014%20PDF%20Hop%20Product%20Applications%20Presentation.pdf?Mobile=1&Source=%2Fdistricts%2FMidSouth%2Fmash%2F_layouts%2Fmobile%2Fview.aspx%3FList%3D85ff6384-aa05-491f-8ef3-d2e9eea713f2%26View%3Da234a10f-469b-4edd-a8a9-9a96b00750ee%26CurrentPage%3D1 Hexa Iso Hop Extract] by dosing at 4 times the recommended dosage and found that it greatly increased head retention in a Berliner Weisse (3.5% abv, pH 3.1, TA ~1, BU 5), with a minor taste difference. Kristen recommends experimenting with lower dosages to avoid too much flavor impact.
Another method that has been reported to help with head retention when [[Sour Worting]] (kettle souring) is to add a pound of DME per 5 gallons of wort during the heat pasteurization process (after the wort has been soured with ''Lactobacillus''). One could also steep specialty grains such as wheat malt, chit malt, carafoam, or carapils, and add the extract into the kettle during the heat pasteurization or boiling process . This will add back head formation proteins that were lost during the ''Lacto'' fermentation <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1069228273105386/?comment_id=1069266549768225&offset=0&total_comments=24&comment_tracking=%7B%22tn%22%3A%22R8%22%7D Conversation with Gareth Young on MTF. 05/08/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1137179879643558/?comment_id=1137362989625247&offset=0&total_comments=8&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Paul Finney on MTF in regards to head retention of Berliner Weisse. 08/29/2015.]</ref>. See also [https://www.facebook.com/groups/MilkTheFunk/permalink/1069228273105386/?hc_location=ufi This discussion with Gareth Young on MTF].
[[File:Hexa Iso Foam Test.jpg|none|thumb|500px|Kristen England of Bent Brewstillery's Hexa Iso Hop Extract results (Hop Iso added to the left beer, nothing added to the right)]]