Protein: Difference between revisions

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 Excessive protein degradation is unnecessary and undesirable.<ref name=kunze/> Too much proteolysis may cause the development of undesirable flavors and color, reduced foam, and a thinner mouth feel.<ref name=osman/><ref name=lund/> Brewers can manipulate the amount of protein degradation mainly through control of the mash temperature and duration. At mash temperatures around 113–131°F (45–55°C), proteins are most thoroughly degraded, producing small protein fragments and amino acids. A rest in this temperature range (i.e. a "protein rest") should be avoided ''except'' when using poorly-modified malts.<ref name=kunze/> At higher mash temperatures such as 140–158°F (60–70°C), mostly larger protein fragments are formed, which are responsible for [[foam]] stability and mouth feel. Due to their heat-sensitivity, proteinases generally begin to inactivate at temperatures above 140°F (60°C). Above 158°F (70°C), they are inactivated more quickly, although they retain activity for about 15–20 minutes or possibly longer.<ref name=jones/><ref name=klose/><ref name=poyri/> The Hoch-Kurz [[mashing]] process can be implemented in order to restrict the activity of the endopeptidases and thus increase the percentage of larger peptides while retaining sufficient amino acid formation through the activity of the more thermostable carboxypeptidases.<ref name=sacher/><ref name=derouck/><ref name=cven>Cvengroschová M, Šepel'ová G, Šmogrovičová D. [https://www.themodernbrewhouse.com/wp-content/uploads/2017/04/128-131.pdf Effect of mashing-in temperature on free amino nitrogen concentration and foam stability of beer.] ''Monatsschrift Brauwiss.'' 2003;56(7/8):128–131.</ref> The proteases are stable enough that even with these relatively high mashing temperatures, the total soluble protein level cannot drop below a value that was already predetermined by the malt quality.<ref name=adb/> Proteolysis doesn't fully stop until around 176°F (80°C), well above mash temperature.
-To a lesser extent, [[brewing pH|mash pH]], grist to liquor ratio, and other factors can influence the activity of proteases and solubility of polypeptides.<ref name=picariello/> The activity of cysteine proteases (and therefore protein degradation) is inhibited by mash oxidation and stimulated by reducing agents.<ref name=benesova/><ref name=poyri/><ref name=sacher>Sacher B, Becker T, Narziss L. [http://www.lowoxygenbrewing.com/wp-content/uploads/2017/04/pkjdf.pdf Some reflections on mashing – Part 1.] ''Brauwelt International.'' 2016;5:309-311.</ref><ref name=jonesbl>Jones BL. [https://www.sciencedirect.com/science/article/abs/pii/S073352100500055X Endoproteases of barley and malt.] ''J Cereal Sci.'' 2005;42(2):139–156.</ref> Metalloproteases are inhibited by chelators (especially those with affinity for [[zinc]]).<ref name=benesova/><ref>Rizvi SMH, Beattie A, Rossnagel B, Scoles G. [https://www.researchgate.net/publication/215493909_Thermostability_of_Barley_Malt_Proteases_in_Western_Canadian_Two-Row_Malting_Barley Thermostability of barley malt proteases in western Canadian two-row malting barley] ''Cereal Chem.'' 2011;88(6):609–613</ref> Protease activity generally increases as the mash pH approaches 5.0 (see [[Brewing pH]]).<ref name=adb/> Protein degradation is greater in thicker mashes because enzyme activity is protected from thermal inactivation due to a protective colloid effect.<ref name=adb/> Finer grist appears to release amino acids into the wort more quickly, but ultimately it does not affect the level of protein degradation.<ref name=kuhbeck>Kühbeck F, Dickel T, Krottenthaler M, et al.
+To a lesser extent, [[brewing pH|mash pH]], grist to liquor ratio, and other factors can influence the activity of proteases and solubility of polypeptides.<ref name=picariello/> The activity of cysteine proteases (and therefore protein degradation) is inhibited by mash oxidation and stimulated by reducing agents.<ref name=benesova/><ref name=poyri/><ref name=sacher>Sacher B, Becker T, Narziss L. [http://www.themodernbrewhouse.com/wp-content/uploads/2017/04/pkjdf.pdf Some reflections on mashing – Part 1.] ''Brauwelt International.'' 2016;5:309-311.</ref><ref name=jonesbl>Jones BL. [https://www.sciencedirect.com/science/article/abs/pii/S073352100500055X Endoproteases of barley and malt.] ''J Cereal Sci.'' 2005;42(2):139–156.</ref> Metalloproteases are inhibited by chelators (especially those with affinity for [[zinc]]).<ref name=benesova/><ref>Rizvi SMH, Beattie A, Rossnagel B, Scoles G. [https://www.researchgate.net/publication/215493909_Thermostability_of_Barley_Malt_Proteases_in_Western_Canadian_Two-Row_Malting_Barley Thermostability of barley malt proteases in western Canadian two-row malting barley] ''Cereal Chem.'' 2011;88(6):609–613</ref> Protease activity generally increases as the mash pH approaches 5.0 (see [[Brewing pH]]).<ref name=adb/> Protein degradation is greater in thicker mashes because enzyme activity is protected from thermal inactivation due to a protective colloid effect.<ref name=adb/> Finer grist appears to release amino acids into the wort more quickly, but ultimately it does not affect the level of protein degradation.<ref name=kuhbeck>Kühbeck F, Dickel T, Krottenthaler M, et al.
 [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2005.tb00690.x Effects of mashing parameters on mash β-glucan, FAN and soluble extract levels.] ''J Inst Brew.'' 2005;111(3):316–327.</ref>