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Lipids: Difference between revisions
→Lipid transformations
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[[File:Lipase-reaction.gif|frame|Enzymatic degradation by lipase]] | [[File:Lipase-reaction.gif|frame|Enzymatic degradation by lipase]] | ||
Lipase is the enzyme responsible for the large increase in FFAs during mashing. It breaks apart TAGs into its components of glycerol and FFAs.<ref name=schwarzp>Schwarz P, Stanley P, Solberg S. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-60-0107 Activity of lipase during mashing.] ''J Am Soc Brew Chem.'' 2002;60(3):107–109.</ref><ref name=adb>Narziss L, Back W, Gastl M, Zarnkow M. [[Library|''Abriss der Bierbrauerei.'']] 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.</ref> Besides barley, [[rice]] also contains lipase.<ref name=schwarzp/> Lipase is fairly stable at the range of temperatures used for mashing barley (up to around 158°F/70°C), so it is active throughout the duration of mashing, continually increasing the level of free fatty acids.<ref name=schwarzp/><ref name=golston/><ref name=cozzolino/><ref name=adb/> | Lipase is the enzyme responsible for the large increase in FFAs during mashing. It breaks apart TAGs into its components of glycerol and FFAs.<ref name=schwarzp>Schwarz P, Stanley P, Solberg S. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-60-0107 Activity of lipase during mashing.] ''J Am Soc Brew Chem.'' 2002;60(3):107–109.</ref><ref name=adb>Narziss L, Back W, Gastl M, Zarnkow M. [[Library|''Abriss der Bierbrauerei.'']] 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.</ref> Besides barley, [[rice]] also contains lipase.<ref name=schwarzp/> Lipase is fairly stable at the range of temperatures used for mashing barley (up to around 158°F/70°C), so it is active throughout the duration of mashing, continually increasing the level of free fatty acids.<ref name=schwarzp/><ref name=golston/><ref name=cozzolino/><ref name=adb/><ref name=baedec>Baert JJ, De Clippeleer J, Hughes PS, De Cooman L, Aerts G. [https://www.themodernbrewhouse.com/wp-content/uploads/2017/03/Baert-Aldehyden.pdf On the origin of free and bound staling aldehydes in beer.] ''J Agric Food Chem.'' 2012;60(46):11449–11472.</ref> | ||
Lipoxygenases (LOX) occur in two forms, called LOX-1 and LOX-2.<ref name=bmp1>Davies N. Malts. In: Bamforth CW, ed. [[Library|''Brewing Materials and Processes: A Practical Approach to Beer Excellence.'']] Academic Press; 2016.</ref><ref name=adb/> These enzymes oxidize fatty acids during the brewing process, whether free or still bound to glycerol.<ref name=arts/><ref name=kunze/><ref name=golston/><ref name=garbe>Garbe LA, Barbosa de Almeida R, Nagel R, Wackerbauer K, Tressl R. [https://pubs.acs.org/doi/abs/10.1021/jf051993t Dual positional and stereospecificity of lipoxygenase isoenzymes from germinating barley (green malt): Biotransformation of free and esterified linoleic acid.] ''J Agric Food Chem.'' 2006;54(3):946–955.</ref> Under its preferred conditions (below 60°C and relatively high mash pH), LOX-1 works very quickly and remains active until the temperature is increased.<ref name=arts/> In this case, even a relatively small amount of LOX can oxidize a large proportion of malt lipids during the mash.<ref name=norja>Kaukovirta-Norja A, Laakso S, Reinikainen P, Olkku J. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1993.tb01179.x Lipolytic and oxidative changes of barley lipids during malting and mashing.] ''J Inst Brew.'' 1993;99:395–403.</ref><ref name=bamenz>Bamforth CW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1999.tb00025.x Enzymic and non‐enzymic oxidation in the brewhouse: A theoretical consideration.] ''J Inst Brew.'' 1999;105(4):237–242.</ref> Fortunately we have ways to minimize the activity of LOX during the mash (see below). LOX-2 is significantly less thermostable than LOX-1; thus, its contribution to FA oxidation during mashing is considered negligible.<ref name=golston/> Although they don't get as much attention as LOX, other enzymes in the wort are also involved with lipid oxidation, such as hydroperoxide lyase, which is partly responsible for converting oxidized lipids to E2N.<ref name=kuroda/><ref name=lewbam/><ref name=mashing/><ref name=cargon>Carvalho DO, Gonçalves LM, Guido LF. [https://ift.onlinelibrary.wiley.com/doi/abs/10.1111/1541-4337.12218 Overall antioxidant properties of malt and how they are influenced by the individual constituents of barley and the malting process.] ''Compr Rev Food Sci Food Saf.'' 2016;15(5):927–943.</ref><ref name=bamlen>Bamforth CW, Lentini A. The flavor instability of beer. In: Bamforth CW, ed. [[Library|''Beer: A Quality Perspective.'']] Academic Press; 2009:85–109.</ref> | Lipoxygenases (LOX) occur in two forms, called LOX-1 and LOX-2.<ref name=bmp1>Davies N. Malts. In: Bamforth CW, ed. [[Library|''Brewing Materials and Processes: A Practical Approach to Beer Excellence.'']] Academic Press; 2016.</ref><ref name=adb/> These enzymes oxidize fatty acids during the brewing process, whether free or still bound to glycerol.<ref name=arts/><ref name=kunze/><ref name=golston/><ref name=garbe>Garbe LA, Barbosa de Almeida R, Nagel R, Wackerbauer K, Tressl R. [https://pubs.acs.org/doi/abs/10.1021/jf051993t Dual positional and stereospecificity of lipoxygenase isoenzymes from germinating barley (green malt): Biotransformation of free and esterified linoleic acid.] ''J Agric Food Chem.'' 2006;54(3):946–955.</ref> Under its preferred conditions (below 60°C and relatively high mash pH), LOX-1 works very quickly and remains active until the temperature is increased.<ref name=arts/> In this case, even a relatively small amount of LOX can oxidize a large proportion of malt lipids during the mash.<ref name=norja>Kaukovirta-Norja A, Laakso S, Reinikainen P, Olkku J. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1993.tb01179.x Lipolytic and oxidative changes of barley lipids during malting and mashing.] ''J Inst Brew.'' 1993;99:395–403.</ref><ref name=bamenz>Bamforth CW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1999.tb00025.x Enzymic and non‐enzymic oxidation in the brewhouse: A theoretical consideration.] ''J Inst Brew.'' 1999;105(4):237–242.</ref> Fortunately we have ways to minimize the activity of LOX during the mash (see below). LOX-2 is significantly less thermostable than LOX-1; thus, its contribution to FA oxidation during mashing is considered negligible.<ref name=golston/> Although they don't get as much attention as LOX, other enzymes in the wort are also involved with lipid oxidation, such as hydroperoxide lyase, which is partly responsible for converting oxidized lipids to E2N.<ref name=kuroda/><ref name=lewbam/><ref name=mashing/><ref name=cargon>Carvalho DO, Gonçalves LM, Guido LF. [https://ift.onlinelibrary.wiley.com/doi/abs/10.1111/1541-4337.12218 Overall antioxidant properties of malt and how they are influenced by the individual constituents of barley and the malting process.] ''Compr Rev Food Sci Food Saf.'' 2016;15(5):927–943.</ref><ref name=bamlen>Bamforth CW, Lentini A. The flavor instability of beer. In: Bamforth CW, ed. [[Library|''Beer: A Quality Perspective.'']] Academic Press; 2009:85–109.</ref> | ||