Editing Lipids (section)

===Limiting LOX activity===
When its activity is properly controlled, lipoxygenase (LOX) is a relatively small part of the potential contributors to beer staling.<ref name=bmp1/><ref name=mashing/><ref name=guicur>Guido LF, Curto AF, Boivin P, Benismail N, Gonçalves CR, Barros AA. [https://pubs.acs.org/doi/abs/10.1021/jf0623079 Correlation of malt quality parameters and beer flavor stability:  multivariate analysis.] ''J Agric Food Chem.'' 2007;55(3):728–733.</ref><ref name=kanbam>Kanauchi M, Bamforth CW. [https://www.themodernbrewhouse.com/wp-content/uploads/2019/02/BrewingScience_bamforth_82-84.pdf A Challenge in the study of flavour instability.] ''BrewingScience - Monatsschrift Brauwiss.'' 2018;71(Sept/Oct):82–84.</ref> There are several ways that brewers can reduce  LOX activity in the mash:
* '''Low oxygen''' - Antioxidants and brewing methods that lower the oxygen ingress into wort reduce the action of LOX.<ref name=kunze/><ref name=adb/><ref name=derouck/><ref name=derouckg>De Rouck G, Jaskula B, De Causmaecker B, et al. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-2013-0113-01 The influence of very thick and fast mashing conditions on wort composition.] ''J Am Soc Brew Chem.'' 2013;71(1):1–14.</ref><ref name=golston/> This is redundant because we must keep the wort low oxygen in order to have any hope of avoiding massive oxidation damage to lipids and other compounds. See [[Low oxygen brewing]].
* '''Low mash pH''' - LOX has a relatively high optimal pH range, so lowering the mash pH reduces its activity by around 50% or more compared to higher pH.<ref name=bamlen/><ref name=kunze/><ref name=golston/><ref name=derouck/> Keeping mash pH under 5.8 is beneficial, and pH 5.4 or lower is preferred (measured at room temperature).<ref name=bsp/><ref name=derouck/><ref name=golston/><ref name=adb/><ref name=poyri>Pöyri S, Mikola M, Sontag-Strohm T, Kaukovirta-Norja A, Home S. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2002.tb00550.x The formation and hydrolysis of barley malt gel-protein under different mashing conditions.] ''J Inst Brew.'' 2002;108(2):261–267.</ref> See [[Brewing pH]].
* '''High mash temperature''' - Mashing in at a temperature of at least 140°F (60°C) will reduce (but not eliminate) LOX activity since most of it is rapidly denatured.<ref name=poyri/><ref name=golston/><ref name=kunze/><ref name=wackerbauer/><ref name=mashing/> Mash-in temperatures of 144–145°F (62–63°C) are often recommended (avoid lower rests).<ref name=adb/><ref name=derouck/> See [[Mashing]].
* '''Short mash duration''' - Less time spent mashing, especially any time spent under 149°F (65°C) helps to limit LOX activity.<ref name=kunze/> This is one of the reasons why the high temperature and short duration of the ''Hoch-Kurz'' step mashing schedule is beneficial.
* '''Coarse crush''' - Fine milling causes more damage to the barley embryo and acrospires, which increases wort lipid and LOX levels.<ref name=golston/> Therefore, a more coarse crush is suggested to help reduce lipid oxidation.<ref name=adb/><ref name=kunze/><ref name=derouck>De Rouck G, Jaskula-Goiris B, De Causmaecker B, et al. [https://www.brewingscience.de/index.php?tpl=table_of_contents&year=2013&edition=0001%252F0002&article=82374 The impact of wort production on the flavour quality and stability of pale lager beer.] ''BrewingScience.'' 2013;66(1/2):1–11.</ref> Best practices such as purging the oxygen from the grain and milling closer to mash-in can be helpful as well.<ref name=adb/><ref name=golston/> See [[Milling]].
* '''Null-LOX malt''' - Brewers may utilize a malt labeled as null-LOX or LOX-less, which has been bred to contain zero LOX enzymes toward the end of germination.<ref name=kuroda/><ref name=mashing/><ref name=bmp1/><ref name=derouck/><ref name=derouckg/> This is an effective approach because such malt has been shown to produce lower levels of oxidized lipid products, along with corresponding increases to foam and flavor stability.<ref name=golston/><ref>Hoki T, Saito W, Iimure T, et al. [https://www.sciencedirect.com/science/article/abs/pii/S0733521018303825 Breeding of lipoxygenase-1-less malting barley variety 'SouthernStar' and evaluation of malting and brewing quality.] ''J Cereal Sci.'' 2018;83:83–89.</ref><ref>Oozeki M, Sotome T, Haruyama N, et al. [https://www.jstage.jst.go.jp/article/jsbbs/advpub/0/advpub_16104/_article/-char/ja/ The two-row malting barley cultivar 'New Sachiho Golden' with null lipoxygenase-1 improves flavor stability in beer and was developed by marker-assisted selection.] ''Breed Sci.'' 2017:16104.</ref> However, the availability of null-LOX malt varieties is very limited, which may restrict its usage. See [[Malt]].
* '''Malt color''' - More-highly-kilned malt contains comparatively lower amounts of the LOX enzymes since the enzyme is destroyed to a greater extent by higher temperatures.<ref name=kunze/><ref name=norja/> In fact, LOX activity may decrease by 30–99.5% during the kilning process.<ref name=golston/> However, evidence suggests that higher kilning temperature may actually lead to higher levels of staling compounds in the wort (despite lower LOX activity).<ref name=guidol/><ref name=kuroda/><ref name=bmp1/> This is because the warmer kilning conditions promote lipid oxidization during kilning, creating a larger amount of staling compounds (nonenal potential) in the malt. On the other hand, it has been shown that modest additions of highly-kilned malt (i.e. 15% melanoidin, 10% caramel, or 1% black malt) decrease LOX activity in the mash. The increased [[melanoidins|melanoidin]] content of darker malt is believed to inhibit LOX, and the melanoidins also possess antioxidant capacity.<ref name=sovrano/>
*'''Storage time''' - LOX activity declines over time as malt is stored.<ref name=adb/><ref name=golston/> However, oxidation products increase during malt storage.<ref name=adb/> Use fresh ingredients!