12,395
edits
Milling: Difference between revisions
→Oxidation
| Line 208: | Line 208: | ||
=== Oxidation === | === Oxidation === | ||
[[File:Mill-on-cooler.jpg|thumb|right|Mill with base on top of a cooler mash tun]] | [[File:Mill-on-cooler.jpg|thumb|right|Mill with base on top of a cooler mash tun]] | ||
The grist begins to [[Oxidation|oxidize]] immediately upon milling (because the inside of the kernels are then exposed to air and moisture) and this can have a negative impact on the subsequent beer quality.<ref name=Kunze/><ref name=adb/><ref name=pasame>Pascoe HM, Ames JM, Chandra S. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-61-0203 Critical stages of the brewing process for changes in antioxidant activity and levels of phenolic compounds in ale.] ''J Am Soc Brew Chem.'' 2003;61(4):203–209.</ref> Therefore the time between milling and dough-in should be kept as short as possible.<ref name=golston>Golston AM. [https://www.mbaa.com/publications/tq/tqPastIssues/2021/Pages/TQ-58-1-0322-01.aspx The impact of barley lipids on the brewing process and final beer quality: A mini-review.] ''Tech Q Master Brew Assoc Am.'' 2021;58(1):43–51.</ref> | The grist begins to [[Oxidation|oxidize]] immediately upon milling (because the inside of the kernels are then exposed to air and moisture) and this can have a negative impact on the subsequent beer quality.<ref name=Kunze/><ref name=adb/><ref name=pasame>Pascoe HM, Ames JM, Chandra S. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-61-0203 Critical stages of the brewing process for changes in antioxidant activity and levels of phenolic compounds in ale.] ''J Am Soc Brew Chem.'' 2003;61(4):203–209.</ref><ref name=cheyni>Cheynier V. [https://academic.oup.com/ajcn/article-abstract/81/1/223S/4607504 Polyphenols in foods are more complex than often thought.] ''Am J Clin Nutr.'' 2005;81(1):223S–229S.</ref> Therefore the time between milling and dough-in should be kept as short as possible.<ref name=golston>Golston AM. [https://www.mbaa.com/publications/tq/tqPastIssues/2021/Pages/TQ-58-1-0322-01.aspx The impact of barley lipids on the brewing process and final beer quality: A mini-review.] ''Tech Q Master Brew Assoc Am.'' 2021;58(1):43–51.</ref> | ||
Modern commercial low oxygen breweries fill all areas containing milled grain with inert gas (CO<sub>2</sub> or N<sub>2</sub>) to prevent oxygen exposure.<ref name=Kunze/><ref name=bsp/><ref name=adb/><ref name=derouck/><ref name=golston/> Brewers looking to [[low oxygen brewing|preserve fresh grain flavor]] may do this simply by flowing inert gas into the bottom of the mash tun and milling directly into it, or by flushing the grist with inert gas after milling.<ref name=stephenson>Stephenson WH, Biawa JP, Miracle RE, Bamforth CW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2003.tb00168.x Laboratory-scale studies of the impact of oxygen on mashing.] ''J Inst Brew.'' 2003;109(3):273–283.</ref><ref name=mullerr>Muller R. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-53-0053 Use of 5,5’-dithiobis (2-nitrobenzoic acid) as a measure of oxidation during mashing.] ''J Am Soc Brew Chem.'' 1995;53(2):53–58.</ref><ref>[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=2&t=1025 CO2 purge of mash tun prior to underletting?] The Modern Brewhouse website. 2018. Accessed 2020.</ref><ref name="lob1394">[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=18&t=1394 Milling into mash tun.] The Modern Brewhouse website. 2019. Accessed 2020.</ref> Purging a mostly covered mash tun at 1–2 psi for about 10 minutes has been shown to effectively remove the vast majority of oxygen in the vessel.<ref>[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=11&t=751 Purging grist in the tun.] The Modern Brewhouse website. 2018. Accessed 2020.</ref> A regulator may start to freeze up and/or significantly chill the mash tun parts, causing dough-in temperature to be too low. A fix for that is to get a cheap heat lamp or hair dryer and point it at your regulator.<ref name="lob1394"/> Dry ice can also be used to purge: put the dry ice in a jar with water and connect it with tubing to the mash tun. Note that flushing with inert gas during the actual milling process appears not to be entirely critical, as oxidation does not occur immediately (at least with regard to [[lipids]]).<ref name=wackerbauer>Wackerbauer K, Meyna S, Marre S. [http://themodernbrewhouse.com/wp-content/uploads/2017/04/174-178.pdf Hydroxy fatty acids as indicators for ageing and the influence of oxygen in the brewhouse on the flavour stability of beer.] ''Monatsschrift Brauwiss.'' 2003;56(9/10):174–178.</ref> | Modern commercial low oxygen breweries fill all areas containing milled grain with inert gas (CO<sub>2</sub> or N<sub>2</sub>) to prevent oxygen exposure.<ref name=Kunze/><ref name=bsp/><ref name=adb/><ref name=derouck/><ref name=golston/> Brewers looking to [[low oxygen brewing|preserve fresh grain flavor]] may do this simply by flowing inert gas into the bottom of the mash tun and milling directly into it, or by flushing the grist with inert gas after milling.<ref name=stephenson>Stephenson WH, Biawa JP, Miracle RE, Bamforth CW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2003.tb00168.x Laboratory-scale studies of the impact of oxygen on mashing.] ''J Inst Brew.'' 2003;109(3):273–283.</ref><ref name=mullerr>Muller R. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-53-0053 Use of 5,5’-dithiobis (2-nitrobenzoic acid) as a measure of oxidation during mashing.] ''J Am Soc Brew Chem.'' 1995;53(2):53–58.</ref><ref>[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=2&t=1025 CO2 purge of mash tun prior to underletting?] The Modern Brewhouse website. 2018. Accessed 2020.</ref><ref name="lob1394">[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=18&t=1394 Milling into mash tun.] The Modern Brewhouse website. 2019. Accessed 2020.</ref> Purging a mostly covered mash tun at 1–2 psi for about 10 minutes has been shown to effectively remove the vast majority of oxygen in the vessel.<ref>[http://www.themodernbrewhouse.com/forum/viewtopic.php?f=11&t=751 Purging grist in the tun.] The Modern Brewhouse website. 2018. Accessed 2020.</ref> A regulator may start to freeze up and/or significantly chill the mash tun parts, causing dough-in temperature to be too low. A fix for that is to get a cheap heat lamp or hair dryer and point it at your regulator.<ref name="lob1394"/> Dry ice can also be used to purge: put the dry ice in a jar with water and connect it with tubing to the mash tun. Note that flushing with inert gas during the actual milling process appears not to be entirely critical, as oxidation does not occur immediately (at least with regard to [[lipids]]).<ref name=wackerbauer>Wackerbauer K, Meyna S, Marre S. [http://themodernbrewhouse.com/wp-content/uploads/2017/04/174-178.pdf Hydroxy fatty acids as indicators for ageing and the influence of oxygen in the brewhouse on the flavour stability of beer.] ''Monatsschrift Brauwiss.'' 2003;56(9/10):174–178.</ref> | ||