Editing Brewing (section)

==Boiling==

After mashing, the beer [[wort]] is boiled with [[hops]] (and other flavourings if used) in a large tank known as a "copper" or brew kettle – though historically the mash vessel was used and is still in some small breweries.<ref>{{cite book |url=https://books.google.com/books?id=7eYLjJp0y7UC&pg=PA5 |title=Beer in the Middle Ages and the Renaissance |page=5 |author=Richard W. Unger |publisher=University of Pennsylvania Press |year=2007 |access-date=15 November 2012 |isbn=978-0812203745 |archive-url=https://web.archive.org/web/20160603192722/https://books.google.com/books?id=7eYLjJp0y7UC&pg=PA5 |archive-date=3 June 2016 |url-status=live }}</ref> The boiling process is where chemical reactions take place,<ref name="Fosters" /> including [[sterilization (microbiology)|sterilization]] of the wort to remove unwanted bacteria, releasing of hop flavours, bitterness and aroma compounds through [[isomerization]], stopping of enzymatic processes, [[Precipitation (chemistry)|precipitation]] of proteins, and concentration of the wort.<ref>{{cite book |url=https://books.google.com/books?id=ogXc9xTTCVsC&pg=PA63 |title=Froth!: The Science of Beer |page=63 |author=Mark Denny |publisher=JHU Press |date=6 May 2009 |access-date=15 November 2012 |isbn=9780801895692 |archive-url=https://web.archive.org/web/20160624144735/https://books.google.com/books?id=ogXc9xTTCVsC&pg=PA63 |archive-date=24 June 2016 |url-status=live }}</ref><ref name="Bamforth 2011">{{cite book |url=https://books.google.com/books?id=gYVLHMmplRcC&pg=PA141 |title=The Oxford Companion to Beer |pages=141–142 |author=Charles W. Bamforth |access-date=15 November 2012 |isbn=9780195367133 |date=9 September 2011 |publisher=Oxford University Press, USA |archive-url=https://web.archive.org/web/20160529073112/https://books.google.com/books?id=gYVLHMmplRcC&pg=PA141 |archive-date=29 May 2016 |url-status=live }}</ref> Finally, the vapours produced during the boil volatilise [[off-flavour]]s, including [[dimethyl sulfide]] precursors.<ref name="Bamforth 2011"/> The boil is conducted so that it is even and intense – a continuous "rolling boil".<ref name="Bamforth 2011" /> The boil on average lasts between 45 and 90 minutes, depending on its intensity, the hop addition schedule, and volume of water the brewer expects to evaporate.<ref>{{cite book|url=https://books.google.com/books?id=i__29xn-8t4C&pg=PA47|title=Essays in Brewing Science|page=47|author1=Michael J. Lewis|author2=Charles W. Bamforth|publisher=Springer|date=4 October 2006|access-date=15 November 2012|isbn=9780387330105|archive-url=https://web.archive.org/web/20160506071219/https://books.google.com/books?id=i__29xn-8t4C&pg=PA47|archive-date=6 May 2016|url-status=live}}</ref> At the end of the boil, solid particles in the hopped wort are separated out, usually in a vessel called a "whirlpool".<ref name="Hornsey 2004" />

===Brew kettle or copper===
[[File:Brasserie La Choulette 12-11-2006.jpg|thumb|Brew kettles at Brasserie La Choulette in France]]

Copper is the traditional material for the boiling vessel for two main reasons: firstly because copper transfers heat quickly and evenly; secondly because the bubbles produced during boiling, which could act as an insulator against the heat, do not cling to the surface of copper, so the wort is heated in a consistent manner.<ref name="Brew p272">{{cite book |url=https://books.google.com/books?id=cr9Pv0gefCQC&pg=PA272 |title=Brewing |page=272 |author1=Michael Lewis |author2=Tom W. Young |publisher=Springer |year=2002 |isbn=9780306472749 |access-date=19 November 2015 |archive-url=https://web.archive.org/web/20160511062855/https://books.google.com/books?id=cr9Pv0gefCQC&pg=PA272&dq |archive-date=11 May 2016 |url-status=live }}</ref> The simplest boil kettles are direct-fired, with a burner underneath. These can produce a vigorous and favourable boil, but are also apt to scorch the wort where the flame touches the kettle, causing caramelisation and making cleanup difficult. Most breweries use a steam-fired kettle, which uses steam jackets in the kettle to boil the wort.<ref name="Bamforth 2011" /> Breweries usually have a boiling unit either inside or outside of the kettle, usually a tall, thin cylinder with vertical tubes, called a calandria, through which wort is pumped.<ref name="Hampson 2011">{{cite book|url=https://books.google.com/books?id=gYVLHMmplRcC&pg=PA201|title=The Oxford Companion to Beer|page=201|author=Tim Hampson|publisher=Oxford University Press|date=9 September 2011|isbn=9780195367133|archive-url=https://web.archive.org/web/20160502054817/https://books.google.com/books?id=gYVLHMmplRcC&pg=PA201|archive-date=2 May 2016|url-status=live}}</ref>

===Whirlpool===

At the end of the boil, solid particles in the hopped wort are separated out, usually in a vessel called a "whirlpool" or "settling tank".<ref name="Hornsey 2004" /><ref name="Klimovitz 2011"/> The whirlpool was devised by Henry Ranulph Hudston while working for the [[Molson Brewery]] in 1960 to utilise the so-called [[tea leaf paradox]] to force the denser solids known as "trub" (coagulated proteins, vegetable matter from hops) into a cone in the centre of the whirlpool tank.<ref>{{cite journal |author=W. Reed |date=1969 |title=The Whirlpool |journal=International Brewers' Journal |volume=105 |issue=2 |page=41 }}</ref><ref>{{cite web|url=http://www.mooseheadbeeracademy.com/teacups-albert-einstein-and-henry-hudston-moosehead-brewmaster/|work=mooseheadbeeracademy.com|title=Teacups, Albert Einstein, and Henry Hudston|author=Darrell Little|date=20 March 2013|access-date=7 December 2016|archive-url=https://web.archive.org/web/20170305002814/http://www.mooseheadbeeracademy.com/teacups-albert-einstein-and-henry-hudston-moosehead-brewmaster/|archive-date=5 March 2017|url-status=live}}</ref><ref name="Bamforth 2009">{{cite book|url=https://books.google.com/books?id=V3Sr4bbTH5oC&pg=PT170|page=170|title=Beer: Tap into the Art and Science of Brewing|author=Charles Bamforth|publisher=Oxford University Press|date=6 March 2009|isbn=9780199756360|access-date=7 December 2016|archive-url=https://web.archive.org/web/20191223130933/https://books.google.com/books?id=V3Sr4bbTH5oC&pg=PT170|archive-date=23 December 2019|url-status=live}}</ref> Whirlpool systems vary: smaller breweries tend to use the brew kettle, larger breweries use a separate tank,<ref name="Klimovitz 2011"/> and design will differ, with tank floors either flat, sloped, conical or with a cup in the centre.<ref>{{cite book|url=https://books.google.com/books?id=ciA6-YMTI-UC&pg=PA517|pages=517–518|title=Malting and Brewing Science: Hopped Wort and Beer|author=Tom W. Young|publisher=Springer|year=1982|isbn=9780834216846|archive-url=https://web.archive.org/web/20160506011544/https://books.google.com/books?id=ciA6-YMTI-UC&pg=PA517|archive-date=6 May 2016|url-status=live}}</ref> The principle in all is that by swirling the wort the [[centripetal force]] will push the trub into a cone at the centre of the bottom of the tank, where it can be easily removed.<ref name="Klimovitz 2011">{{cite book|url=https://books.google.com/books?id=oWQdjnVo2B0C&pg=PA841|page=841|author=Ray Klimovitz|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=9 September 2011|isbn=9780199912100|archive-url=https://web.archive.org/web/20160527011846/https://books.google.com/books?id=oWQdjnVo2B0C&pg=PA841|archive-date=27 May 2016|url-status=live}}</ref>

===Hopback===

A hopback is a traditional additional chamber that acts as a sieve or filter by using whole [[hops]] to clear debris (or "[[Trub (brewing)|trub]]") from the unfermented (or "green") [[wort]],<ref>{{cite book|url=https://books.google.com/books?id=SCg0ct2JKSoC&pg=PT25|page=25|title=Beer: A Gauge for Enthusiasts|author=Greg Duncan Powell|publisher=Allen & Unwin|date=2010|isbn=9781741968132|archive-url=https://web.archive.org/web/20191219200622/https://books.google.com/books?id=SCg0ct2JKSoC&pg=PT25|archive-date=19 December 2019|url-status=live}}</ref> as the whirlpool does, and also to increase hop aroma in the finished beer.<ref>{{cite book|url=https://books.google.com/books?id=gYVLHMmplRcC&pg=PA540|page=540|author=Chad Michael Yakobson|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=9 September 2011|isbn=9780195367133|archive-url=https://web.archive.org/web/20160604055338/https://books.google.com/books?id=gYVLHMmplRcC&pg=PA540|archive-date=4 June 2016|url-status=live}}</ref><ref>{{cite book|url=https://books.google.com/books?id=MonpQW63TKcC&pg=PA127|title=Brewing|page=127|author=Ian Hornsey|publisher=Royal Society of Chemistry|date=2013|isbn=9781849736022|archive-url=https://web.archive.org/web/20160509224128/https://books.google.com/books?id=MonpQW63TKcC&pg=PA127|archive-date=9 May 2016|url-status=live}}</ref> It is a chamber between the brewing kettle and wort chiller. Hops are added to the chamber, the hot wort from the kettle is run through it, and then immediately cooled in the wort chiller before entering the fermentation chamber. Hopbacks utilizing a sealed chamber facilitate maximum retention of volatile hop aroma compounds that would normally be driven off when the hops contact the hot wort.<ref>{{cite book|url=https://books.google.com/books?id=NB8NAQAAIAAJ&pg=PA23|page=23|title=The Brewing Industry: A Guide to Historical Records|author=Peter Mathias|publisher=Manchester University Press|date=1 January 1990|isbn=9780719030321|archive-url=https://web.archive.org/web/20160617050459/https://books.google.com/books?id=NB8NAQAAIAAJ&pg=PA23|archive-date=17 June 2016|url-status=live}}</ref> While a hopback has a similar filtering effect as a whirlpool, it operates differently: a whirlpool uses centrifugal forces, a hopback uses a layer of whole hops to act as a filter bed. Furthermore, while a whirlpool is useful only for the removal of pelleted hops (as flowers do not tend to separate as easily), in general hopbacks are used only for the removal of whole flower hops (as the particles left by pellets tend to make it through the hopback).<ref>{{cite book |url=https://books.google.com/books?id=ciA6-YMTI-UC&pg=PA516 |title=Malting and Brewing Science: Hopped Wort and Beer |pages=516–517 |author1=J.S. Hough |author2=D.E. Briggs |author3=R. Stevens |author4=Tom W. Young |publisher=Springer |date=31 August 1982 |access-date=31 July 2012 |isbn=9780834216846 |archive-url=https://web.archive.org/web/20160603232406/https://books.google.com/books?id=ciA6-YMTI-UC&pg=PA516&lpg=PA516 |archive-date=3 June 2016 |url-status=live }}</ref> The hopback has mainly been substituted in modern breweries by the whirlpool.<ref>{{cite book|url=https://books.google.com/books?id=oWQdjnVo2B0C&pg=PA453|page=453|author=Paul Buttrick|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=9 September 2011|isbn=9780199912100|archive-url=https://web.archive.org/web/20160514132504/https://books.google.com/books?id=oWQdjnVo2B0C&pg=PA453|archive-date=14 May 2016|url-status=live}}</ref>

===Wort cooling===
After the whirlpool, the wort must be brought down to fermentation temperatures {{convert|20|-|26|C|F}}<ref name="Van den Steen" /> before yeast is added. In modern breweries this is achieved through a plate [[heat exchanger]].<ref name=Plate>{{cite book |url=https://books.google.com/books?id=0os_gIvG_ccC&pg=PA312|page=312|title=Handbook of Brewing|editor=William Hardwick|publisher=CRC Press|date= 15 Nov 1994|isbn=978-0-8493-9035-7 }}</ref> A plate heat exchanger has sereral ridged plates, which form two separate paths. The wort is pumped into the heat exchanger, and goes through every other gap between the plates.<ref name=Plate/> The cooling medium, usually water from a [[cold liquor tank]], goes through the other gaps. The ridges in the plates ensure turbulent flow.<ref>{{cite web|url=https://theengineeringmindset.com/how-plate-heat-exchangers-work/|work=theengineeringmindset.com|title=How Plate Heat Exchangers Work|author=Paul Evans|date=5 July 2019}}</ref>  A good heat exchanger can drop {{Convert|95|°C}} wort to {{Convert|20|°C}} while warming the cooling medium from about {{Convert|10|°C}} to {{Convert|80|°C}}. The last few plates often use a cooling medium which can be cooled to below the [[freezing point]], which allows a finer control over the wort-out temperature, and also enables cooling to around {{Convert|10|°C}}. After cooling, oxygen is often dissolved into the wort to revitalize the yeast and aid its reproduction.<ref>{{cite web|url= https://byo.com/article/aerating-wort-techniques/|work=byo.com|title=Aerating Wort Techniques|author=Jon Stika|year=2009}}</ref> 

While boiling, it is useful to recover some of the energy used to boil the wort. On its way out of the brewery, the steam created during the boil is passed over a coil through which unheated water flows. By adjusting the rate of flow, the output temperature of the water can be controlled. This is also often done using a plate heat exchanger. The water is then stored for later use in the next mash, in equipment cleaning, or wherever necessary.<ref name="Kunze 2004">{{cite book|author=Wolfgang Kunze |date=2004 |title=Technology Brewing and Malting|url=https://archive.org/details/technologybrewin00kunz |url-access=limited |publisher=VLB Berlin|isbn=3-921690-49-8|page=[https://archive.org/details/technologybrewin00kunz/page/n299 302]}}</ref> Another common method of energy recovery takes place during the wort cooling. When cold water is used to cool the wort in a heat exchanger, the water is significantly warmed. In an efficient brewery, cold water is passed through the heat exchanger at a rate set to maximize the water's temperature upon exiting. This now-hot water is then stored in a hot water tank.<ref name="Kunze 2004" />