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Brewhouse Blog 10- What makes Ken tick? The intricacies of cooling a brew!

Brewing English-style beer is a pretty straight forward process. You mix grain with hot liquor (water) to make a mash which is very porridge-like in its consistency. You leave it for just over an hour and then run it off into a boiler, referred to as a copper or a kettle in brewery parlance. Our copper is made of stainless steel (Of course it is). You boil the wort (the liquid from the mash tun), add the hops of your dreams, in our case nearly exclusively English, cool it and collect it into a fermenting vessel, add yeast and…..Hey Presto! Four to seven days later you will have beer. However, much of this process is time and temperature critical (who said that it would be easy?).


Historically, cooling wort was a major obstacle for brewers. You cannot put yeast on hot wort as you will kill it. Yeast does not like heat. The time honoured cooling method was to run your hopped boiling wort into giant cooling trays where the large surface area would dissipate the heat quickly….but not that quick. Your precious wort is now vulnerable to any wild nasties, wild yeasts and impurities floating about unseen and undetected in the air. This may well result in off flavours. Folk tell me that this was a major contributory factor to the keg beer revolution of the 60’s where homogenized pasteurized beer nearly wiped out Real Ale altogether. And we have a lot to thank CAMRA for stopping that from happening.


If you want to see a brewery cooling tray there’s one at Woodchester Mansion, installed for the proposed brewery there. It never cooled any wort in anger, to the best of my knowledge.


Anyway, told you that to tell you this. The heat exchanger was invented. In the brewhouse we call it a paraflow in the same way that some folk refer to a vacuum cleaner as a Hoover (other brands are available) and it revolutionized the brewing process. You can cool your wort instantaneously allowing you the luxury of pitching your yeast as you pump through and thus avoid killing it. It works like this: The paraflow consists of a series of stainless steel plates squeezed tightly together. There are many feet of capillary channels in between each plate. On one side of each plate there is coolant (spring water in our case) and on the other hot wort.. As they pass though the plates from opposite ends, the wort cools down, and the coolant heats up. And because we’re using spring water we’ve heated it up and collected it in the Hot Liquor Tank (HLT) ready for the next brew – an ecological and environmental bonus and you lessen the chance of wrecking your beer with airborne nasties.


The paraflow has to be dismantled and cleaned on a regular basis. I did it a couple of weeks ago. It’s a 3 day job, or 2 if you put in a long shift. It’s painstakingly done one plate at a time. The plates will only work one way and you really need to focus and concentrate – and not get interrupted! Saddo that I am, I love doing this job. I lose myself in the process and, when after those long hours you press the plates back together, plumb it in and find it doesn’t leak, you feel great! And it’s time to go to the pub for a beer. You’ve earned this one, which makes it taste even better!