However, it wasn’t until a few months ago when I got chatting to a friend who did a stint for one of the ‘big boys’ did I realise how efficient they were.

Here is an extract from the e-mail:  I have omitted the name of the two brands:

“We produced ‘X’ and ‘Y’, but ‘Y’ was definitely the more extreme ‘macrobrew’ of the two. The malt bill was about 25% syrup and only 75% malt. The rest of the wort production process was fairly normal (we did also use alpha-acid extract in the kettle, but only about 10% of the hops used were extract, and I don’t find that too out of the ordinary).

“We tried to ferment it in less than 100 hours, but we looked at hours, gravity/AE, and total VKD count before calling fermentation done. Once the beer was between a certain AE and the total VKD was below 100ppm, we crashed the temperature, regardless of whether it was still fermenting (usually it wasn’t, in fact many times we crashed a batch because it had gone above our 120 hour maximum fermentation time).

“Once a batch had hit 2 deg. C, we centrifuged it and sent it to a maturation vessel. During this transfer we would add two things: first was a tetra- and hexa-iso-alpha-acid extract blend to bring the bitterness in spec (the kettle hop dosings were purposefully low, so we could add the extract and get the correct bitterness every time); and secondly, we would add ‘recovered beer’.

“This was beer that was filtered from the bottoms of the maturation vessels, pasteurised and then re-injected into subsequent batches; ‘Y’ could be up to 20% recovered beer, ‘X’ could be up to 5% (but recovered beer was a blend of those two brands – all of the bottoms were collected together in a series of tanks and it didn’t matter which brand they were, the mixtures were injected into either beer).

“Maturation was at -1 deg C and had a minimum of 5 days in residence.  After that time it was filtered. At this point the ‘Y’ was at about 8%-9% abv and the ‘X’ was at about 6.5%-7.5%. During my time there, we filtered them at this higher alcohol content and used (really cool and impressive!) blenders that would dilute a beer with de-aerated water and carbonate it as it was sent from the bright tank to packaging.

“These blenders measured AE, abv and carbonation and was able to keep the beer in a series of specifications as it was blended at a rate of 150 hectolitres per hour (so around 300 hectolitres an hour of diluted ‘Y’). The ‘Y’ was blended with de-aerated water to 4% and ‘X’ was diluted down to 5%, so the ‘Y’ was cut oftentimes by more than half, whereas the ‘X’ was only diluted by about 25%.

“One of the issues with high gravity brewing, which I remember from my classes at Brewing school was that high gravity brewing results in decreased head formation and retention, hexa-iso-alpha-acids increases head formation and retention (tetra- do as well, but to a lesser degree).

“Tetra- and hexa-iso-alpha-acids are also light-struck resistant, so it limited skunking (although our facility only did cans and kegs). In fact, before I left,  we had developed ‘Z’, which is exactly the same as regular ‘Y’, just blended to 4.5% or 5% instead of 4%, but also brewed almost entirely with a tetra- and hexa- blend.”.