A visit to Guinness brewery

Back in Dublin for the first time since 1911 I finally got to go round the Guinness brewery at St James's Gate. 

Diageo own "46-50" breweries, of which only five brew draught Guinness, most making the far superior Foreign Extra Stout (FES). It has a lot of diacetyl though  (>250ppb!), which just shows that it's not always a bad thing. 

They were in the process of commissioning two new 1000 keg per hour kegging lines when we visited. The fill 20, 30 and 50L kegs, with high gravity beer being cut to sales strength just before packaging. The beer gets 25 Pasteurisation Units (PUs). CO2 is 1.8-2.4 volumes and nitrogen 2.5-4. Which sounds quite a wide range to me but  you can't argue with hastily scribbled notes when you try and decipher them. 

After its initial hiccup Guinness Zero has been way more successful than anticipated. They are however extremely cagey about how they make it and we had one of the strangest experiences I've seen on a brewery tour talking to they guy in charge of it. We only got as far as the outside of the building in which it's made and most of our questions were nervously answered with "I can't tell you that". The smart money was on it being dealcoholised by reverse osmosis. The lack of alcohol means it gets 80 PUs. In Ireland you can get Guinness Zero on draught, an opportunity I did not take up as you can also get Guinness draught on draught. 

In the traditional Irish manner the lauter tuns are called kieves on the information display but they seem to have forgotten when making the banners. 

Whatever you call them though they're bleedin' huge. They make 7 million hl a year of beer at high gravity. Which I think it's fair to say is lots. There are three Steinecker brewing lines, the Guinness one making 1000hl at a time from 20 tonnnes of grist, 11 times a day. The ale and lager (Smithwicks, Harp, Hophouse, Carlsberg) goes at the same rate but with a brew length of 650hl. Due to demand some Guinness is also made on the ale and lager line. Lastly there's a roast malt barley extract stream. Given the awkward experience with the Guinness Zero guy I didn't ask about the Guinness Flavour Extract so the secret of the ooze will stay secret. 

They have four roller wet mills, Mash Conversion Vessels (MCVs), Lauter Tuns, Kettles and Whirlpools. The barley used is all Irish, Planet being the current malting variety with presumably feed barley for the raw and roast barley. The weak worts are recycled. The roast barley is unmilled and adds colour, flavour and aroma. The roast malt extract is combined with the Guinness stream in the kettle for a one hour boil. 

They mash in at 64.5°C rising to 72°C. There are two MCVs and one lauter tun for each stream. 

Fermentation takes two and a half days at 22°C with the ABV reaching 7.2%. The yeast is used for eight generations. They have 100 tanks ranging in size from 1200 to 4000hl. 

The roast house uses converted three tonne coffee roasters. They have bigger blades as barley grains are smaller than coffee beans. They are indirectly heated up to a maximum of 232°C (that's only for 90 seconds!). The last 20 minutes in a process taking two and a half hours are critical. The roasting chamber has water sprayed on at the end of the cycle to lower the temperature immediately. We were told 10% of the grain is roasted (though I'd heard 8% before) but my mind really got to boggling when I heard it's 20% in FES. It definitely has a darker head then draught Guinness. It will be as Guinness Flavour Extract that's added though. FES also has three hop additions. Probably extract there too mind. 

Sixty breweries worldwide produce Guinness under licence and samples from all of them are sent to Dublin for analysis. The lab has lot of shiny kit and sensory analysis also takes place by a 12 strong panel of trained tasters. They also deal with RTDs and the spirits Diageo makes for Africa. Local raw materials such as sorghum, millet and maize can be used and they have to be careful about Phenolic Off Flavours (particularly with sorghum) as the Guinness yeast is POF+. The limit for 4VG and 4VP is set at 0.25mg/l as that's the flavour threshold for most people. And they may allow a lot of diacetyl but they keep acetaldehyde low. 

pH and total acidity as acetic acid is measured. The haze meter uses 90° light at 650nmhey need to use a smaller cell for stout than lager though! 

Sorghum in particular is high in oxalic acid which can lead to beer stone problems. They measure calcium content, treat with nitric acid and measure again to show calcium oxalate. Not entirely sure how that works but give me the SOP and I'd have a go. 

The pilot plant was spread over four floors with of course the hammer and roller mills at the top. 

They have 10hl and 5hl breweries, which use 300 and 90kg respectively. 

They have a mash filter as well as a lauter tun. Wort's heated with an external calandria. 

The keg filler will go at 30 kegs/hr and they have a hybrid can and bottle filler. 

As Guinness supplies the UK from Dublin a lot of beer is tankered out: 60-65%! Forty 300hl tankers a day leave the site, most going to Runcorn, some to Belfast. They can fill a tanker in 45 minutes. 

That was the last brewery I went to on the Irish study tour and they really had left the best till last, it was fantastic. But did it make the best Irish stout? More on that later.