A visit to Midleton Distillery

Since I've been a member of the Institute of Brewing and Distilling the importance of distilleries to seems to have been growing. There is a lot of money in spirits which I'm sure is entirely coincidental. Whisk(e)y distilleries are great places to visit though, usually old buildings, gleaming copper and dusty oak barrels. 

Which is also all that you're usually allowed to photograph and they tend to get twitchy about electric devices in alcohol rich atmospheres. 

Copper has to be used in stills to get rid of unwanted sulphur flavours and  wood is required for flavour and colour development. 

The Midleton distillery is big, Jamieson whiskey being one of the brands made there. Current output is 68-69 million litres of alcohol per year, grain whiskey making up 48 mla and pot whiskey 20.5 mla. Not being a distiller myself it's not obvious to me how big that is so lets see what I can convert it to in language I understand: 

My notes are a little confusing on the whiskey washes, as I have them down at 12-15% ABV and 10-12%. I'll take 13.5% as the average and 68.5 million litres of alcohol would take just over five million hectolitres of whiskey wash to make. So in brewery terms we're talking large multinational size. There are 500 people on site so that fits in too.

100,000 tonnes of maize, 35,000 tonnes of barley and 20,000 tonnes of malt are used annually. I'm not really up on Irish Whiskey regulations but using unmalted barley is distinctively Irish, as is triple distillation in pot stills (double distillation being preferred in Scotland).

We did get a good look at the six pot stills but sadly not the continuous still, a much more complicated bit of kit where the grain whiskey is made. Continuous stills give a purer spirit too: 94.4% ABV in this case, whereas the pot stills' new make spirit comes out at 84.5% ABV after the third distillation (first the wash still, then the feints still, then the spirit still). The wash is pre-heated from 25°C to 50-60°C on its way to the stills, which have a capacity of 385hl. Production of low wines at 45-50% ABV takes six to seven hours with the cut giving a short head and long tails. From the second still they get a 70% ABV product (high wines?). The stills have straight necks with lyne arms at 90°. There are horizontal condensers. The spirit is cut to 63.4% ABV for maturation. The stills are cleaned using 3% caustic.

For the pot whiskey the wash is made from 60% barley and 40% malt using mash filters. The grains are hammer milled before going to a mashing in vessel then into Mash Conversion Vessels followed by mash filters (they have three mash filters and MCVs). Enzymes are added to the mash, something they don't allow in Scotland. The mash starts at 52°C, has an hour at 60­°C and is raised to 77°C before going to the mash filter. The mash filters take at least 2.5 hours to separate the wort, 300hl of strong worts (75°S if all goes well) going to Fermenting Vessels (or should that be wash backs?) and 60hl of weak worts are recycled into the next mash. Eight tonnes of grist are used and usually there are 26 brews in 24 hours, though they can do 30 at a push. FVs are 2,000hl. Fermentation is carried out using M yeast supplied as a cream to 10-12% ABV (so I guess the higher figure I had is for the grain whiskey washes). 

They fill 3,000 barrels a day, mostly 200L. The barrels are filled from the top  through a hole drilled in the head. Evaporation and filling/emptying losses work out at 2% a year plus 4%. The barrels get three uses. Before packaging the whiskey goes through a vibrating sieve to remove char and wood before going through 150 and 110μm filters.  

We had time for a quick taste and they were kind enough to give us a sample to take away too.

It managed to make it back home before being guzzled. Aged in port casks and sweet it was ideal for a whisk(e)y lightweight like myself.