Inside The Factory - Series 8

Episode
Episode 5 - Stout
Broadcast Info
2024 (59 mins)
Description
Gregg Wallace explores the secrets of the Guinness brewery in Dublin to reveal how it makes two million litres of Irish stout every single day. Gregg starts at the intake bay with a delivery of thirty tonnes of malted barley, which has been steeped in germination tanks to encourage it to grow. As the grain sprouts, it starts to convert its proteins and carbohydrates into sugar rich starch which is essential for the brewing process. Sixteen tonnes of malted barley is sent into the brew house where it passes through a mill which grinds it down to a fine powder called grist. Then, along with 72,000 litres of water, it’s pumped into a huge brewing vessel, where Gregg meets Eamonn Power who shows him the process. Inside the huge tank the malted barley and water, now called mash, is heated to around sixty degrees Celcius. The combination of water and heat causes the starch inside the ground malted barley to swell and rupture, releasing long chains of sugar molecules. Enzymes also contained within the malted barley then attach to the long sugar chains breaking them down into shorter chains which ferment more easily into alcohol. After two hours, the sweet-smelling sugary liquid called wort is separated from the grain. Gregg then learns how the liquid is boiled to kill any bacteria before hops are added. There is another vital ingredient required to make stout - roasted barley - so Gregg heads to the roast house. There he learns how pure barley is roasted in an oven at 232 degrees Celcius, which gives it an intense roasted flavour. Then it’s sent back to the brew house, where it’s turned into wort and blended with the malted barley wort. Of course, stout isn’t stout without alcohol, so Gregg heads to the brewery’s microbiology lab to meet Dan Kerruish who introduces him to the specialist strains of yeast that will convert the sweet wort into stout. Gregg learns how the some of the strains of yeast date back to 1903 and how they are grown in the lab so that they have enough to turn huge tanks of wort into alcohol. He then wheels his tank of yeast across the huge site to the fermentation plant and hooks it up to a fermentation vessel where it joins up with thousands upon thousands of litres of the sugary wort. While standing on top of one of the factory’s 52 colossal 28-metre-high containers Gregg learns how over two and a half days, the yeast feeds upon the sugars, expelling alcohol and carbon dioxide. The yeast is re-used to help ferment other vessels and the carbon dioxide is extracted. They’re left with 7.2% alcohol volume stout. This is too strong for the Irish market, so it’s blended with water bringing down the alcohol content to a more palatable 4.2%. Over in the kegging department, Gregg meets packing manager, Patricia Gormley who shows him how they add nitrogen gas to give the stout its famous creamy head. With the stout finished, it’s piped into metal kegs under high pressure. Finally, Gregg helps to make a delivery of beer to the local pubs. Elsewhere in the episode, Cherry Healey visits a water treatment centre to learn how reservoir water is treated to provide clean drinking water to the people of Dublin, as well as to the stout brewery. And she visits a farm in Worcestershire to help with the hop harvest. Historian, Ruth Goodman delves into the history of Irish pubs, and explores the extraordinary story of how pub games helped the Allies in the Second World War.
Genre
Nutrition; Science; Technology

How to cite this record

The Open University, "Inside The Factory - Series 8". https://learningonscreen.ac.uk/ou/search/index.php/prog/248064 (Accessed 10 Jan 2025)