OnTap Magazine

Filling the coolship with freshly boiled wort Coolship at De Dolle Brouwers in Esen, Belgium the natural micro ora and wild yeast from the surrounding area inoculate the wort. When the wort is cooled, it is transferred to a mixing tank for the micro ora and wild yeasts that accumulated on the wort surface to blend with the rest of the wort before being transferred to wooden barrels. SOUTH AFRICA’S COOLSHIP At Hey Joe Brewing Co., we have a 50hl stainless steel coolship – the only known commercial coolship in South Africa. We rst utilised the coolship in October 2018 although it was rather by accident that we ended up using it during our commissioning brew. Our centrifuge was not yet functioning and our brewhouse is not equipped with a whirlpool, so we had to use the coolship as a settling tank for hops and trub. We transferred the hot wort into the coolship and cooled it to 80°C, added more hops and crushed coriander seeds before cooling the wort further to 20°C to pitch the yeast. e wort was then fermented in a closed vessel. Our coolship room has two rows of windows which open to the natural air and surrounding fynbos mountains. is biome ensures a vast collection of micro ora to inoculate into our lambic style beers. Sadly we have not yet released a coolship beer as we rst need to set up a temperature-controlled barrel room in order to age the brew to perfection. ere is a lot more to lambic brewing than simply using a coolship though. In fact, everything from mashing to hop additions di ers from the way you might be used to brewing. Typical mashing regimes aim to gently extract sugars from the malt to supply a simple source of food for yeast to feast on during fermentation. In lambic brewing the goal is to vigorously extract sugar from malt by means of a “turbid mash”. is way, substances like tannins, starches and polyphenols are extracted from the mash. is will give the wild yeasts something to chew on during the long journey in the oak, ensuring complexity in the nal beer. In modern brewing, the fresher the hops the better. But here aged hops are used – ideally whole leaf hops. e method behind the madness is that in traditional lambic- style beers you want zero bitterness. e bitterness in beer originates from the alpha acids in hops. ese disintegrate from the cones as hops age. When hops start to smell like old cheese, you know you have a perfect hop for a coolship brew! Be sure to boil for at least 3½ hours to boil o the unpleasant cheesy avour. However, even though the hops have lost their bittering factor they still retain their antibacterial properties, acting as a natural preservative. Using hops like Styrian Goldings, with a low alpha acid content and a higher tannin content, is a good choice for a lambic-style beer. ey say “nothing in life is free” but when brewing spontaneously fermented beer, you do get one free ingredient – wild yeast. Now you as the brewer just need to ensure the perfect home for the wild yeast to manifest itself for a few years. You never physically need to add yeast or bacteria. e micro ora from the air that wafts into the brewery will contain su cient wild yeasts to get your brew fermenting and maturing over its time in the oak. A COMPLEX FERMENTATION e rst important note for the perfect “wild wort” is the weather. Coolship beer should only be brewed in winter when your region’s climate area reaches as close to 0°C as possible. Warmer temperatures would introduce unwanted micro ora that would spoil the nal beer. e wort pH is another important aspect of ensuring that you capture the wanted micro ora. Aim for a wort pH of 4.7 or lower when transferring to the coolship. Use lactic acid to reduce the pH to the coolship before transferring the wort. e lambic fermentation kicks o after 3-7 days with the non-maltose fermenting yeast and enterobacteria. is phase lasts about 30-40 days during which monosaccharides become depleted and the initial acidi cation starts to commence due to the aid of certain pediococci microbes. In the second phase when alcoholic fermentation kicks in and Saccharomyces species including increase as well as rapidly multiplying lactic acid bacteria (LAB). e acidic environment created by the initial fermentation now has created a less ideal environment for enterobacteria as well as the ethanol produced. After about six months, the Saccharomyces species are no longer active and are replaced by the activity of Brettanomyces . At 12 months, the “Brett” is the prominent specie followed by LAB to start thriving followed by acetic acid bacteria, which further increases the acidity. It is clear that brewing with a coolship and speci cally producing lambic style beer is far from a walk in the park and takes careful control in the initial brewing phases. ereafter it is up to the wild microbes to do their thing. So much of brewing involves a strict adherence to science, but sometimes it’s fun to throw out the rulebook and brew just as it was being done hundreds of years ago. TECH TALK 34 | Spring 2020 | ontapmag.co.za