OnTap Magazine

ontapmag.co.za | Autumn 2025 | 43 W e in South Africa are no newcomers to sour beer; Umqombothi, a traditional beer made of maize, sorghum and maize malt, yeast, and water, is deeply rooted in South African culture. The Xhosa word even translates to “African beer”. Yet, when it comes to the production and availability of commercial sour beers, we fall well short of Europe and the United States. Not only are these beers readily available in the United States, but they are also revered; in 2023, sours were the fourth most popular craft beer style. The origin of sour beers in Europe is much older and more localised due to a well-established traditional beer culture based on region-specific styles. No place is more iconic in this regard than the Senne Valley, southwest of Brussels, where the ‘wild side’ triumphs in the spontaneously fermented sour ‘Lambic’ beers. Despite our own historical and regional tradition of sour beer, the South African craft beer industry is still young and as a result, some of these more ancient beer styles are still finding their way into South African craft beer. The ingredients and processes required are also expensive, which gives such beers a higher price point. Oak Barrels used for ageing and fermentation are not easy to come by and fruit such as Raspberries and Cherries are expensive, particularly out of season. A 220L fruited Lambic barrel typically will need 50kg of fruit added to achieve the desired result and character of a fruited beer. There are three main methods of producing sour beers, which vary in process and product complexity. A firm favourite of many brewers due to its simplicity, control and lower risk of bacterial cross-contamination. It involves adding Lactobacillus bacteria to the wort in the kettle, which subsequently pro- duces lactic acid, yielding a mellow and tangy flavour at low levels, which can be sharper at higher concentrations. It’s sim- ilar in taste to the acid found in yoghurt, buttermilk, and other dairy products. Ket- tle souring can take anywhere from 24 to 72 hours and is followed by boiling to kill off any bacteria present. This ensures that downstream equipment such as fermen- ters and transfer lines remain uncontam- inated. The sour wort is then fermented using any traditional yeast of choice, al- lowing for a range of expression in the final beer as any beer style can be soured using this technique. This involves using more than one yeast or bacteria for fermentation. A good example of commercially available mixed fermentation sour beers comes from Rodenbach, a brewery known for its barrel-aged sour beers located in Roeselare, Belgium. Isolated yeasts and/or bacteria can be grown by ‘yeast banks’. A local example of this is Liquid Culture, an initiative by the University of the Free State intended to promote yeast culture for the South African craft beer sector. Yeast banking involves storing yeast strains long-term so they can be reused and preserved as part of a collection. KETTLE SOURING: MIXED FERMENTATION: