Brewing Chemistry: Music to your Taste

To get the best beer flavours ‘you don’t want too many lead singers’, explains Jaega Wise, head brewer at the up-and-coming London, UK, microbrewery Wild Card. Her metaphor reflects a unique perspective: while her day job exploits her chemical engineering training, she twilights as a session singer. So, if Wise wants a particular flavour to belt out like Beyoncé, she arranges other ingredients as backing. Tuning biochemical processes brings out the compounds responsible for the sensory high notes of each ingredient in turn.

When Wise ditched her previous job as a chemical trader in 2012, she and her fellow Wild Card founders liked the sound of making beer a career. Having built on their enthusiasm for ale and home brewing experience, today the company is becoming renowned for innovative drinks such as Unite Local Rhubarb Pale Ale. Flavoured almost entirely by rhubarb, it’s earned accolades even from people who don’t normally like beer.

Wild Card is also part of a recent surge in craft beer’s popularity, with many small producers now starring alongside international drinks giants. All of these brewers face the same chemical and biological challenges. But, the processes used at each end of the scale can reflect discordant outlooks.

On an anarchic Walthamstow industrial estate, inside the whitewashed brickwork and corrugated steel of Unit 8, is Wild Card’s brewery–bar. Here, Wise and her colleagues start the process of making beer by heating water to around 77˚C. They then transfer the water to a steel ‘mash tun’ tank and add malted barley, or malt. This creates the mash that, after filtering, becomes the wort that yeast feed on, fermenting sugars from the barley to become alcohol. Ensuring this process provides yeast with its ideal meal means getting the chemistry just right.

The chemical composition of the water used in the mash is vital, Wise explains. Burton in the UK, for example, spawned the ‘pale ale’ because the high level of sulfates in its local water releases more flavour from hops. The pH of the water matters too. The malting process involves roasting the barley, which produces compounds such as organic acids. Darker, maltier beers therefore need more alkaline water to neutralise the extra malt acidity. Lighter lagers need less alkaline water, like that in Pilsen (home of pilsner) in the Czech Republic.

London’s highly alkaline water therefore makes brewing lager ‘really challenging’, while making a dark, malty porter beer is ‘beyond easy’, Wise says. ‘A porter practically makes itself,’ she jokes. For India pale ale, she adds a mixture of calcium sulfate, sodium chloride and calcium chloride to the mash tun to ‘Burtonise’ the water.

The malt Wild Card uses – Maris otter – is one of its reliable backup singers. Malt contains starch carbohydrates and enzymes that break the starch down into small sugar molecules, which the yeast then feeds on. Water temperature is key to controlling which sugars form, and how much. Wise explains that Maris otter is a tasty, sturdy base, but not the fastest to break starches into sugars.

‘The choice of good malt is the brewers’ first critical decision,’ says University of Porto, Portugal, chemist Luis Guido. That’s partly because beer flavour changes as it ages and malt contains lipoxygenase enzymes that influence that process, he explains. Lipoxygenase degrades fats producing a ‘staling aldehyde’ called (E)-2-nonenal. The aldehyde brings what Guido calls ‘the unpleasant cardboard flavour of aged beers’. Guido and colleagues have found that lipoxygenase produces approximately 25% of the total (E)-2-nonenal found in the wort during barley roasting. His team consequently recommends tweaking the roasting process to minimise its formation.1

After adding the malt and hot water to the mash tun, the Wild Card brewers leave it for 80 minutes. They then ‘sparge’ the mash: adding hot water to destroy the malt enzymes and prevent them converting any further starch to sugars. The brewers can then filter off the malt, leaving just sweet wort liquid. ‘Then that goes into our kettle, which is boiled for 90 minutes,’ Wise says. ‘As soon as we see any boiling, we add our first hop.’…