Distil the chemical processes used to keep beer’s flavour, smell, colour and stability
Whether it’s mocktails, alcohol-free beer or low-alcohol wines and spirits, there’s no question that keeping people hangover-free is big business.
In the UK, the no- and low-alcohol beer market was worth more than £350 million in 2021, and in China it’s a multibillion-pound industry. And although there’s no such thing as truly no-alcohol beer – alcohol-free labelled beers can contain up to 0.5% alcohol by volume (ABV) – removing most of the booze is down to some basic chemistry.
An alcohol molecule has at least one hydroxyl (–OH) functional group bound to a carbon atom. This means even something as complicated as cholesterol is still, technically, an alcohol. But, the drinks’ labels don’t describe the chemical definition – instead, they mean ethanol (CH3CH2OH).
Ethanol isn’t just for drinking: it makes a terrific fuel and is an important industrial precursor to make other molecules too. It has a lot of different effects on the body – far too many to go into here – but the important part comes when you consume more than your liver can metabolise, and it interferes with neurotransmission in the brain. The result is that you get drunk. However, low-alcohol beer has so little alcohol that your body can usually deal with it easily, keeping you hangover-free.
Brewed for flavour
Brewers follow the same process used for thousands of years to make beer. First, they mash malted barley in hot water. Then, they extract sugars in a liquid known as wort, boil it with hops and ferment the liquid. The fermentation process involves yeast — a fungus that feeds on the sugars to produce ethanol, carbon dioxide and by-products that add flavour.
No yeast, no fungus creating ethanol, no flavour
There are multiple tactics a brewer can employ to ban the booze. One is to sidestep the fermentation process altogether by not adding yeast to the wort: no yeast, no fungus creating ethanol, but also no flavour. Unless you use additives to spice up the flavour, you get a rubbish-tasting beer. Another option is equally simple: just dilute your beer. By adding water, you reduce the ABV, but also make weak beer.
This leaves the modern process of dealcoholisation: removing the alcohol after fermentation. Again, there are a range of techniques that brewers can use, but most involve either heat or a membrane-based process.
One common approach is vacuum distillation. This involves heating the beer at low pressure, which means the ethanol and water in the beer evaporate at different temperatures and separate. Brewers take the ethanol out, and reblend the remaining liquid, this time with a little carbonic acid. The downside is that they lose various flavour molecules with the alcohol. Brewers must separate the liquid once more, then reintroduce the flavours into the now (nearly) alcohol-free beer. A variation on the technique is stripping, in which water vapour or a non-reactive gas (such as nitrogen) is passed through the wort under vacuum to carry away the ethanol. You can decaffeinate coffee beans using a similar technique.
Another alternative is reverse osmosis. Rather than low pressure, the brewer uses high pressure to force the beer through a semipermeable membrane. This membrane allows water and ethanol through but leaves larger molecules (such as those that give beer its taste) behind as a concentrate. Brewers can then dilute the concentrate with fresh water to make the booze. The downside is that, although most of the flavourful stuff is in the concentrate, they lose some smaller molecules or those dissolved in the beer’s gases. Without care and attention, the beer loses its flavour, smell, colour and even stability – meaning that your alcohol-free beer isn’t as good as the real thing.
Why not watch, and share, this TikTok over a brew?
@royalsocietyofchemistry Party season has always meant lots of drinking but a new wave of drinks are cutting out the hangovers using #chemistry #learnontiktok #christmas ♬ vlog, chill out, calm daily life(1370843) - SUNNY HOOD STUDIO
Watch, and share, this TikTok (bit.ly/47KgGCn) over a brew