Tastings School - How low can you go?

Tastings School

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How low can you go?

Daniel Cooper tackles the subject of low and no alcohol beer, and how they are made.

We have all been there. It’s your turn to be the designated driver, but now you’re at the bar you really want a beer. So what do you do, go for the soft drink option or order a low alcohol beer? Let’s face it not many of us would actually order a low alcohol beer would we?

A quick glance at the sales figures would suggest that perhaps most of us would choose soft drinks over low alcohol beer. For example in the United Kingdom low alcohol beer grew to occupy 1.1 per cent of beer sales in 1989. But this had declined to just 0.3 per cent of sales six years later.

But with increasingly stringent drink driving laws, greater awareness of the health issues associated with alcohol consumption and the negative media attention associated with binge drinking, perhaps there is a growing demand for products that are low in alcohol but still have the great taste of beer.

First introduced in prohibition America the definition of a non or low alcohol beer varies from country to country and can be a little confusing. For example in the UK there are essentially three categories, reduced alcohol beer containing between 1.6-2.5% alcohol by volume. Low alcohol beer where the beer contains less than 1.2% ABV and alcohol free beers which must have no more than 0.05% ABV.

However, in the United States a beer-like beverage which contains less than 0.5% ABV can legally be called non-alcoholic but cannot be described as beer.

All very confusing, therefore for ease of definition in this article low alcohol beers can be defined as containing an alcohol content of less than 2.5% ABV and alcohol free as 0.05% ABV.

So how are low, and alcohol free beers brewed?

Essentially there are two main ways of brewing a beer with low levels of alcohol. You can limit fermentation so that the yeast is unable to produce alcohol or you can remove the alcohol from a normally brewed beer.

The earliest low alcohol beers were all brewed using the first method of limited fermentation. The aim of limited fermentation is to allow the yeast to produce the flavour compounds that we would typically associate with a beer but only produce low concentrations of alcohol. This of course is very difficult to achieve and in practice tends to lead to beers which are overly sweet. However, there are a number of ways by which a brewer can limit fermentation and therefore brew a low alcohol beer without having to invest in specialised equipment so the method does have its attractions.

A very common limited fermentation technique utilised by brewers is to allow a normal fermentation to occur until a certain alcohol concentration is reached, for example 2.5% ABV. The brewer will then stop the fermentation by removing the yeast. This is often achieved by rapid cooling of the fermenting beer to a temperature of 0ºC. The sudden drop in temperature causes yeast to sediment out of the beer and fermentation is halted resulting in a partially fermented low alcohol beer.

Brewers have also found that it is possible to limit fermentation by controlling the sugars in wort that are available for yeast to ferment. If you bear in mind that brewers yeast can only ferment simple sugars such as glucose, fructose, sucrose and maltose it is possible, by manipulating the mashing conditions, to limit the production of these simple sugars and therefore reduce the ability of yeast to ferment.

Thus by mashing in at a higher than normal temperature, say 75ºC to 80ºC, the enzymes present in malt that would normally convert starch into simple fermentable sugars are rapidly inactivated and so do not work. The modified wort produced from this elevated temperature mashing contains only low levels of the simple sugars that yeast like and therefore only allows a limited fermentation to occur.

The problem with limited fermentation methods is that because fermentation is not allowed to proceed to completion the flavours that would normally develop during this stage of the brewing process are reduced and some of the undesirable flavours from malt are not removed. Thus some argue that low alcohol beers brewed using these methods don’t quite possess the flavour characteristics that consumers would expect from a beer.

Many brewers have therefore experimented with methods of removing alcohol from a normally fermented beer. The argument is that because the beer has been brewed in the traditional way the flavour will be more rounded and typical of beer.

There are a number of methods that can be employed to remove alcohol from beer and these include distillation, evaporation, reverse osmosis and dialysis.

Distillation relies on the fact that alcohol has a lower boiling point than water. Therefore when beer is heated the alcohol is distilled off and leaves behind de-alcoholised beer.

Unfortunately it is not as simple as that.

Many of the flavour compounds in beer have low boiling points as well so will be lost along with the alcohol. This requires some flavour adjustment to take place after distillation has occurred.

The distillation of beer can be carried out at either ambient pressure or under vacuum.

Unfortunately the prolonged heating involved in ambient pressure distillation can have a negative impact on beer flavour. Fortunately if you carry out the distillation under vacuum lower temperatures can be employed. This is because, as anybody who has made a cup of tea up a mountain or, for those of us who prefer a more sedate life, used a pressure cooker will know if you vary the pressure water will boil at different temperatures.

For example water will boil at a lower temperature in the low pressure environment that you would encounter up a mountain but will boil at a much higher temperature when stuck in a high pressure cooker. Therefore vacuum distillation enables a lower distillation temperature to be employed to remove the alcohol from beer and so is preferred.

Evaporation is another method utilised to remove alcohol from beer but again there is a possibility of the elevated temperatures employed damaging the flavour of the finished beer. Therefore the methods of reverse osmosis and dialysis, which do not rely on heating the beer, are generally preferred.

Reverse osmosis relies on the fact that alcohol is quite a small molecule. Therefore when normally brewed beer is filtered, under high pressure, through a semi-permeable membrane alcohol can be removed with very little loss of flavour from beer. In practice the technique does result in the loss of water and some small molecular weight flavour compounds and so some adjustments have to be made to the beer after the treatment.

Dialysis due to the gentle treatment of the beer being de-alcoholised is perhaps the most satisfactory method of removing alcohol from beer. The technique works by allowing beer to flow across a membrane on the other side of which, flowing in the opposite direction to the beer, is the dialysate which is typically pure deoxygenated water with perhaps a small percentage of the beer being de-alcoholised.

The difference in concentration of the alcohol in the beer and the dialysate means that the alcohol diffuses across the membrane from the beer into the dialysate. Some small molecular weight flavour compounds are lost during the process but these can be adjusted for in the final low alcohol beer.

While there are some successful low and no alcohol beers, which manage to attain an excellent match in terms of flavour to their normally brewed counterparts, the idea of beer without alcohol remains a contradiction in terms for many consumers. It remains to be seen if this contradiction will continue to be a hurdle to the growth of low alcohol beers.