There has been a recent trend in the last few years to embrace non-alcoholic beer (beer with 0.5% or less ABV). How does this beer work? Do you just put in all the ingredients except the alcohol? So, beer minus yeast? Well no because yeast is a major contributor of beer flavour, without which it’s not going to taste like beer. This method (fermentation-free brewing) is used in some Islamic countries such as Iran. It’s as cheap as making usual beer and the process is straight forward. Unsurprisingly this technique will never take off in our markets. The resulting “beer”, even with extra additives, tastes pretty dull, flat, and bland.

Flavour is in fact the main challenge in the production of non-alcoholic beer. Trying to get the flavour as close as possible to alcoholic beer has proven tricky economically. To date, all the commercially viable methods can be grouped into three categories:

Dilution;
Restricted alcohol fermentation; and
Alcohol removal/dealcoholisation.

Dilution method: water down the beer. I kid you not. The beer is made with extra hops and more grain than usual. Yeast is added, and naturally despite the extra sugar from the grain, still only produces alcohol to its kill switch ABV tolerance e.g. say 8% ABV. Yeast, now in a toxic environment it can’t handle, then quits fermenting. The beer is then watered down with either water, carbonated water, or dealcoholized beer, then carbonated and packed. The production method is cheap and tastes it too.

Restricted Alcohol Fermentation: simply make beer with less alcohol. Not rocket science just not going off like a frog in a sock. There are strains of yeast that have an ABV% tolerance of 0.5%, meaning they produce alcohol up to 0.5% ABV at which point they consider their environment too toxic to continue to produce alcohol. By using these yeasts you can make 0.5% beer in the usual way and avoid the flavour loss associated with dealcoholising methods. The issue with this restricted alcohol fermentation method is the lack of yeast varieties. The reason for the wide and extensive commercial variety of yeast strains is, in addition to different ABV% tolerances, different strains produce a wide variety of flavour profiles. Different beer styles need different flavour profiles. The number of low ABV% tolerant yeast are limited, and so therefore are the variety of beers that can be made by them and still resemble the finished taste of their more alcoholic counterparts.

Alcohol removal/ dealcoholisation: beer is made in the usual way and then the alcohol is removed. Here’s some ways the alcohol can be removed:

Distillation This method works because the boiling point of alcohol is lower than the boiling point of water. As you heat up the beer the alcohol will boil off before the water does. Think about adding red wine to a steak sauce. The sauce gets this amazing flavour from the wine but it’s not alcoholic. That’s because right at the start of the reduction of the sauce the alcohol has already boiled away, but flavour stays. Same with distilling beer. Trouble is though, not all flavour remains and what’s left can be altered. Beer flavour volatiles are extracted during the distillation along with the ethanol.

Ethanol is a needy bugger and latches onto to whatever it can bind with. This is why methylated spirits is such a great cleaner. Methylated spirits is ethanol with small percentage of methanol mixed in to make it poisonous so we don’t drink cheap alcohol. It’s cleaning properties work by the ethanol molecule wanting to bind to whatever it can, like grease, water, and dirt. When ethanol is bubbling up through the beer solution and escaping surface tension it picks up other molecules. The flavours they carry with them are called flavour volatiles because they are compounds that have a high vapor pressure and low water solubility, that is they easier release into the air. Depending on how high you allow the ethanol vapour to rise before you collect it depends on how much flavour volatiles you collect in addition. The heavier flavour volatiles drop out of the vapor stream before the lighter ones. This is why the height of a pot still is so important in creating the flavour profile of a rum and whisky. In the process of whisky and rum though it’s the evaporated alcohol and flavour volatiles we keep. In the process of dealcoholising beer distillation, the evaporative is discarded and it’s the solution left at the bottom of the still, the wash, that we keep. Because we lose flavour in the evaporative, and we effectively “cook” other flavours left in the wash, the resulting dealcoholized beer doesn’t taste like it should. The beer, and all its delicate flavours post fermentation are negatively impacted by the heat required to distil. At one atmosphere (14.7 PSI) the boiling points of applicable alcohols are as follows:

Vacuum Distillation This method tries to avoid the unwanted effect heat has on changing the beer flavour. Unfortunately like distillation, this process still does loss volatile flavours. By reducing the pressure, the boiling points of the alcohols are lowered. A typical reduction in pressure is to around a fifth of an atmosphere is sufficient (200 mbar = 2.9 PSI). Research has shown lowering further than this is doesn’t increase efficiency and so isn’t worthwhile. Under pressure of 40 to 200 mbar the beer only needs to be heated in the range of 30 to 60°C. These lower temperatures avoid the “cooking” of flavours, but as stated doesn’t avoid flavour volatile loss, which still results in beer not tasting right.
Water Vapor/Gas Stripping Under Vacuum This is another application of vacuum but without the distillation. This method bubbles neutral gas (nitrogen or carbon dioxide) or water vapor through the beer under vacuum to carry away the alcohol. The beer is at a pressure one bar (14.5 PSI) lower than outside pressure. This method is successful in retaining flavours unaltered.
Dialysis This method filters the beer and then distils off the alcohol. First the beer is filtered through a semi-permeable membrane which strips out all the larger molecules. Then the beer is stripped of its alcohol in the still under vacuum. With the larger molecules stripped out before distillation flavours are lost and the result is a plain tasting beer lacking luster.

Reverse Osmosis This method filters the beer under high pressure. The beer is squeezed through a semi-permeable membrane at a high pressure above natural osmosis. It filters out water, alcohol and other small molecules. The larger flavour molecules are left in the beer. Water is added back. The result is a beer which is compromised in flavour, fragrance, colour, acidity, and stability. This method is really not a winner.

For those wondering, osmosis is the spontaneous movement of a molecules from a high concentration to a low concentration through a semi-permeable membrane, a surface/barrier that lets somethings through but not others. The molecules move so that the two separated solutions tend towards equal concentration. To achieve reverse osmosis you get molecules to move from a lower concentration to a higher one. This is done via hydrostatic pressure (pressure of the solution due to the force of gravity) which pushes the solution through the membrane.

Above is a general diagram of reverse osmosis. When used in beer, both the water and alcohol molecules are small and so pass through the membrane. Source: Sciencenotes.org - What is Reverse Osmosis?

Osmotic Distillation Place a microporous membrane between the beer and water. Molecules small enough from the beer pass through the membrane and into the stripping water. The “holes” or pores in the barrier are made large enough for ethanol molecules to pass through. Unfortunately holes large enough for ethanol are also large enough for small flavour volatiles too. This method is good because it doesn’t strip water out of the beer as evaporation and reverse osmosis does, but it regrettably losses flavour, phenolics, ions, and dissolved gases such as carbon dioxide and sulphur dioxide. Interestingly, though in a bad way, not all gas exchange through the membrane is a loss to beer. This method also has the disadvantage of introducing oxygen gas into the beer. As the dissolved oxygen in the stripping water is generally higher in concentration than that in the beer the oxygen, molecules travel the “wrong way” down the “one way” street, going from the stripping water and into the beer. Dissolved oxygen in final beer is a bad guy. It contributes to oxidisation, “aging”, so effectively threatens shelf life.

Absorptive Alcohol Removal Spend time and money adding chemicals to the beer to absorb the alcohol. This method applies chemicals that bind to the alcohol, which is later surrenders the alcohol via various processes. This chemical method doesn’t scale up well commercially and so hasn’t taken off.

Of all of these methods of producing non-alcoholic beer, the most commercially adopted have been reverse osmosis and dialysis. The advantage of using semi-permeable membrane to filter out the alcohol avoids the high “cooking” temperatures of distillation. Commercially these mild-operation temperatures also lead to low-energy consumption while maintaining high yield of non-alcoholic beer from the original beer wash. The most successful of all the methods, in terms of flavour retention, is Water Vapor/Gas Stripping Under Vacuum.

Non-Alcoholic Beer - How is it Made?