How is alcohol free beer processed?
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 0.5% 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.
What does alcohol do during pregnancy?
According to research ‘Foetal Alcohol Syndrome’ is a series of mental and physical birth defects that can include mental retardation, growth deficiencies, central nervous system dysfunction, craniofacial abnormalities and behavioural maladjustments.
Alcohol is now recognized as the most common major destructive environmental agent to which a fetus is likely to be exposed. It is directly responsible for 10 to 20% of mental deficiency with IQ's in the 50 to 80 range, and one in six cases of cerebral palsy.
Luckily, they also say that FAS and FAE (Foetal Alcohol Effects) are 100% preventable when a pregnant woman abstains from alcohol. This, of course includes alcoholic wine.
Pregnancy and alcohol
Research from the Mayo Clinic, USA
Foetal Alcohol Syndrome
Foetal Alcohol Syndrome (FAS) is a condition that results from prenatal alcohol exposure. If you drink during pregnancy, you place your baby at risk of fetal alcohol syndrome.
The defects that are part of fetal alcohol syndrome are irreversible and can include serious physical, mental and behavioral problems, though they vary from one child to another.
As many as 40,000 babies are born with some type of alcohol-related damage each year in the United States.
Causes
When you drink alcohol, it enters your bloodstream and reaches your developing fetus by crossing the placenta. Because a fetus metabolizes alcohol more slowly than an adult does, your developing baby's blood alcohol concentrations are higher than those in your body. The presence of alcohol can impair optimal nutrition for your baby's developing tissues and organs and can damage brain cells.
The more you drink while pregnant, the greater the risk to your unborn baby. The risk is present at any time during pregnancy. However, impairment of facial features, the heart and other organs, bones, and the central nervous system may occur as a result of drinking alcohol during the first trimester, when these parts of the body are in key stages of development. In the early weeks of the first trimester, many women may not be aware that they're pregnant. Alcohol may affect the brain of the fetus at any time during pregnancy.
Prevention
Doctors haven't identified a safe level of alcohol that a pregnant woman can consume. But, experts do know that FAS is completely preventable if women don't consume alcohol during pregnancy.
These guidelines can help prevent fetal alcohol syndrome:
- Stop drinking alcohol altogether if you're planning to become pregnant, as soon as you know you're pregnant or if you even think you might be pregnant.
- Your baby's brain, heart and blood vessels begin to develop in the early weeks of pregnancy.
- Continue to avoid alcohol throughout your pregnancy. Fetal alcohol syndrome is completely preventable in children whose mothers don't drink during pregnancy.
- Consider giving up alcohol during your childbearing years if you're sexually active and you're having unprotected sex. Many pregnancies are unplanned.
