Beer : Health and Nutrition

The Basics of Malting and Brewing 71
There are many de nitions worldwide about what constitutes low-alcohol products.
Perhaps the most stringent is in UK, where non- and low-alcohol beers (NAB/LABs)
contain less than 0.05% or 1.2% ABV, respectively. They are produced either by removing
the alcohol from a full-strength brew (by techniques such as vacuum distillation or
reverse osmosis), or by restricting the ability of yeast to ferment wort (either by making
a wort containing very low levels of fermentable sugars or by ensuring that the contact
between yeast and wort is at a very low temperature and for a relatively brief time).
The chemistry of beer
Ethanol
As we shall see in Chapter 6, there is increasingly good evidence for the bene cial impact
of moderate levels of ethanol on the body. There are several other effects of alcohol on
the quality of beer. It contributes directly to avour, by impacting characters variously
described as warming and sweet as well, of course, as alcoholic. It also moderates the
contribution of other components to avour by in uencing their partitioning between
the body of the beer and its headspace (‘the nose’). Ethanol also in uences the foaming
properties of beer (Brierley et al. 1996). It lowers surface tension, and so aids bubble
formation, but it also competes with other surface-active molecules (notably proteins)
for places in the bubble wall, thus detracting from stability of the head.
Beer strength is usually de ned in terms of alcohol by volume (ABV), i.e. the number
of cm 3 of ethanol per 100 cm 3 of beer. Sometimes alcoholic strength is described in
terms of weight per volume. As the speci c gravity of ethanol is 0.79, this means that
a beer that contains 5% alcohol by volume has approximately 4% alcohol by weight.
One of the most relevant examples to use by way of illustration is the so-called ‘3–2
beer’ in Utah. Most of the beer in that US state is in this category, which refers to the
fact that it contains no more than 3.2% by weight. This is of course 4% when quoted
on the basis of volume.
Another way of describing the strength of a beer is on the basis of its ‘original
gravity’ (known as ‘original extract’ in the US). This is variously quoted on the basis
of speci c gravity or, increasingly commonly, degrees Plato. It is basically a measure
of the strength (approximating to the sugar content) of the wort prior to fermentation.
During fermentation, the fermentable sugars are converted into alcohol, leaving behind
that proportion of the solubilised starch that is not fermentable. Sugar solutions have a
high speci c gravity (weight per unit volume), as compared to water (1 mL of which
weighs 1 g – i.e. the speci c gravity is 1.00) and to ethanol (speci c gravity 0.79). Thus
there is a fall in speci c gravity during fermentation and the nal speci c gravity of a
beer re ects the balance between ethanol and the residual unfermentable ‘dextrins’ (see