Beer : Health and Nutrition

The Basics of Malting and Brewing 79
taken, is severely detrimental to quality because it oxidises components of beer, leading
to staling and the formation of haze (Bamforth et al. 1993).
The most oxidisable molecules in beer are the polyphenols (Owades & Jakovac 1966).
On the one hand this serves to protect beer against staling, as these substances act as
oxygen scavengers (Walters 1997). However, following their oxidation, they polymerise
and crosslink with proteins (the tanning reaction) to form insoluble complexes, which
afford an unsightly turbidity (McMurrough & Delcour 1994). Generally speaking, the
brewer will err on the side of caution and seek to remove polyphenols as much as possible,
by adsorbing them on to polyvinylpolypyrrolidone (PVPP) after the lter process.
This will take the total polyphenol content down to less than 100 mg/L, which means
that this class of compounds is somewhat less in beer than in products such as red wine
and cider, where they contribute to astringency. The PVPP does not enter the beer.
Nitrogen has been added to beer for many years, mostly in Ireland and the UK, to
promote foam stability (Lindsay et al. 1996). As little as 20 mg of N 2 per litre is suf cient
to enhance beer foam quality, levels which are vastly lower than those of CO 2 . In small
pack beer the nitrogen is usually accompanied by the use of widgets, which promote
nucleation. These plastic or metal inserts are perfectly safe, provided they do not display
any disintegration in the container. As the atmosphere is some 79% nitrogen it hardly
seems that we need worry about the quantities deliberately introduced into beer.
Water
As already stated, most beers comprise 90–95% water and so its composition is critical
as a determinant of beer quality. Brewing demands much more water (5–20 times) than
the amount which ends up in the beer (UNEP 1996). A lot is needed for cleaning and
for raising the steam needed for heating vessels.
The water must contain no taints or hazardous components and a brewer may treat
all water coming into the brewery by procedures such as charcoal ltration and ultraltration
(Katayama et al. 1987). The water must also have the correct balance of ions
(Taylor 1990). Traditionally ale brewing was established in towns such as Burton-on-
Trent in England. The level of calcium in the water of the region is relatively high (about
350 mg/L), and it is claimed that this is good for ales, whereas low levels of calcium,
such as the less than 10 mg/L in Pilsen, is best for bottom-fermented lagers. In many
places in the world the salt composition of the water is adjusted to match that rst used
by the monks in Burton in the year 1295, a process known as ‘Burtonisation’. Often
the brewer will simply add the appropriate blend of salts to achieve this speci cation.
To match a Pilsen-type water it is usually necessary to remove existing dissolved ions
by deionisation, perhaps by a ltration technique.