Beer : Health and Nutrition

The Basics of Malting and Brewing 69
at –1°C for a minimum of three days, under which conditions more proteins drop
out of solution, making the beer less likely to go cloudy in the package or glass. The
long-term stability of beer may also be aided by the use of materials downstream that
remove haze-forming protein or polyphenol. For the latter, the one choice is polyvinylpolypyrrolidone.
Protein may be removed in three ways: by adsorption on silica gels
that are made from sand, by precipitation with tannic acid derived from gallnuts, or
by hydrolysis with the enzyme papain from the pawpaw. This is the same enzyme that
comprises meat tenderiser.
The ltered beer is adjusted to the required carbonation before packaging into cans,
kegs or glass or plastic bottles. The packaging operations are rigorously designed to
ensure that the product is delivered in secure (tamper-proof or at the very least tamperevident)
packages that minimise the opportunity for air ingress (oxygen promotes
staling). Modern packaging lines incorporate highly ef cient systems to ensure that
packages will not contain foreign bodies and furthermore that such items cannot be
introduced during the packaging process itself.
Countries such as the UK have regulations which stipulate that packaging materials
may not react with or alter the organoleptic properties of the food which they contact
(Partington 2003). Aluminium or stainless steel cans, casks or kegs, therefore, are lined
with epoxy lacquer coatings to prevent metal from leaching into the relatively low pH
beer.
Styles of beer
One fundamental approach to classifying beers is based on whether they are generated
by ‘top fermentation’ or ‘bottom fermentation’, i.e. whether the yeast congregates at the
top of the vessel or sinks to the base. In modern fermenters with their high hydrostatic
pressures the distinction is blurred. Top fermentation tends to be at relatively warm temperatures
(15–25°C) with the yeast producing higher levels of avour volatiles such as
esters, affording fruity characteristics. Bottom fermentation beers are produced at much
lower temperatures (e.g. 6–15°C) and frequently possess signi cant sulphury notes.
The main top fermentation beers are the ales. Alcohol content will generally be in
the range 3 to 7.5% by volume (ABV), and more frequently in the bottom half of the
range. The major grist material will be well-modi ed malt, kilned to relatively high
temperatures to impart a copper colour. ‘Mild’ is a sweeter, darker product, the colour
being either due to caramel or in part to a low proportion of heavily kilned malt, though
not so much as to impart burnt avours. It tends to have a lower alcohol content (less
than 3.5% ABV) and when bottled may be referred to as ‘Brown Ale’. ‘Barley wines’