Agriculture Reference
In-Depth Information
However, although it is a permitted additive in many countries, including Australia,
New Zealand, South Africa and the US, its use is treated with some caution by
many winemakers in many countries as far as wine is concerned. The caution arises
from the ability of ascorbic acid to reduce quinones (oxidised polyphenols that
cause browning in white wine) - a good thing; but in doing this it produces the
by-product H
2
O
2
(a potent oxidising agent) when sulphite levels are too low - a
bad thing. Also at higher sulfi te levels it can oxidise sulphite to sulfate. Indeed,
ascorbic acid has been shown to be both an antioxidant and an oxidant in
model white wine solutions, depending on its concentration compared with that of
free sulfi te (Bradshaw
et al.
2004). Nevertheless, it is generally recommended
for use alongside sulphites (≤100 mg/l) and is most often employed in the prevention
of pre-fermentation oxidation (at ∼5 g/hl of must) for protection of wine
against ferric haze and for minimising 'bottle sickness' after bottling (McKay
et al.
2011e).
Natamycin (pimaricin or pimarizin), a natural product derived from
Streptomyces natensis
, is an antifungal (but not antibacterial) agent that is
permitted as a wine preservative for use in Argentina and South Africa, but not in
most other countries, such as Australia, Canada, EU Member States, New Zealand
and the US (McKay
et al.
2011e), despite the fact that it is allowed in the
preparation of certain cheeses and hams in some of these states, and has been
awarded GRAS status in the US. Its major advantages are its effi cacy at low levels
(∼10 mg/l), its pH tolerance and its low toxicity (which also applies to natamycin's
decomposition products). No carcinogenic, mutagenic, teratogenic activities or
allergenic properties have been noted (JECFA 2002).
16.3.3 Antifoaming and foaming agents
Antifoaming agents are added to beer wort at the fermentation stage so that
fermentation vessels may be fi lled to greater capacity, thus increasing turnover.
The most common permitted types are synthetic polysiloxanes (silicones), but on
a pilot plant scale, long chain unsaturated fatty acids have been found to be effective
subduers of foam; thus, C12 to C14, C18:1 and C18:2 acids all reduced foam
stability and the surface elasticity of beer (Wilde
et al.
2003). In brewing, however,
foam destabilisers should be removed entirely before the packaging stage, whether
or not foam enhancers (see next paragraph) have been employed. Although
the use of unsaturated fatty acids (or oils containing them) is rare in brewing,
it has been noted that yeast stored mixed with olive oil and used to ferment non-
aerated worts gave beers of greater fl avour stability than beers brewed by a
conventional method (Hull 2007). These fi nished beers also had normal foaming
characteristics, indicating that all the oil components had been removed during the
process.
Unlike foam destabilisers, natural foam enhancers (foaming agents) are
frequently used in the brewing industry, but even here the most common agent is
probably the synthetic propylene glycol alginate. Cereal adjuncts such as rice,
maize grits and corn syrups are used as partial replacement of malted barley in the
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