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Australia's Secret ? Enological Tannins
Australia's secret ? :
Volume X Number 6
Wine Industry Workshop
Australia's Red Secret and
By David Falchek
at the 32nd Annual New York Wine Industry Workshop in Geneva, New
York braved a late-season ice storm in April to discuss topics of
warmer times: winemaking.
Sponsored by the Cornell Wine Research and Extension Program and
the New York Wine & Grape Foundation,
the three-day event drew over 300 participants from across the
continent and speakers from around the globe.
program included uses for enzymes and oenological tannins, new
methods for malolactic fermentation, and a discussion of what could
be the next big regulation--limiting the amount of histamine permitted
The secret behind the ability of Australian
reds to so quickly claim a place in the international market is
oenological tannins, said Scott Lab's Diane Burnett. Scott's representative to
Australia sells heaping truckloads of tannin Down Under, Burnett
said. Bordeaux winemakers use oenological tannins, though don't admit
it. Yet US winemakers are slow to embrace the easy, and easily
reversible, process, Burnett noted.
reason Australian reds are so approachable and drinkable sooner, is
because of the tannins," she said.
winemakers in hot, high-sugar growing regions where grapes rarely
achieve phenolic maturity--such as Texas, Colarado and the Central
Valley--are adopting the mantra "harvest early, add
tannins may seem costly when using it by the pound, Burnett said the
cost for small producers is between three and seven cents per case.
Beringer Blass Wine Estates senior
research enologist Tom Collins discussed
tannin's conventional role of color stability and wine quality. Christophe Gerland, a consultant withItell'oeno, in France followed with new roles
for tannins--from preventing oxidation to promoting riddling.
sees the rich purple juice coming from the crusher destemmer, it's
natural to wonder at bottling, or a year or two later, where all that
color went. That color comes from Anthocyanin compounds. A fickle
bunch not cut out for the excitement of fermentation or the boredom
of the bottle, anthocyanins prefer to just drop out. The key to
keeping anthocyanins at the party is to get them to hook up--with
this polymerization doesn't always happen, or happen enough, in red
fermentations. Anthocyanins are in grape skin. Water soluble, they
are easily liberated into the must, as one can see during crush. The
first few days, they are everywhere. Tannins arrive at the
fermentation ball later, extracted in significant numbers after two
or three days. But by then, most anthocyanins have precipitated away
like Cinderella at midnight.
oenological tannins, winemakers can become matchmaker, getting
tannins and anthocyanins in the same place at the same time. Collins
found the best way to do that is to add enological tannin before,
during and after fermentation in multiple, small doses. He applies
between 50 and 75 ppm several times over the course of three days for
a total of 100 to 200 ppm. The polymerization that follows provides
color stability, adds structure and mouthfeel, and imparts oak
post-fermentation dose, the one most likely to improve structure and
mouthfeel, is tricky, however. To allow for tannin precipitation and
polymerization, filtering is best put off for days, or weeks if
said that through the last decade in Europe, research into tannin
additions and use in the cellars has dramatically increased and found
applications in white and sparkling wine. Winemakers have assembled
tannin sources beyond grapes and oak and found a range of benefits
that make them sound almost like huckster's cure-all. Grape tannins
are expensive. Less costly tannin sources from exotic woods or nuts
are in some cases more effective than grape tannins.
whites, tannins help prevent oxidation. Gallic tannin derived from
soybeans prevents oxidation in grapes that are botryitisized or that
have a low polyphenol content. Tannin additions allow winemakers to
safely cut back on SO2 additions. Reduced sulfur compounds can
be eliminated by 50 to 100 ppm of the chestnut-derived tara tannin,
which works with oxygen to remove sulfur. The chestnut tannins when
added at 100 ppm aids fining by promoting the flocculation of
gelatins. Oak tannins enhance the structure of whites, offering
slightly wooden aromas at applications from 20 to 100 ppm. But
Gerland sees a range of results from different commercial oak tannin
preparations and urged careful blind bench trials.
tannins may be employed in sparking wine production with 50 ppm of
chestnut tannins at the end of malo-lactic fermentation to improve
structure and riddling for later triage. Then a combination of
chestnut and oak tannins at 30 to 50 ppm is added with the dosage. At
disgorging, 30 to 50 ppm of oak tannins adds mouthfeel and aroma.
must, tannins help augment the tannins in low maturity grapes while allowing
the winemaker to reduce maceration time, which in the case of unripe
grapes can extract nasty green tannins. Quebracho tannin, derived
from the tree in Central and South America, provides structure and
stabilization at rates of 100 to 400 ppm. Ellagic tannins are able to
protect color during aging and prevents oxidation. A combination of
quebracho and ellagic tannins added in two doses--on the must and
after fermentation--give better color and taste.
Enzymes are maceration's exclamation point.
Whatever is in the fruit will be drawn out by enzymes, stressed Widmer Wine Cellars winemaker Glenn Curtiss and Gerland in their
Curtiss is winemaker at Widmer in Naples,
NY, a long-standing piece of Constellation Brands'
now-global empire. There, Curtiss makes a combination of bulk and
small batch "boutique" wines. He's found enzymes useful in
increasing quantity and quality for all styles.
enzymes, typically a mixture of several enzymes, are most commonly used
as pectinase to break down grape cells and increase juice yield and
filterability. Curtiss found enzymes increase the volume of his
labrusca crush up to 5 percent. Vinifera crush increased two to three
percent. Beyond gallons, the act of dissolving the cells of the grape
wall extracts anthocyanin and tannins to increase color and
enzyme preparations can have other beneficial side effects, Curtiss
said. In wines such as Riesling, Viognier, and GewÃ¼rztraminer,
beta-glucosidase frees aromatic compounds called terpenols from
sugars so they can be perceived by the senses.
sees a brand difference in some enzymes--particularly those that
claim side activities--he said winemakers who want them solely for
depectinization may purchase based only on price.
trials are a must. For example, Curtiss' Pinot Noir comparisons
showed that half the 30 gram per ton standard dose of EVG extracted
more color and was twice as likely to be the preferred by a tasting
discussed how white grape cold soak has been combined with enzymes to
obtain more full-bodied and aromatic wines. Echoing Curtiss, Gerland
found extraction enzymes, between 2 and 4 grams per 100 kilograms
soaked for six hours, not only increases juice volume, but also the
aroma and roundness of the wine. Enzyme protocol, however, is
changing. Instead of adding aromatic enzymes at the end of
fermentation, more European winemakers add them at the front end,
before cold soak. They have learned that beta-gludosidase enzymes, mixed
with macerating enzymes and added at cold soak, yield greater
aromatic intensity, reveal norisopreniods, and increase overall wine
quality. Gerland said the two enzymes appear to work in synergy.
Muscat, GewÃ¼ztraminer, and Riesling clearly benefit, however,
low-aromatic grapes such as Chardonnay, Ugni Blanc, and Muscadet also
are hardly a magic bullet, both speakers noted. Used improperly, they
can backfire. Grape maturity is critical for enzyme use in reds,
Gerland stressed, with several French studies showing that extraction
of tannins and anthocyanins, fruity aromas, and color are greater in
optimally ripe grapes. In grapes that aren't mature, enzymes increase
stringency and vegetal aromas.
also cautioned the audience to avoid enzymes containing
cinnamoyl-esterase activities particularly for long-aging reds or
barrels-destined wines where Brettanomyces risk is high. Enzymes that
bill themselves as "purified" tend to be free of
A New MLF
Of all the processes of winemaking, one of
the least understood is malolactic fermentation. In some cases, even
by-the-book winemaking results in failed MLF. One explanation,
said Sibylle Kriegerof Lallemand Inc., is a combination of
substances in wine that inhibit ML such as SO2, alcohol and pH.
Several experiments by Thomas Henick-Kling, enologist at Cornell,
show that a simultaneous inoculation with yeast and ML culture can
help guarantee the completion of ML before the accumulation of
inhibitory substances, Krieger said.
of yeast used is critical. Yeast known as big SO2 producers and
nitrogen consumers shouldn't be used in any must meant to undergo any
MLF. The K1 yeast strain is a prodigious SO2producer while 71B and
WÃ¤denswil produce much less and are most favorable for MLF. Musts
hosting a yeast that is both nitrogen-hungry and SO2-producing is
almost unable to undergo any MLF.
starter culture with yeast inoculation seems to violate an old
winemaker rule--MLF in the presence of sugar will yield acetic acid.
However, Krieger said other research has shown that excessive acetic
acid will not be produced so long as yeast fermentation is strong,
healthy, and goes to completion. The greater concern is that MLF will
inhibit yeast fermentation. Initially, the yeast and ML bacteria both
compete for the available nutrients in the must. The ML bacteria
sustain themselves as the yeast flourish for the first ten to 20 days
of fermentation. The dying yeast cells return nutrients to the must
and the ML bacteria dominate.
No one knows for sure why, but a greater
number of people are having adverse reactions to histamines, a
ringleader in a group of substances known as biogenic amines that
occur in many foods. Jurg Gafner has
studied the issue at the Federal Research
Station in WÃ¤denswil, Switzerland, where a law
limits biogenic amines in wine to no more than 10 ml/l. France,
Belgium and Germany either have laws on the books or in the works
limiting biogenic amines in wine to lower levels.
is not a topic in the US yet, but you need to be one step ahead of
regulators," Gafner said. "Biogenic Amines could be an
export barrier in the future."
amines result from the decomposition of protein and are common and
expected in aged cheeses and sausages. Regulators already use
biogenic amines to determine the freshness of fish. People with
histamine intolerance react drastically after consuming histamines,
with itching, headache, nausea and difficulty breathing. While many
foods have histamines, alcohol consumption reduces the body's ability
to degrade histamine.
Gafner said biogenic amines don't belong in
wine. They are a by-product of spoilage microorganisms. Sanitary
winemaking practices are the best way to keep them at a minimum.
Amines are closely linked the activity of the bacteria Pedicoccus damnosus and Brettanomyces.
A vigorous, continuous alcoholic
fermentation with a commercial yeast, and inoculation with an ML
starter culture that does not form amines will reduce total amines in
David Falchek ,
based in Pennsylvania, covers the East Coast wine scene for the
Finger Lakes Times, and others. He is available via his email
address firstname.lastname@example.org .