Délestage is a rack-and-return process modified to deport seeds, illustrated here. Fermenting
juice was deported from a bottom valve through a dejuicing sleeve with holes 1/10-inch in
diameter. Seeds were retained within the sleeve, and the deported juice was pumped to a
separate tank while the cap was allowed to drain. Process was conducted once per day until
the completion of fermentation or dejuicing, depending on the particular trial.
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themust temperature, and
added to each lot (24 g dry yeast/100 L).
The six equal-weight lots were randomly
assigned to treatments consisting
of 1) control, conventional fermentation,
with cap manually
punched down two times per day, or
2) délestage, consisting of a rack and
return procedure with seed removal
conducted once per day until dryness,
as follows.
Following cap rise, fermenting juice
was drained from a bottom valve
through an external cylindrical dejuicing
sleeve (2.39 mm diameter holes)
into a stainless steel vat. Seeds were
retained within the sleeve.
The juice was pumped to a separate
tankwhile the dejuiced capwas allowed
to drain freely for two hours. Juice was
then returned to the top of the cap via a
tank cap irrigator, using deflection plates
to minimize skin breakage. The separated
seeds were drained free of liquid,
weighed, and discarded.
Treatment and control vessels
averaged filled height-to-diameter
ratios of 0.64 and 0.75 for the
délestage and conventional fermentations,
respectively.
Fermentations were conducted at an
average liquid temperature of 28°C
(range 26° to 35°C) and an average cap
temperature of 30°C (range 28° to 37°C)
in 1,000-L capacity vessels. Pressing was
performed at dryness (2.0 g/L reducing
sugar) using a tank press to 1 bar. Freerun
and press-run wines were combined.
Juice was brought back to top of the
fermentation tank using a cap irrigation
system. Délestage, therefore, involves two
main features which are impacting the
tannin profile of the wine (and therefore
the structural/textural qualities):
1) removal of seeds could reduce the
contribution of immature phenols;
2) oxidative polymerization could result in
partial reduction of monomeric pigments as
they are incorporated into large polymeric
pigments.
(For more details see www.icv.fr/
kiosqueuk/procedur/delestage.htm or
www.vtwines.info/enologynotes/
onlinepublications)
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Tannins in the skins and seeds can
combine with anthocyanidin glycosides
(anthocyanins) to form polymeric pigments.36
These pigments are believed to
be formed by condensation products of
malvidin-3-glucoside and various procyanidins
created through acetyl
bridges.9,26 Anthocyanin-tannin complexes
can be produced by binding
between the C-4 of the flavylium salt
and the C-8 of catechin.21,27
D.O. Adams et al. reported extractable
seed tannins in Syrah grapes
declined by about half from véraison
to harvest, and were about three times
greater than skin tannin concentrations.2
Grape skin phenols are more
easily extracted during fermentation
than those of seeds and stems.18
Although skins contain a lower
concentration of total and polymeric
phenols than seeds,13 they may be the
primary source of polymeric phenols
in wine.14 For the first five to seven
days of fermentation, phenolic compounds
are extracted mainly from
skins, followed by extraction from
seeds.23
Several reports have suggested that
seeds contribute significant concentrations
of proanthocyanidins to wines,15,29
while others have reported the seed
contribution to be limited.4,24,39 These
contradictory observations may be the
result of differences in cultivar, fruit
maturity, and winemaking style.
For example, duration of maceration
primarily influences the extraction
of phenolic compounds from the
seeds,40 while fermentation temperature
appears to be a primary factor
influencing extraction from skins.23
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Délestage, or rack and return, is a
maceration technique designed to help
optimize the exchange between the liquid
and solid phase by emptying the
fermentation vessel of liquid while
aerating the juice.
Following several hours of cap
draining, the liquid is gently pumped
over, or returned, to the cap. This procedure
is designed to help oxygenate,
while minimizing mechanical grinding
of the skins, seeds and stems
(Dominique Delteil, personal communication,
2003). This study evaluated
délestage in conjunction with
partial seed removal, to determine
the impact on Merlot wine composition
for three seasons and on
Cabernet Sauvignon for one season.
Materials and Methods
MERLOT fruit (approximately 8,500
kg), grown in central Virginia, was
hand-harvested in each of three years
at a minimum of 21.0° Brix (a common
soluble solids concentration for Merlot
grown in central Virginia). Fruit was
immediately destemmed, crushed, and
divided into six equal-weight (1,416
kg) replicates. Must fermentable nitrogen
levels were measured,10 and
adjusted to 250 mg/L adding either
Fermaid K™ (Scott Laboratories, Petaluma,
CA) or Superfood™ (The Wine
Lab, Napa, CA). Sulfur dioxide (30
mg/L) was added at crush to each lot.
Each must was given a cold maceration
(cold soak) period of 24 hours at
10°C, prior to fermentation. D-254™ yeast
(Scott Laboratories, Petaluma, CA) was
hydrated, microscopically examined for
budding, viability and purity, cooled to
within 3°C of
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