Transcript Introduction to Winemaking Part 2: Must Additions

Introduction to Winemaking
Part 2: Must Additions
Dr. James Harbertson
Extension Enologist
Washington State University
Must Additions
• Must is the crushed fruit.
• Sugar
• Water
• Acid
• Sulfur Dioxide
• Yeast Inoculation and Nutrients
• Other additions..
Sugar Additions
• Sugar additions are allowed in WA
 Concentrate or pure sugar, or other fruit
 Additions cannot change final Brix past 25.
• Can be added after fermentation or before
• Process is known as chaptalization, after the French
man who popularized it, Jean-Antoine Chaptal.
• Regulated in most countries
• Illegal in CA and Oregon.
• Legal in some AOC’s in France.
Water Additions
• Water may also be added to dilute juice to a minimum of 22
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Brix
This can be done in the form of fermentation facilitation, or
equipment flushing
Can be done pre or post-fermentation.
Primarily done to lower eventual EtOH concentration.
Reverse osmosis used to reduce EtOH but very costly.
Better to not make mistake at the outset.
Acid additions
• In practice it is done to reduce the pH and increase
the titratable acidity.
• Tartaric acid and malic acid may be added to
fermenting juice.
• Tartaric is the best choice because it is microbial
stable.
• For reds done early about a day after skin contact
because of high potassium content of skin.
Acid Additions II
• The magnitude of change from the addition is determined
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by the buffering capacity of the must.
The increase in TA will be due the difference in the
magnitude of the addition and the loss of K2TAR.
The pH change will also be dependent upon the buffering
capacity of the must.
In practice additional acid is used to achieve a targeted
value.
Acid of known concentration is added to a representative
sample and monitored on a pH meter.
Sulfur Dioxide
• Inhibits and kills native yeast and bacteria
• Inhibits oxidative enzymes that cause browning
• Decolorizes anthocyanin pigment
• Interacts with phenols in the competitive
oxidation
• Delays non-enzymatic browning
Chemistry of Sulfur Dioxide
• SO2  HSO3-
pKa = 1.86
• SO2 known as the molecular form
• HSO3- known as the bisulfite form
• Each form reacts differently based on its own
specific chemistry.
Molecular Form Functions
• Inhibits oxidative enzymes
 Behaves as competitive inhibitor
• Kills wild yeast and bacteria
• Effective hydrogen peroxide trapping agent.
• Is volatile and detectable by sensory
 Pungent metallic odor
• Is lost due to its volatility
How much is necessary?
• From 25 mg/L to 75 mg/L SO2 required to inhibit from
75 to 97% of PPO enzyme.
• Laccase a more potent oxidative enzyme found in
Botryized fruit requires 150 mg/L (too much).
• 0.825 mg/L molecular SO2 is necessary to reduce
viable cell population by an order of magnitude (10X).
• Assumed that addition for enzyme reduces microflora
significantly enough if you are inoculating
Free SO2 to achieve necessary
molecular
• For wines pH 3.5-4.0 about
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Free SO 2 for 0.825 mg/L
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45-150 mg/L free SO2
necessary for 0.825 mg/L
molecular.
Equation can be used for
specific cases.
Just plug in your pH to
equation and the free SO2
will be calculated.
160
140
y=
0.0187e2.2278x
R2 = 0.99
120
100
80
60
40
20
0
2.50
3.50
pH
4.50
Bisulfite Functions
• Decolorizes anthocyanin by binding them
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 Disrupts conjugated system
Is easily covalently bound by acetaldehyde, keto-acids and
sugars.
Bound form disrupts normal equilibrium.
Establishes new equilibrium of bound and free.
Makes estimation of sulfur dioxide difficult.
Forces methodologies to measure bound and free sulfur
dioxide.
Current methodologies have problems estimating bound
and free form because of differential disassociation
constants of bound forms.
Yeast and Yeast Nutrients
• Grape juice fermentations are done by a strain of
Saccharomyces cerevisiae.
• They can happen naturally (native yeast that live in
the winery), or by inoculation with a commercial
strain.
• Use of sulfur dioxide and inoculation generally
minimize the influence of wild yeast(s) on wine
quality.
Yeast and Yeast Nutrients II
• Inoculation can occur any time after crushing but
is usually done after other additions are complete
• Yeast nutrients are generally included in the
inoculation step as a safeguard for stuck
fermentations.
• Yeast nutrients include ammonium salts, amino
acids and vitamins.
• Not all musts require nutrients but it is easier and
cheaper for smaller wineries than having to
analyze everything.
Other Additions….
• Enzyme Additions
• Tannin Additions
Enzyme Additions
• Direct additions (not on fixed bed)
• Sensitive to temperature, EtOH and SO2
 Pectinase-Juice yield enhancement enzymes
• Also helps prevent hazes in wines
 Glucosidase-Freeing bound volatile compounds
• Muscat, Riesling, Gewurtz. contain bound terpenes that
can be freed to enhance aroma by using enzyme
 Glucanase-Break down colloids that foul filter
• Botrytis infected grapes contain colloids that will foul
filter and enzyme addition can help.
Enzyme Additions II
• Enzyme cocktails
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 Contain peptidase (small proteins), protease (breaks
down protein), pectinase, glucosidase activity
Used to help extract color and tannin from skins and will
also facilitate tannin seed extraction
Breakdown cell wall of skin and seed to facilitate
extractions.
Product does not always work
Window of opportunity for enzyme addition is vague.
Can make mush out of your cap
Tannin Additions
• Done to modify astringency and help stabilize color
• Many different products
• Mixture of tannins from different species.
• Different species have tannins that are different than
found in grapes.
• Unclear whether additions are beneficial (Tannin
addition products also contain volatile compounds that
modify wine aroma as well)
• Laws allowing additions are vague and need to be
updated