Introduction to Winemaking Part 2: Must Additions

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Introduction to WinemakingPart 2 Must Additions

• Dr. James Harbertson
• Extension Enologist
• Washington State University

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Must Additions

• Must is the crushed fruit.
• Sugar
• Water
• Acid
• Sulfur Dioxide
• Yeast Inoculation and Nutrients
• Other additions..

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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 AOCs in France.

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Water Additions

• Water may also be added to dilute juice to a
  minimum of 22 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.

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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.

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Acid Additions II

• The magnitude of change from the addition is
  determined 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.

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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

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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.

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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

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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

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Free SO2 to achieve necessary molecular

• For wines pH 3.5-4.0 about 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.

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Bisulfite Functions

• Decolorizes anthocyanin by binding them
• 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.

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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.

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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.

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Other Additions.

• Enzyme Additions
• Tannin Additions

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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.

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Enzyme Additions II

• Enzyme cocktails
• 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

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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