Transcript The Practice and Chemistry of Wine Making

The Practice and Chemistry of
Wine Making
Ron Bihovsky
www.keysynthesis.com
Chemical Consultants Network
January 2017
Outline
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History of winemaking
Grape cultivars
Yeast strains
The winemaking process
Chemistry of wine
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Fermentation of sugars to ethanol
Acids
Tannins
Tastes (Aromas) – Good and bad
Phenols
Color of wine
• Tasting
History of Wine-Making
• The earliest known evidence of wine comes from
Georgia (Caucasus), where 8000-year-old wine jars
were found.
• In the Bible, grapes are first mentioned when Noah
grows them.
• “Noah, a man of the soil, planted a vineyard. He drank
of the wine, got drunk, and he lay uncovered in his tent.”
‫ויחל נח איש האדמה ויטע כרם‬
‫וישת מן היין וישכר ויתגל בתוך אהלו‬
(Genesis 9:20–21)
Yeast Ferments Sugars of Grapes
to Ethanol
Sugars:
Saccharomyces cerevisiae
(Yeast)
Glucose
2 CH3CH2OH
Ethanol
+
2 CO2
Carbon Dioxide
Fructose
700 different strains of Saccharomyces cerevisiae have been identified
Grape Cultivars
Hundreds of Vitis vinifera grape varieties used for wine making
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Cabernet Sauvignon
Cabernet Franc
Merlot
Grenache
Zinfandel
Shiraz
Petit Sirah
Syrah
Montepulciano
Malbec
Sangiovese
Pinot Noir
Barbera
Valpolicella
Concord: Vitis labrusca
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Sauvignon Blanc
Riesling
Chablis
French Colombard
Chardonnay
Soave
Gewurztraminer
Pinot Grigio
Muscat
Chenin Blanc
Catawba: V. labrusca + V. vinifera
Grapes
Usually from California
Removing the Stems
Crushing the Grapes
The Old-fashioned
way
Yeast
You Don’t Want to Make Vinegar
Acetobacteraceae
Sugars
O2
CH3CH2OH
CH3CO2H + H2O
Acetic Acid (Vinegar)
Prevent vinegar formation by
• Sterile Conditions
• Excluding oxygen
• Adding K2S2O5 (potassium metabisulfite) or KHSO3
(potassium bisulfite), sources of SO2 (sulfur dioxide), to kill wild
yeast and bacteria. <350 ppm. Does not cause headaches.
Primary Fermentation
Wine Press Removes Skins and
Seeds
Secondary Fermentation
Sediment Settling
Decant Wine From Sediment
Age in Oak Barrel or
with Toasted Oak Chips
Decant Again and Bottle
Nasty Aromas (Faults)
H2S
S
SH
Hydrogen sulfide
Ethanethiol
Dimethyl sulfide
NH2
O
CO2H
O
CO2Me
Butyric acid
Ethyl acetate
HO
Cl
Cl
HO
MeO
MeO
Guaiacol
Smoky
Methyl anthranilate
Concord grapes
Cl
4-Ethylphenol
Brettanomyces yeast
2,4,6-Trichloroanisole
Moldy cork + Cl
Acids – Tart: pH ~ 3.5
OH
CO2H
HO2C
CO2H
HO2C
OH
Tartaric Acid, pKa = 2.89
Precipitates from Wine
Succinic Acid, pKa = 4.21
CO2H Lactic acid bacteria
HO2C
OH
Mallic Acid, pKa = 3.41
-CO2
O
OH
Lactic Acid, pKa = 3.86
CO2H
HO
H3C
CO2H
Acetic Acid, pKa = 4.76
CO2H
CO2H
HO
OH
Gallic Acid, pKa 4.5
Antioxidant
Pyruvic Acid, pKa = 2.50
Tannins – From Skin and Seeds
Astringent in red wine from grape seeds and skin
Phenols
Slightly Bitter and Persistent
OH
O
HO
OH
OH
O
HO
OH
OH
OH
OH
OH
O
Quercitin (Flavonol)
Catechins (Flavanol)
OH
HO
(HO)
CO2R
HO
OH
Resveratrol
(Hydroxy)cinnamic Acids
Esters with Tartaric Acid
Color of Red Wine: Anthocyanins
OH
O
H+
O
HO
+
O
HO
OH
OH
O-Glu
O-Glu
O-Glu
O-Glu
Cyanidin-3,5-O-diglucoside (Purple, pH 6)
Cyanidin-3,5-O-diglucoside (Red, pH <3)
Anthocyanins: Present in grape skins
During aging, anthocyanins react with tannin and other molecules to form
more complex molecules with red colors
Which eventually become insoluble and precipitate
Pleasant Aromas (Flavors)
OMe
HO
O
HO
O
MeO
MeO
Vanillin
Oak
O
O
Syringaldehyde
Oak
HO
HO
MeO
MeO
Ethylguaiacol
Smoky
Diacetyl (2,3-Butanedione)
Buttery
O
Eugenol
Clove
O
Whiskey Lactone
Oak
O
SH
(E)-ß-Damascenone
Rose Smell
O
4-Mercapto-4-methyl-2-pentanone
Cat Urine