1. The Practice and Chemistry of Wine Making
Ron Bihovsky
Chemical Consultants Network
January 2017

2. Outline History of winemaking Grape cultivars Yeast strains
The winemaking process
Chemistry of wine
Fermentation of sugars to ethanol
Acids
Tannins
Tastes (Aromas) – Good and bad
Phenols
Color of wine
Tasting

3. 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)

4. Yeast Ferments Sugars of Grapes to Ethanol
Saccharomyces cerevisiae (Yeast)
2 CH3CH2OH CO2
Glucose
Ethanol Carbon Dioxide
Fructose
700 different strains of Saccharomyces cerevisiae have been identified

5. Hundreds of Vitis vinifera grape varieties used for wine making
Grape Cultivars
Hundreds of Vitis vinifera grape varieties used for wine making
Cabernet Sauvignon
Cabernet Franc
Merlot
Grenache
Zinfandel
Shiraz
Petit Sirah
Syrah
Montepulciano
Malbec
Sangiovese
Pinot Noir
Barbera
Valpolicella
Concord: Vitis labrusca
Sauvignon Blanc
Riesling
Chablis
French Colombard
Chardonnay
Soave
Gewurztraminer
Pinot Grigio
Muscat
Chenin Blanc
Catawba: V. labrusca + V. vinifera

6. Grapes Usually from California

7. Removing the Stems

8. Crushing the Grapes The Old-fashioned way

9. Yeast

10. You Don’t Want to Make Vinegar
Acetobacteraceae
Sugars
CH3CO2H + H2O O2
CH3CH2OH
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.

11. Primary Fermentation

12. Wine Press Removes Skins and Seeds

13. Secondary Fermentation

14. Sediment Settling

15. Decant Wine From Sediment

16. Age in Oak Barrel or with Toasted Oak Chips

17. Decant Again and Bottle

18. Nasty Aromas (Faults)

19. Acids – Tart: pH ~ 3.5

20. Tannins – From Skin and Seeds
Astringent in red wine from grape seeds and skin

21. Phenols Slightly Bitter and Persistent

22. Color of Red Wine: Anthocyanins
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

23. Pleasant Aromas (Flavors)