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Chemistry of wine-making

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Anna Marie Coicheci

on 25 May 2014

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Transcript of Chemistry of wine-making

Chemistry of wine-making
Spraying plants with fungicides such as a copper sulphate (
) removes hydrogen sulphide (
) from the vines, avoiding mildew called
from rotting the leaves.

Sulphites occur naturally in wine and can also be added to the wine to help stabalise it as it ages and to kill bacteria. Without sulphites the wine can turn into vinegar within months.

Sulphites may be chemically removed by
the wine or by adding a little
hydrogen peroxide
since many people are allergic to them.
primary fermentation
the grapes are crushed and
are added to convert
in the grape juice (
) into alcohol (
) and carbon dioxide (

Each gram of sugar that is converted, half a gram of alcohol is produced. To achieve a 12% concentration, must should contain about 24% sugars. The sugar percentage of the must is calculated using a

The wine is pumped into tanks where the skins are pressed to extract remaining juices and kept warm for remaining sugars to convert into alcohol and CO2.
Cold and heat stabilisation
Cold stabilisation
process is used to reduce the tartrate crystals (
potassium bitartrate
) that are formed in the wine by
tartaric acid
and looks like a

Dropping the temperature of the wine will cause these crystals to stick to the vessel, so when the wine is drained the crystals are left behind.

Heat stabilisation
causes unstable proteins to be removed by adsorption onto
, a powder that turns to clay, preventing them from
into the bottled wine.
Sunshine and rainfall
Grapes need between 1300-1500 hours of sunshine during the growing season and around 690 millimeters of rainfall.

Hillsides and slopes receive a greater intensity of sun rays, and allow for better water drainage so that the roots don’t rot.
Starting with chemicals found in soil

Ammonium ion
Nitrate ion
Copper(II) Sulphate solution
Peronospera forming on a leaf

Vinification - the wine-making process - involves
secondary fermentation
, and
heat stabilisation

Primary fermentation
secondary fermentation
malolactic bacteria
is added to convert
malic acid
lactic acid
which is a milder acid softening the taste of the wine.

From here, the wine can be transferred to
stainless steel tanks
oak barrels
to mature. This is where wine, especially red wine gets its oak aroma.
Secondary fermentation
After the wine has matured the yeasts are removed by filtration.

Variations, such as removing yeast earlier on, leaves sugars behind making a sweeter wine.

Filtrating wine also prevents microbial spoilage, and SO2 may be added as a preservative, ready for bottling.
tartrate crystals on a cork
Bram. L. L. Dickey. N. H. (1979) Funk & Wagnalls New Encycolpedia. Wine. Vol. 27. Pages 332 to 336

Wikipedia. (2014. March 7). Viticultutre. Retrieved from: http://en.wikipedia.org/wiki/Viticulture

Wineanorak. (2011. August). Retrieved from: http://www.wineanorak.com/howwineismade.htm

Hewitt. H. W. Palate Press LLC. (2012. February 29). Much Ado About Sulfites, French Wines, and Organic Regulations. Retrieved from: http://palatepress.com/2012/02/wine/much-ado-about-sulfites-french-wines-and-organic-regulations/

The Vintner Vault. (2014). Where the wine industry shops. Retrieved from: http://www.thevintnervault.com/index.php?p=w_m_tips&id=5781

Urban wine grower. (2014). Grow a grape vine. Retrieved from: http://urbanwinegrower.wordpress.com/grow-a-grape-vine/

Rodriguez. S. (2013. August 29). Wine Field picture. Expensive Wine vs Cheap Wine – What’s The Real Difference?. : Retrieved from: http://www.wine-rack-depot.com/expensive-wine-vs-cheap-wine-whats-the-real-difference/

Anpros Pty Ltd. (2014). Copper sulphate solution: Retrieved from: http://www.anpros.com.au/laboratory-reagents/copper-sulphate-solution/

Wikipedia. (2006. April 15). Amoni: Retrieved from: http://commons.wikimedia.org/wiki/File:Amoni.png

Google images. Fermentation saccharometer: Retrieved from: https://www.google.com.au/images?q=saccharometer&hl=en-AU&gbv=2&tbm=isch&ei=_MtUU8m3HMiHkAWR64DgDA&start=0&sa=N

Mills. B. Wikipedia. (2007. August 31). Nitrate ion with partial charges: Retrieved from: http://en.wikipedia.org/wiki/File:Nitrate-ion-with-partial-charges-2D.png

Microbe Wiki. (2012. December 12). Vinification. Mic processes: Retrieved from: https://microbewiki.kenyon.edu/index.php/File:Mic_processes_2_MLF.jpg
is present in the form of nitrate (
) and ammonium (
) ions – it travels to grapes and leaves.
Too much nitrogen results in heavy leaf growth creating unwanted shade over the vine, and too little produces
hydrogen sulphide
, giving a rotten smell.
protects plants from drought and disease and produces grapes higher in sugar.
Hydrogen sulfide
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