Jessica Weber

CBE 555

Spring 2008

Background InformationStages of production

White vs. RedReactions

Role of Acids/controlling pHQualityProblems that ariseNext StepsQuestions

e·nol·o·gy also oe·nol·o·gy       (ē-nŏl'ə-jē) n.   The study of wine and the making of wine; viticulture.

Wine Production CategoriesStill Wine Production (without carbonation)

Alcohol concentration is about 7-14%Sparkling Wine Production (with carbonation)

Use grapes with a lower sugar levelFortified Wines (higher alcohol concentration)

Alcohol concentration is about 14-30%

Wisconsin produced 375064 tons in 2004 accounted for .1% of total production in US.

U.S. yearly per capita consumption of wine is 12 liters, up from 10.6 liters in 2000

HarvestThere are over 4000 varieties of grapes used in the

production of wine.Grapes are usually harvested from early September to the

beginning of November.

Grape Selection/Processing Grapes must be treated with 50-75 ppm of free sulfur

dioxide. Sulfating is done to remove unwanted bacteria before the next step of the process.

Equipment must also be sanitized. This is usually done with an O2 based caustic solution, water, and then a anti-bacterial sulfite solution. Finally another water rinse.Approximately 10 gallons of quality water are used for

every gallon of wine.

WhiteWhen processing grapes for White wine, after the

cleaning process they are immediately pressed and the juice is sent to the tanks (by pump or gravity fed).

Historical Press

As the pressure of the machine increases so does the amount of tannin pressed from the skins. Usually the pressure is kept between zero and 2 bar.

Modern Day Press

WhiteFermentation temperature is usually about 15-

18°CSweet wine are made by leaving some residual

sugar after fermentation This is done by:

Harvesting laterFreezing the grapes to increase the sugar

concentrationKilling the yeast before fermentation is complete

Red Grapes are usually crushed with all parts together and they

then go straight to fermentation The skin and seeds are important to pass on tannins and the

bitter taste unique to red wine – this mixture is called “must” Fermentation process is usually quicker for red wines

This is because red wines can be fermented at a higher temperature due to the nutrients it contains.Fermentation temperature is usually 22-25°C

Grape Crusher

RedThe fermentation process for Red wine is initially

open to the airAfter the must is transferred to the fermentation

tanks a “cap” is formed which prevents air from reaching the juiceThe cap is created by the solids that are pushed to the

top due to the carbon dioxide productionThis cap is kept in contact with the juice as much as

possible in an effort to retain the color and tanninsThis is done by punching the cap down manually or by

pumping the cap over mechanicallyThis process is done approximately twice a day

Once the juice has been transferred to the fermentation tanks, the yeast is added and the oxygen is removed. By removing the oxygen from the tanks, the

oxidation process is halted, which helps prevent any bacteria growth.

YeastSaccharomyces cerevisiae is the species of yeast

used in the fermentation process. This yeast species has been acclimated to the effects of

the free sulfur dioxide.Other species of yeast are intially present on the

grapes, however are killed in the cleaning process

Differences among fermentation processes Storage tank type

Some white wines will use wooden barrels to introduce a flavor into the wine

Conventional tanks are made of stainless steel Tank sizes can vary considerably, however commonly

are 300 to 1200 gallons

Fermentation Tanks

Length of process The fermentation process usually lasts 10-30

days. For red wines the process is shorter than for white wines

Temperature Fermentation is an exothermic process, so

temperature control is important Temperature is kept as close to 25 °C as possible to keep

the yeast in a “good” environment.

The aging process begins when fermentation is completeThe aging period is not a necessary step in

wine production, however it could last years if desired.

Aging is most commonly done in red winesAfter the aging process is complete the wine

is filtered and sent to be bottled

Many processes use cold filtration to remove as much sediment as possibleTemperatures are reduced to close approximately -

3°C for 1-2 weeksOften if this is not done and wines are stored cold,

settling can occur in the bottle – consisting of potassium acid tartrate

Also if the wine (White wines) is unstable it needs to be heat stabilized before the bottling processThis instability happens when certain proteins are

presentRemoved in the heat stabilization process by adsorption

to bentonite

After the cold filtration and stabilization processes the wine passes through large filters to separate dead cells and other sedimentsMade from: cellulose, paperCan use a gravity filter however this is a slow

process and the wine is exposed to air which induces the oxidation process

Wine then passes through smaller filters to remove and residual sedimentsUsually a membrane filter

Membrane filtration system

Right before bottling a small amount of sulfite is added to help preserve the wine and prevent further fermentation

Bottles are sealed using a cork, the air in the head space is removed immediately before inserting the cork Heat shrink capsule is then fitted over the cork

StorageBottles should be stored upright for about 3 days and then

at an angle or on their side in order to keep the cork wetIf the cork is not kept wet it can introduce air through the tiny

holes which can introduce oxidation/bacteria into the wineAlso the percent humidity can affect the performance of the

cork About 60% humidity it desired

Some wineries are switching to screw caps or synthetic corks in order to avoid this effect

Also bottles should be kept out of direct sunlightAs a precaution some wines affected by

sunlight are bottled in colored glass Sunlight exposure causes oxidation and the

breakdown of wine The optimal storage temperature for red and

white wines is about 55°F

Fermentation Process:C6H12O6 + yeast 2C2H4OH + 2CO2

The alcohol solution that results from fermentation contains about 12%-15% ethanol. This correlates to the conditions that yeast cells

can survive in, higher concentrations of ethanol will kill the yeast.

For every gram of sugar that is converted about a half gram of alcohol is produced.To achieve 12% alcohol concentration, starting

material must contain about 24% sugars.

Malo-lactic fermentation (secondary fermentation)Malic acid is converted into lactic acid and carbon dioxideChanges the flavor of the wine from crisp to creamy

buttery as well as reducing the amount of acidity (increases pH from .3-.5 units)

This can be introduced or happen naturally – and monitored by testing with paper chromatography.

Controlling the pH (best around 3.0-3.5)High pH results in less flavor production in the wineTo lower pH, tartaric acid is added at the beginning of the

fermentation process. Oxidation Reactions

Acetobactor bacteria will react with the oxygen to convert the wine into vinegar.

The quality of the wine is determined by the grapes and other starting material used

Quality is also affected by the weather during the growing season, the soil and the way they are pruned.

ProcessMechanical harvesting is usually

used for less quality winesClarification, stabilization, and

aging also contribute to the quality

During fermentation the most harmful bacteria that can grow is of the genus Acetobacter. However, this bacteria is sensitive to the free

sulfur dioxide, which is why the cleaning process is important.

Burnt match smell SO2 levels are greater than 40 ppm

Overly sweet wineFermentation can be restarted to convert the

residual sugar into alcohol

Hazy Colored wine can result from using iron, copper, zinc, or aluminum in the fermentation tanksIf it resulted from iron or copper a few drops of

citric acid will remove the hazeFiltering can also be done to remove the haze –

although this will also remove some of the tasteFining can also be used to reduce the cloudiness

of wineA fining agent is one that posses a charge (+ or -)

which can remove cloudiness with the opposite charge. Most commonly Gelatin (+), other agents include

animal/fish products, bull’s blood, PVPP (a dairy derivative protein) and skim milk powder.

University of California DavisUse DNA fingerprinting to determine which grapes

have resulted from cross pollination.Also used to introduce new varieties of grapes

Red Wine HeadacheAllergic reaction?

1% of the population could be allergic to sulfitesAlthough many sweet white wines contain more sulfites

than most red wines, yet it is still called the red wine headache.

Some this it is a reaction to tannin levels; experiments show that tannins cause the release of serotonin, a neurotransmitter. High levels of serotonin can cause headaches.

Is wine good for you? Studies have been done to show that wine

drinkers are less prone to heart disease, cancer and other diseasesThis could be a result of the antioxidant resveratrol

which may reduce cholesterol and the risk of Alzheimer’s disease.

However this antioxidant can also be found in other foods, avoiding the harmful effects of alcohol.

The study of wine is becoming so popular that you can now get a Bachelor of Science degree in oenology.

Thank You

What is used to cool the fermentation tanks during cold filtration?

Wines are aged in wooden barrelsHow are they kept air tight?How do you reduce the amount lost from soaking into

the wood? What are the differences in size of filters between the

cellulose pad filters and membrane filters?In 426 we learned about different ways of making

wine of which included distillation and crystallization processes. Where would these come into play?For removing alcohol in sparking wine?

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