Jessica Weber CBE 555 Spring 2008

Background Information Stages of production White vs. Red Reactions Role of Acids/controlling pH Quality Problems that arise Next Steps Questions

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 Categories Still Wine Production (without carbonation) Alcohol concentration is about 7-14% Sparkling Wine Production (with carbonation) Use grapes with a lower sugar level Fortified Wines (higher alcohol concentration) Alcohol concentration is about 14-30%

Wisconsin produced 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

Harvest There 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 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 O 2 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.

White When 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

White Fermentation temperature is usually about 15-18°C Sweet wine are made by leaving some residual sugar after fermentation This is done by: Harvesting later Freezing the grapes to increase the sugar concentration Killing 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

Red The fermentation process for Red wine is initially open to the air After the must is transferred to the fermentation tanks a “cap” is formed which prevents air from reaching the juice The cap is created by the solids that are pushed to the top due to the carbon dioxide production This cap is kept in contact with the juice as much as possible in an effort to retain the color and tannins This is done by punching the cap down manually or by pumping the cap over mechanically This 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. Yeast Saccharomyces 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 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 complete The aging period is not a necessary step in wine production, however it could last years if desired. Aging is most commonly done in red wines After 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 possible Temperatures are reduced to close approximately -3°C for 1-2 weeks Often 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 process This instability happens when certain proteins are present Removed 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 sediments Made from: cellulose, paper Can 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 sediments Usually 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 Storage Bottles should be stored upright for about 3 days and then at an angle or on their side in order to keep the cork wet If the cork is not kept wet it can introduce air through the tiny holes which can introduce oxidation/bacteria into the wine Also 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 sunlight As 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: C 6 H 12 O 6 + yeast 2C 2 H 4 OH + 2CO 2 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 dioxide Changes 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 ) High pH results in less flavor production in the wine To 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. Process Mechanical harvesting is usually used for less quality wines Clarification, 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 SO 2 levels are greater than 40 ppm Overly sweet wine Fermentation 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 tanks If it resulted from iron or copper a few drops of citric acid will remove the haze Filtering can also be done to remove the haze – although this will also remove some of the taste Fining can also be used to reduce the cloudiness of wine A 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 Davis Use DNA fingerprinting to determine which grapes have resulted from cross pollination. Also used to introduce new varieties of grapes Red Wine Headache Allergic reaction? 1% of the population could be allergic to sulfites Although 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 diseases This 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 barrels How 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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