Alcoholic Fermentation Grape Wine example essay topic

Introduction The homemade production of wine is a fun and challenging hobby that many people can enjoy. In this paper the reader will be taken through several different steps and processes that must be accomplished for your wine to be of satisfactory flavor and clarity. Crushing and stemming This first step may be performed by hand or by machine. For handling a ton or more of grapes, use a mechanical crusher-st emmer. Using a small crusher-st emmer, two persons can crush and stem a ton of grapes in about one hour.

To collect the crushed grapes, which are also called the must, the machine is placed and supported above a container. A large polyethylene plastic tub or garbage can is sufficient. The important objective is to minimize bitterness by thoroughly crushing the berries without macerating the seeds, and while recovering all of the skins and juice in the must. After stemming and crushing, the ferment ors are filled with the must to about two-thirds capacity, to avoid foaming-over during fermentation. After all of the must has been poured into the ferment ors and the sulfur dioxide has been added, the ferment ors should be covered with cheesecloth or plastic to keep out insects. Temperature, total soluble solids, tit ratable acidity, and the free and total SO 2 of the must in each ferment or should be determined and the results recorded.

Adding sulfur dioxide Sulfur dioxide (SO 2) is a chemical compound that has been used in wine making for more than a century. Because it is known that wine yeast produce small amounts of SO 2 during fermentation, SO 2 can be considered a natural constituent of wine. Judicious and moderate use of SO 2 has long been recommended. Recent research shows that the best quality wines are made when SO 2 has been used both before and after fermentation.

For grapes free of mildew, rot, or mold, usually from 50 to 100 parts per million (ppm) is used or about 75 ppm is adequate. This mild antiseptic is commonly used in the form of potassium (K 2 S 2 O 5), and is available from home wine making suppliers. To obtain 75 ppm of SO 2, add 1/4 ounce to each 10 gallons of juice or must. For grapes that have appreciable amounts of moldiness, rot, or broken berries, use twice this amount of SO 2.

To add SO 2, dissolve the in a small portion of the juice; then add this back to the bulk of the must to be treated and mixed thoroughly. Allow this mixture to stand about 2 hours before adding the wine yeast starter culture. Alcoholic fermentation Grape wine is the alcoholic product of the fermentation of grape juice. The essential feature of this fermentation is the conversion of the grape sugars, glucose and fructose, to ethyl alcohol (ethanol), carbon dioxide (released as gas), and flavor components. This complex process is accomplished by living yeast cells. The alcohol produced through fermentation is a wine's major flavor component.

It also affects the solubility of many wine constituents. Some is used in forming other flavor compounds. It also enhances wine's resistance to spoilage. Wines traditionally are classified according to their alcoholic content. Fermentation in wine making is not only fascinating but it is critical to success. Typically, there are three distinct stages.

1. A resting period of 12 to 24 hours, during which yeast cells grow and increase in sufficient numbers to commence the fermentation. 2. Vigorous activity of 2 to 3 days, during which the yeast rapidly ferments one-half to two-thirds of the sugar to alcohol and carbon dioxide gas-the latter development is accompanied by frothing-and the skins rise to the surface, become compact, and form the "cap". 3. A more or less quiet stage of relatively slow fermentation for 3 to 4 days after pressing the partially fermented juice off the skins.

Pressing Basket presses are available in various sizes, either hand-operated, motor driven, or hydraulic driven. The basket press, probably the most expensive piece of equipment needed in home wine making, is also one of the most worthwhile investments. A properly cared for press should provide a lifetime of trouble-free service. Fill the basket with partially fermented must and allow the liquid portion to flow freely into a stainless steel bucket or polyethylene plastic pail covered with plastic window screen to catch solids.

Discard solids from the screen surface as needed. This portion of the partially fermented juice or wine is called the "free-run". After all of it has been collected, apply pressure slowly and not for too long a time. Too rapid application of pressure causes the wet solids to squirt through the basket openings, which defeats the basket operation. As pressing proceeds, the free-run and / or the press wine should be placed into narrow-necked glass containers or clean oak barrels to about 90 percent of capacity, for fermentation to complete. Racking Racking or siphoning, a simple and convenient technique for clarifying wine, should be done carefully, so that the wine will obtain a degree of clarity satisfactory to most winemakers as well as to the wine consumers.

By siphoning or racking, clear wine can be separated from the sediment in one container and transferred to another clean container. New wine racked off the gross fermentation lees is usually transferred into a clean oak barrel for aging. It may also be transferred into a clean glass carboy, jug, or other suitable container. Because the SO 2 initially added is exhausted during fermentation, it should be added again at this time (about 50 to 75 ppm).

Aging and topping Most red wines benefit from aging in oak barrels. In addition to the many slow reactions that occur during aging, wood extractive's contribute to the wine's overall flavor complexity. Naturally, care should be taken to avoid excessive woodiness by controlling the wood aging time. New barrels will impart more wood flavor much faster than will older, used barrels. Thus, special care should be exercised when aging wine in new barrels.

Wine in new oak barrels should be tasted every 1 to 2 weeks and, once it has attained the desired degree of oak character, as determined by taste, it should be transferred to an older, used barrel for further aging or storage if desired. If no further aging seems necessary, it should be transferred to glass storage containers or bottles. Bottling The wine is "ready" for bottling after the desired degree of wood aging has been attained, as determined by taste. It should also be assessed as free of apparent or preventable defects or instabilities within quality standards acceptable to each winemaker, by examination for desired clarity, smell, and taste.

Check the free and total SO 2. It is customary to adjust the free SO 2 as needed to about 25 to 30 ppm at bottling. This helps to prevent oxidation of the wine after bottling due to dissolved oxygen that may be picked up during bottling. When selecting bottling devices, it is highly desirable to minimize aeration, which in turn will minimize oxidation of the wine after bottling.

This is best achieved using devices that provide for gravity flow of the wine and fill the bottles from the bottom of the storage container. Such bottling devices are often referred to as "gravity bottom filling". New wine bottles should be rinsed in hot water to remove dust particles and air dried before use. Conclusion Hopefully after reading this paper, the reader has obtained more insight in creating a homemade wine that everyone can enjoy.

The process may seem lengthy, but time is normally essential in the completion of many things. And if your first batch does not come out correct, do not get discouraged. Try again until things get better. Before you know it, you will be able to consider yourself a wine connoisseur.