Sugar wine grapes

Wine. The earliest known wines were made in Iran about 5400—5000 BC (25). The species of grape used is unknown and may have been either the wild grape Fitis viniferus sylvestris or a cultivated precursor of the modem wine grape V. viniferus viniferus. The source of the yeast used, and the procedures used are completely unknown. In modem times, grapes (about 21—23% sugar) are pressed the liquid must is either separated and allowed to settle for 1—2 days (for white wines) before inoculation with yeast, or the whole mass is dkectly inoculated with yeast (for red wines). In either case, while the initial fermentation takes place, the carbon dioxide formed by fermentation excludes ak and prevents oxidation. White wines are transferred to a second fermentor (racked) near the end of fermentation and kept isolated from the ak while solids, including yeast, settle out, a process that requkes about six... 

Native American grapes (5) contain less sugar than Vitis vinifera varieties. A publication on California wine grapes (6) revealed that the average Balling of must from the recommended wine varieties for California ranged from 20° to 25° with a few exceptions above and below these limits. 

The quick or competitive procedure for making sweet table wines depends on sweetening a dry table wine with a very sweet blending wine or with sugar or grape concentrate and some procedure of sterilization which ensures that no viable yeast cells are present in the closed bottle. The simplest is pasteurization of the blend after it has been bottled. This technique, however, is not favored as it tends to give the wine a cooked aroma and taste. 

Y Shimazu, M Uehara, M Watanabe. Simultaneous determination of ethyl alcohol, polyols, and sugars in grape must and wine by high-performance liquid chromatography. J Brew Soc Japan 75(4) 327-331, 1980. 

Fermentation of the sugar from grapes yields the ethyl alcohol in wine. 

Once the grapes arrive at the winery, a sample of the juice is assessed chemically for parameters such as probable alcohol and sugar content. Grapes must have fall within the range of 12-14 Baurne. Wines can be made separately by variety or mixed together. 

Properties.—Succinic acid has been known for a long time. It is quite widely distributed in nature. It is found in unripe fruits, especially in grapes, also in lignite, in peat and in many plants. Its most important occurrence is in amber from which it may be obtained by distillation. It is also a constituent of wines where it is the product of the alcoholic fermentation of the sugars of grape juice. Another source, which will be considered later, is from malic and tartaric acids by bacterial or mould fermentation. Succinic acid crystallizes in plates or columns which melt at 182°. It sublimes when it is heated below its melting point. When heated rapidly to 235° it loses water and forms an anhydride. It is soluble in 14 parts of water. 

Fermentation Yeast can spontaneously ferment the sugar in grapes or apples and form ethanol. When the process occurs in grapes, it results in wine. In apples, it produces a beverage called hard cider. The first stage in the fermentation process is exothermic, and the balanced equation for the reaction is as follows. 

Fermentation affects the sugars in grape juice, but the proteins remain in suspension with the result that the wine appears cloudy. To clear the wine, a fine claylike substance called Bentonite can be added. Bentonite attracts positively charged particles and precipitates them. This process is called fining. 

Wine based on the fermentation of sugars from grapes as well as other fmits, rice, and leaves. Table wines range up to around 14% ethanol by volume dessert or aperitif wines, usually sweeter, range from around 14 to 24% ethanol. 

The source of sugar varies. Grape juice is used to make wine, using natural yeasts on grape skins. Allowing fermentation to stop naturally produces a dry wine, with low sugar content. Stopping fermentation... 

Figure 9.13 To the winemaker, yeast is integral to crafting wonderful, complex wines from simple, sugar-rich grape juice. Grape juice is converted into wine by the action of wine yeasL Some wine components are whoUy generated by yeast as part of metaboUsm whilst others are essentially as created by the grapevine. The large number of compounds synthesised or modified by wine yeast have a major impact on wine quality and style. Commercial yeast strains possess different abilities to form and modulate compounds that impact on wine sensory properties. These compounds are produced as a result of yeast metabohe processes.

Grape Liquors. In addition to wine, grapes can be used to produce a variety of other liquors. Champagne and sparkling wine are made either by injecting carbon dioxide into already-fermented wine or by adding more yeast and sugar to the wine to induce a second fermentation process. With the latter method, the wine is then capped in a special container that traps the carbon dioxide that is released as a by-product of fermentation. 

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