Wine grape fermentation

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... 

Glucose, C6Hi206(s), (AH = —1275.2 kj/mol) is converted to ethyl alcohol, CjHsOHt/), and carbon dioxide in die fermentation of grape juice. What quantity of heat is liberated when 750.0 mL of wine containing 12.0% ethyl alcohol by volume (d = 0.789 g/cm3) is produced by the fermentation of grape juice ... 

For the color, tannin, and aroma compounds to be transferred from the skins to the fermenting wine it is necessary to mix the floating skins with the wine. This punching down the cap should be done about every 6-8 hrs with a wooden or stainless steel plunger. The less color in the grapes, the more frequently the juice and skins should be punched so there be maximum color extraction. 

For the new wine to contain the desired 15-16 vol % alcohol, it is necessary to add some sugar to the juice or the partially fermented wine except in cases of unusually high sugar content in the grapes. In any event, it is necessary to have an accurate estimate of the sugar concentration in the juice before more sugar is added and before fermentation starts. It is better not to add the calculated amount of sucrose to the juice immediately but to make two or three smaller additions after the fermentation is actively under way. This technique is known as syruped fermentation and can yield wines of as much as 17 vol % alcohol under favorable conditions of yeast nutrients and temperature control. 

Pectinolysis Saccharnmyces khiyxeri Kluyveromyces fragilis, Hansenula anomala Softening of nlives and cherries in brines, followed by formation of gas pockets in fin it. Strains of wine yeasts contain polygalacturonases which, during fermentation of grape juice, participate in the solubilization of pec tin... 

Tartaric acid occurs naturally in grapes, where it is present as the acid potassium salt. During the fermentation of grapes, tartaric acid precipitates from solution as crystals, as its solubility decreases with the increasing alcoholic concentration of the wine. Tartaric acid is also a natural component of numerous other fruits such as the currants, blackberries and cranberries. 

FIGURE 4.21 H NMR spectra (400 MHz) of time course evolution of red wine in alcoholic and malolactic fermentations for grape red must (pH 3). Peaks 1, ethanol 2, ethanol satellites 3, lactic acid 4, acetic acid 5, succinic acid 6, malic acid 7, 2,3-butanediol 8, proline 9, alanine. (From Avenoza et at, 2006.)... 

Besides water and milk, wine has been one of the oldest plant-derived drinks for humans. Generated by yeast fermentation of grape juice, it became very popular already in the Roman era (57). The global worldwide annual production of wine, with 300 million of hectoliters, represents a significant proportion of the global expanding food market. As a result of fruit extract,... 

Bisson, L. F. (1991). Influence of nitrogen on yeast and fermentation of grapes. In proceedings of the international symposium on nitrogen in grapes and wine. Am. Soc. Enol. Vitic. 323, 78-89. 

Wine produced by crushing and fermenting dried grapes produces, as in the past, well-structured red wines. They are typically characterized by high residual sugar contents and, in the Veneto region, they are termed Recioto wine. 

This newly fermented wine is cloudy from suspended materials such as yeast, protein, colloids, and fine grape cellular solids. In storage, a natural clarification, or gravity settling out, of these materials takes place. 

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