Biochemistry of Natural Wine Making

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Wine is of great importance in our society today, and has been so for thousands of years. Grapes have been cultivated for wine production in the Near East since 4000BC, and in Egypt since 2500BC. They were spread from the Black Sea to Spain by the Greek Empire,into Germany by the Romans and to the New World by Columbus. Wine has had religious significance as both an offering and a sacrament since Biblical times, and this has helped its development. Today an enormous variety of wines are available, made from more than 5000 varieties of a single species of grape: Vitis vinifera. In the production of all these wines, chemistry is important, and as some of the complexities of wine chemistry have begun to be understood chemists have been…show more content…
There are six main classes of phenolics found in grapes: catechins, procyanidins, anthocyanins, flavonols, hydroxycinnamates and hydroxybenzoates. The difference between red and white wines is due to the different types of phenolics in the two beverages. The simple phenolics - the hydroxycinnamates and hydroxybenzoates - occur in the flesh of the berry and so occur in both red and white wines. The other more complex phenolics, known collectively as flavanoids, occur in the skin, seeds and stems and so occur mostly in red wines. The procyanidins are also known as condensed (or non-hydrolysable) tannins, and it is these that give wine most of its astringency. A further group of tannins, the hydrolysable tannins, are found in wine that has spent time in oak barrels. These tannins are also astringent, and are complex esters of glucose and gallic acid. Anthocyanins are the commonest source of colour not only in grapes but in all flowering plants. Their color depends on the number of hydroxyl groups on the molecule and can range from orange through red to purple. The fourth major constituent are aroma compounds. The basic flavor of a wine is formed from the balance of sugars, acids, phenolics, and ethanol, but the character of the wine is provided by the volatile aroma compounds. Over 1000 of these volatiles have been identified in wines from around the world, all present at low, almost trace, levels. The most important volatiles in the grape
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