Biochemistry of Natural Wine Making

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 able to contribute greatly to the improvement of wine quality. Wine making, or vinification, is the production of wine, starting with selection of the grapes or other produce and ending with bottling the finished wine. Although most wine is made from grapes, it may also be made from other fruit or non-toxic plant material. The basic fermentation process whereby alcohol is produced from the sugar in grapes is very simple, but its chemistry is still not completely understood. As this knowledge increases, winemakers are being helped to improve the quality of their wine. The composition of grapes is of great importance in determining the quality of the wine produced. Many compounds are carried over from the grape juice into the wine, and other compounds undergo reactions to form the compounds distinctive to wine. It was once common to ameliorate the wine produced with a variety of chemical treatments, but now this is frowned upon. In this new climate, using high quality grapes is essential to producing high quality wines, and grape composition is more important that ever. In general, grapes consist of clear juice (80%), skins (8%), seeds (4.5%), pulp (4.5%) and stems (3%). The skins, seeds, pulp and stems are