This pure calcium sulphate occurs naturally in the typical chalk soil of Albariza in the Spanish DO area of Jerez, but also in some other Spanish areas. However, it is also produced industrially. In the traditional process, which has been used since ancient times, Yeso is added to the grapes before they are pressed (about 1 kg Yeso per 700 kg grapes). This strengthens the acid structure through the formation of tartaric acid, produces aromatic esters and promotes the formation of flor (special type of yeast), which covers the wine in a thick and wrinkled layer after a few weeks. This protects it from oxidation and gives it its unmistakable sherry tone.
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Diplom-Sommelier, Weinakademiker und Weinberater, Volders (Österreich)