clusters are generally shaken then trampled. The practice of moderate trampling allows the grains to burst, releasing the juice and pulp (it cannot be used for white wine from black grapes as the premature bursting of the berries would cause a coloured must). The practice of shaking or stalking has the advantage of separating the stems from the cluster of grapes and avoids giving the wine a herbaceous taste at pressing. The skin is not macerated and the transparent yellow colour is retained. The winemaker can soak the skins of white grapes and practice maceration if the quality of the grapes is good. Pre-fermentation Maceration is generally performed at a controlled temperature to delay the onset of fermentation. This technique improves the extraction of varietal aromas and their precursors which are mainly located in the skin. Acidity decreases as does the ratio of Colloids (large pectin type molecules) and aging potential. To be implemented, this process requires a perfect de-stalking, moderate crushing and sulphite to protect the wort from oxidation. The duration (typically 5 to 18 hours at 18 °C) depends on the variety, the temperature of maceration, the maturity of the grape, and the quality of the soil. The trampled and de-stemmed harvest is then pressed. The type of wine press also affects the potential quality of the wine. Since the 1980s, pneumatic presses have improved the work involved by working in airtight conditions and allowing a fine control of the pressure to extract the juice without damaging the grapes. The juice or moût de goutte (Must of Drops) is the juice that flows naturally from the berries crushed under their own weight prior to pressing (on the way to the press). Trampling increases its proportion and makes the material profitable by processing a higher tonnage of grapes in the same time. The moût de presse (Must of the Press) is the juice flowing from the press from the pressure on the grapes. It concentrates the qualities or the defects of the grape: it is rich in aromas, colloids, or phenolic compounds. However, it can also be marked by olfactory defects, such as the smell of fungus on spoiled grapes or the vegetable smell of a harvest with insufficient maturity. The blending or not of the moût de goutte and the moût de presse musts and release depends on the health of the grapes, the method of pressing, and