Harvest (wine) of wine, winemakers would use the sugar and acid levels of the grape as a guide in determining ripeness. Early winemakers tasted the grapes to gauge ripeness. Modern winemakers use a refractometer to measure high sugar levels and °Brix or titration tests (using an indicator such as phenolphthalein) to determine the titratable acidity within the grape. In recent times there has been more of an emphasis on the "physiological" ripeness of the grape, usually in the form of tannins and other phenolics. Currently, tasting is the only way to measure tannin ripeness, which can take experience and skill to do
History of the wine press would subject the grapes/pomace to increasing pressure from one end of the press to the other with new grapes being added and the pomace being continuously removed. Another advancement in the horizontal batch press was the complete enclosure of the press (sometimes called "tank press") that reduced the exposure of the grape must to air. Some advance presses can even be flushed with nitrogen to create a complete anaerobic environment that can be desired for wine making with white wine grapes. Additionally, many of today's modern presses are computerized which allows the operator to control exactly how much pressure is