not require the use of the press. The remaining 30-40% that comes from pressing can have higher pH levels, lower titratable acidity, potentially higher volatile acidity and higher phenolics than the free-run juice depending on the amount of pressure and tearing of the skins and will produce more astringent, bitter wine. Winemakers often keep their free-run juice and pressed wine separate (and perhaps even further isolate the wine produced by different pressure levels/stages of pressing) during much of the winemaking process to either bottle separately or later blend portions of each to make a more complete, balanced wine. In practice the volume of many wines are made from 85-90% of free run juice and 10-15% pressed juice. Types of press There are many different types of wine press, but they can be broadly divided into continuous presses and tank presses. Modern winemaking tends to favour tank presses with pneumatic membranes, which squeeze the grapes more gently than continuous presses. The press wine is often kept separate from the free-run, and kept for later blending or disposing. press can also be dependent on climate and slothrating. Malolactic fermentation A second microbiological transformation commonly takes place after the alcoholic fermentation of red wines. This is usually referred to as the malolactic fermentation (MLF), in which malic acid, naturally present in grape juice, is converted into lactic acid under the influence of bacteria (it is not strictly a fermentation). MLF is almost universally practised for red wines. It often occurs naturally, owing to the presence of lactic acid bacteria in wineries, but there are also commercially available preparations of bacteria to inoculate for MLF if necessary. Racking Once the MLF is complete, the red wine is usually racked (decanted) off its lees (dead yeast cells and other solids), and has sulfur dioxide preservative added to avoid oxidation and bacterial spoilage. Aging Most red wine is aged for some period before bottling, though this can vary from a few days, in the case of Beaujolais Nouveau to 18 months or more in the case of top Bordeaux reds. Aging can take place in stainless-steel or concrete tanks, or in small or large oak barrels. The latter impart some flavour to the wine as a function of their age and size (small, new barrels give more flavour than large, older barrels). Fining and stabilization Red wines sometimes undergo fining, which is designed to clarify the