The natural enzymes found in grapes control many chemical processes. To supplement or support the grape's own enzymes, oenological enzyme preparations have long been produced and used in winemaking to improve juice yield, release aromatic substances, improve colour extraction, extract softer tannins, improve filtering properties and release mannoproteins from the yeast. The addition of the corresponding preparations takes place in the stages of pressing, mash fermentation, fermentation, malolactic fermentation, clarification, ageing and filtration. Enzymes or enzyme groups authorised within the EU are glucanases, lysozyme, pectinases and ureases. See also under oenological tannins.