Labo VinCorrecting the juice
Juices of numerous fruits are not balanced enough to give the perfect wine we wish. Deficiencies or excesses have to be corrected.
- The acidity must be corrected in order to obtain an ideal acidity, variable depending on the desired type of wine. That means it is necessary to measure beforehand the sap acidity.
- The sugar content also has to be evaluated and eventually corrected so as to obtain a wine with the alcoholic degree and residual sugar needed (dry, medium dry, sweet...). The choice of yeast strain will also define the sugar content in the finished wine.
- A lot of juices do not contain enough nutritive salts so as to ensure a good health to the yeast and thus a good fermentation. An addition will be often necessary.
- Some saps do not contain enough tannin [ The word tannin applies to various badly defined compounds, often polyphenolic acids esterified by a sugar. The tannins are very widespread in a lot of plants, mostly barks, fruits, tree leaves, oak wood...
The oenological trade tannin is mostly extracted from oak apple, sometimes also from grape skin.
The tannin has a typical astringent savour and a characteristic subtle odour. It is an amorphous pale yellow to brown powder. The tannin is essential in a wine: it is necessary for the wine clarification (min. 3 g/10 L juice). It forms insoluble compounds with proteins and metallic ions, starch and a lot of alcaloids. It also contributes much to the wine keeping. The tannin content of wines varies from 350 mg/L in white wines up to more than de 3 g/L in red wines. Ageing wines in oak casks increases their tannin content. ] . This correction will be carried out on the finished wine, but if there is not enough tannin, a straight off addition of 3 g/10 L will ensure a good clarification. - Most often pectinase [ The pectinase is an enzyme (protein, biological catalyst) that destroys the pectin. It follows a better flavours extraction, a better sap yield, along with a good ulterior clarification. The pectinase is sold as a liquid or a powder. Conform to the manufacturers instructions. Too much pectinase is not damaging, but it is wasting. ] will be added at first, in order to destroy the pectin [ Mixture of methylated polygalacturonic acids. By enzymatic hydrolysis, the pectin releases toxic methanol. It forms a net that traps the juice, rendering it viscous, so decreasing the yield at the pressing stage. ] contained in a lot of fruits, otherwise the wine will not clarify or with difficulty.