CAPE WINE-LEVURES. 22J 



as will be seen later on — it will he easily understood 

 that an adequate addition of pure levures to the fresh 

 must is of necessity most useful. The addition of a 

 large quantity of pure levures to the fresh must enables the 

 particular levure to multiply itself to such an extent as to sup- 

 press the other micro-organisms effectively by its vastly superior 

 numbers. So that, although the must is not sterilised, it is still 

 possible for the pure levures to bring out their characteristic 

 properties in the product of fermentation, namely, the wine. 



The main advantages gained by conducting a fermentation 

 with pure levures are: 



i i ) An almost immediate fermentation whereby the dops 

 and must are prevented from getting sour before the vinous 

 fermentation starts. 



( 2 ) A regular fermentation until either all the sugar has 

 disappeared or so much alcohol has been formed (16-17 volume 

 per cent.), that it prevents any further fermentation. This is 

 one of the main points in favour of using pure levures. 



(3) A firm depot of lees, the wine thus getting bright fairly 

 soon. 



(4) A clean taste, which is very important. 



(5) A slight influence on the bouquet of the wine, although 

 this must not be exaggerated. In order to sell their pure 

 levures, say. from Johannisberg or the Champagne district or 

 Sauternes, some unscrupulous people maintain on their adver- 

 tisements that it is possible to make, say, a Sauternes wine out 

 of any ordinary must by using their Sauternes levures. This, 

 of course, is nonsense. It is, to say the least of it, a gross 

 exaggeration of the truth. 



(6) Must fermenting with good pure levures can go up to 

 such high temperatures as 38 to 40 C. without running much 

 risk of being subjected to mannitic fermentation, for the simple 

 reason that the levures have all along been so active and pre- 

 dominant that the mannitic bacteria had no chance of developing, 

 and are consequently practically wanting in such a must. The 

 results obtained with my pure levures during several vintages 

 go to prove the accuracy of the above. 



It may be here pointed out that, if the temperature goes up 

 to 38-40 C. in a spontaneous vinous fermentation, a mannitic 

 fermentation easily sets in, since the levures usually have to 

 struggle for existence at such a high temperature, whereas the 

 mannitic bacteria find no difficulty in propagating themselves 

 under these circumstances. Since the mannitic bacteria form 

 mannite out of the sugar of the must together with certain un- 

 pleasant volatile acids, a wine that has suffered from a mannitic 

 fermentation remains sweetish-sour (aigre-doux) and has an 

 unpleasant taste characteristic of the disease. Since the sweet- 

 ness is here due to mannite. it cannot be made to disappear by 



