The Claripcatiou and Limpidity of White Wines. 737 



In addition to the two natural influences which have been con- 

 sidered, there is an artificial action which can now be easily employed 

 to hasten the clarification of white wine, viz., the action of heat 

 applied by pasteurisation. The fact that certain matters are 

 coagulated by heat is well known, and it is even known that the 

 presence of alcohol assists this action. Thus wines heated to a 

 temperature even lower than that usual in pasteurisation become 

 more or less cloudy, according to their age and previous methods of 

 clarification employed. 



With complete rest at the end of a more or less lengthy period 

 this cloud becomes more concrete in the form of a light flaky deposit 

 which can only be successfully eliminated by a light fining or 

 filtration. 



It is for this reason that pasteurisation of white wines is less 

 common than that of red wines. In addition to the action of heat, 

 that of cold can be considered, but it can hardly be applied success- 

 fully by natural means. Cold has generally less influence upon the 

 clarification of white wines than red wines, although it is by no means 

 negligible. The activity of organisms living in the wine, yeast or 

 microbes, becoming diminished, if not completely arrested, these 

 organisms are more easily deposited. Then the organic matters fall 

 more quickly, besides the precipitation of all matters in suspension is 

 hastened by the formation of the deposit of cream of tartar crystals. 



III. 



The preceding considerations apply to wines of which the 

 evolution is normal, but there are many circumstances where this 

 evolution is altered by .diverse causes which more or less affect the 

 natural clarification of the liquid. 



Cloud Caused by the Action of Microbes. 



It sometimes happens that, instead of diminishing, the opalescent 

 cloud in young wines increases until it almost returns to its original 

 milky appearance. Shaken up in a glass, silky threads are visible, 

 and the microscope shows" the presence of a large quantity of bacteria, 

 more or less closely joined together, which are the microbes of 

 " tourne" (turn). 



This state of the wine is most frequently seen when the condition 

 of the grapes has been rendered defective by diverse causes such as 

 hail, insects, fungoid diseases, or else when the fixed acidity is 

 insufl&cient. 



Thus wines of inferior quality, such as pressings, which are (*) 

 always more watery than wines run from the vat, are particularly 

 liable to this microbian invasion, and consequently are more difficult 

 to handle and mature. Not only must this microbian action be pre- 

 vented as soon as possible to have the wine clear, but also to prevent 

 the efl:ects of this action upon the flavour of the wine. This is not 



(*) In France (Trans). 



