112 Journal of AgriciiUiiJC. Victoria. [lo Feb., 1911. 



Nevertheless, because the sanguine hopes of twenty years ago were 

 not fully realized we must not lose sight of the real gain which undoubtedly 

 occurs in this direction. Some yeasts, at least, have proved themselves 

 capable of bringing about an improvement in the bouquet of the wines, 

 fermented by them. 



The advantages to be gained from the use of pure veasts are summed 

 up by Professor Astruc as follows: — * 



1. More rapid, more complete, more re^'ular fermentations and a belter yield 

 in alcohol. 



2. Wines of better general quality, sometimes clearing earlier and possessing 

 more bouquet; ahvavs easier to preserve, poorer in dangerous germs, and clean in 

 taste. 



Problems Still to be Solved. 



These are numerous and some are important. As regards bouquet, its 

 frequently fugitive nature has led to an ingenious explanation which sup- 

 poses the existence in the must of certain glucosides or allied substances 

 whicli give rise, under the influenc of a certain ferment, to a bouquet, 

 whereas under the agency of a different ferment this bouquet would not 

 be evolved. According to M. Astruc — 



It seems as though there were transformation by the yeast of a natural odoriferous 

 element of the must. The Cabernet flavour would transform itself thus by fermen- 

 tation into the special perfume of Bordeaux, and that of Pinot into the Burgundy 

 perfume; but let us reverse matters, let us place the Burgundy yeast in the Cabernet 

 must and vice versa, and the results as far as bouquet is concerned become uncertain, 

 being temporary or permanent, good or bad, accordmg to the race of yeast employed, 

 or the accidental composition of the must. ... Is this natural constituent, 

 which has been recognised as depending on the soil and the variety of vine, a special 

 glucoside, or else is this only a convenient way of concealing our present ignorance on 

 the subject? .... The only point which seems to me to be solved for one 

 particular spot is that the nature of the bouquet depends on the variety of vine, whilst 

 its intensity seems to depend particularly on the yeast, and that such bouquets are 

 often fugitive or slow in showing themselves when they do make their appearance. 



He further points out that, in the quest after bouquet, other risks may be 

 run. " Beware of bouquet-producing levures ; they are often ' exigeantes,' 

 lazy, or inferior from other standpoints." 



A pertinent question was asked some years back by Duclaux — Is the 

 bouquet of wine due to one ferment alone or to co-operation of several ? 

 In Nature a whole group of yeasts does the work. This is quite different 

 to what happens with a pure yeast, which, if it fulfils expectations formed 

 when it w-as added, is responsible for transformation from start to finish. 



It is well known that, in many spontaneous fermentations, the lemon- 

 shaped yeast known as .S. Aficulatus, so abundant at the commencement, 

 gives place entirely, later on, to the true wine yeast ►S. Ellifsoideus. 



The former possesses only poor fermental power, ceasing to act as soon 

 as a moderate alcoholic strength is reached ; yet, in some quarters at least, 

 it is held responsible for the production of aromatic substances which pos- 

 sibly contribute to the special bouquet of certain wines. Numerous different 

 varieties of yeasts exist, and it is by no means improbable that in some, at 

 least, of the celebrated wines of the world, it is to the co-operation of 

 several and not to the development of one yeast alone, that are due the 

 qualities which have rendered these wines famous. 



The.se few examples will suffice to show the complexity of the question 

 and the need which exists for further experimental work before the theory 



* Henri Astruc — L'Etat actuel de la Question des Levuers en (Enologie. Report to the Soci^tf des 

 Aericulteurs de France, May, 1908. 



