i68o 



INDUSTRIES DEPENDING ON PLANT PRODUCTS 



It thus appears that, contrary to the conckisions come to by Muller 

 Thurgan and Osterwalder, the increase in the quantity of combined 

 sulphurous acid in the • must of infected grapes depends on the concentra- 

 tion of all the ingredients of the must. 



The following conclusions may be drawn from the experiments de- 

 scribed above; 



The combination of sulphur dioxide with grape mu.st depends on the 

 following factors : 



i) The proportion of sugar, which can var)" largely from that of 

 healthy grape to that infected by Botrytis cinerea, called « pourriture noble » 

 because of its enriching effect in certain wines. 



2) The proportion of glucose to fructose which is general!}^ equal 

 to I in healthy grapes, but which sometimes is less, especially in the must 

 of infected grapes; in this case the amount of combined sulphur dioxide 

 tends to diminish as the fructose is inactive. 



3) The existence of other substances than sugar in the must, and 

 the acidit3^ 



4) The physical conditions to which the must has been subjected. 



5) A rise of temperature of the must, which, if it does not exceed 

 250, hastens combination. 



II. — The influence of sulphurous acid on the fermentation 

 OF grape must. — Previous experiments had shewn that if a moderate 

 amount of sulphur dioxide is added to a must rapidly- fermenting, it com- 

 bines very quickly and without interrupting the fermentation. By repeat- 

 ed additions the relatively high proportion of i gm. per litre is reached for 

 the combined sulphur dioxide. 



A compound of aldeh^-de and sulphurous acid is produced, as Passe- 

 RiNi shewed in 1909, and the writer has studied it under the following 

 conditions; 



To begin with, he added to two portions of must about 200 and 400 

 gms. of sulphur dioxide per litre respecti^'el^^ and this combined entirely 

 with the sugar, and other ingredients of- the must. The must was then 

 mixed with pure yeast and allowed to ferment, care being taken to exclude 

 contact with the air as much as possible, and the following changes in the 

 quantity of aldehyde present were noted as the amoimt of sugar decreased : 



