3-— ON FERMENTS CAUSING " CASSE "' IN WINES. 



By Raymond Dubois, Diplome E.A.M., B.Sc, F.C.S., F.S.C.I. 

 (Victoria), Government Viticultural Exi->ert. 



INTRODUCTION. 



Since the grafting of our wine varieties on American Phylloxer*- 

 resistant stocks, wines seem often to suffer from a disease which 

 presents the following characteristics. 



Wines which are bright in colour and seem perfectly sound 

 suddenly modify their colour when exposed to the air. They become 

 brown and turbid, their cloudy appearance rendering them unfit for 

 sale. 



If the wine is contained in a glass jar, where it can be observed, 

 it will be noticed that the discolouration starts from the surface 

 exposed to the air in the form of a thin vale of colouring matter and 

 little by little .sinks in the liquid forming a brown-black precipitate, 

 which adheres to the sides of the jar. In a few days the wine com- 

 pletely loses its original colour, assuming a very characteristic straw 

 colour. 



Racking or decanting seems to increase the decomposition in- 

 stead of checking it, as is the case with other wine diseases. This 

 disease, known among French wine-makers under the name of 

 " casse "—Break — on account of the sudden break in the colour, 

 ma\ be frequently noticed in both red and white wines made from 

 over-ripe grapes. So common has it become that it has been the 

 subject of numerous studies by several distinguished oenochemists, 

 as may be seen from the appended bibliography. 



Most of the authors who studied this disease found in the affected 

 wines blackish matter, partly in solution, which, according to them, 

 would be the cause of the alteration in the colour. They attribute 

 to this matter, acting as an oxydase, the property of fixing the oxygen 

 on the various constituents of the wine, of oxydising it, if we may use 

 such an expression, this oxydisation causing the break in the colour. 



The present studies were undertaken with the object of ascertain- 

 ing how the black matter was formed in the wine, its composition and 

 mode of action, and the way of checking its formation. 



Five litres of affected wine were concentrated by evaporation 

 at 60° C. The residuum treated with water and brought to boil- 

 ing point was left to cool down. During the process of cooling down 

 an abundant cloud of blackish matter precipitated at the bottom of 

 the vessel. It was found to be composed mainly of albuminoid and 

 pectic matters. This precipitate placed on a filter was washed 



