I34S IXDLSTRIES DEPEXDIXG OX PLAXT PKODUCTS 



temperatures, the alcoholic fermentation of the musts may be either dis- 

 astrously shortened or dangerously prolonged as the case may be. 



The Question of Musts. — In normal years, the methods of control 

 usually employed in Tunisian wine cellars to obviate an excessive rise of 

 temperature in the vats give satisfactory results, if care is taken to work on 

 normal musts properly corrected with regard to the due proportions of 

 their elements, especially in respect to acidity and saccharine content. The 

 usual means of prevention consist in : 



i) Cooling the grapes as a prior precaution during the night, leav- 

 ing them outside in pans or boxes, after sometimes sprinkling them with 

 water ; 2) using small vats, in which the losses of heat by radiation are pro- 

 portionall}^ larger than in the large ones ; 3) raising of the must, with or 

 without aeration ; 4) drawing off must, that is to say racking, as soon as 

 the temperature in the vats reaches the dangerous point (35-370C) ; 5) using 

 nietallic vats in order to increase the loss of heat by radiation ; 6) using 

 cooling agents ; unfortunately the water for feeding these cooling agents is 

 insufficient and lukewarm ; 7) using antiseptics, the mutage being effected 

 with sulphyrous anhydride, on condition that not more than 450 mmg. of 

 sulphurous acid per litre (of which 100 mmg. in the free state) remains in 

 the wine ; 8) using local yeasts acclimatised to sulphurous anh3^dride ; 

 9) utilising several of the above mentioned methods of prevention together. 



In hot years, as for instance 1913, these methods are often impotent to 

 moderate the irregular course of fermentation. The following two examples 

 are given : i) the first relates to a highly concentrated must, as it shows 

 an initial densit3^of 1093 (or 218 grms. of sugar per litre). The first slight sul- 

 phuring is carried out (7.5 grms. of sulphurous acid per hectolitre) and fer- 

 mentation starts pretty rapidly, being activated by the raising of the must 

 ("remontage"). As early as the third day, dangerous temperatures are reach- 

 ed, and on the fourth the temperature is 37° C. The cooling is then done by 

 a refrigerator, which brings it down to 34*^ C. and then, after another rise, the 

 must is racked off at 33.5° C. 7 days were required to effect attenuation 

 which was quite inadequate because racking is effected at 1013 (instead of 

 0.995-0. Q97 which a normal fermentation of 4 days should produce) 2) The 

 second example, on the contrary, presents the case of a highly accelerated fer- 

 mentation. After sulphuring with 15 grms. of sulphurous acid per hecto- 

 litre, the temperature reaches 35° C. in 12 hours. The first refrigeration en- 

 tails a gain of two degrees only, then the temperature goes up again to 35° C. 

 and a second refrigeration is effected. Racking is carried out after barely 

 4 days of fermentation, with an almost normal reduction. 



Possible Solutions. — It results from these facts that the means custom- 

 arily used to prevent abnormal rises of temperature in the fermenting vats 

 are powerless in hot years to ensure satisfactory cooling. Consequently the 

 possible solutions are considered, and are brought under two general me- 

 thods : .4) wine making is conducted during the hot season, the effect of 

 cooling being increased by resort to artificial cold; 7?) or the principal fer- 

 mentation should be left over for a temperate period (autumn or winter). 



