f)58 EXPERIMENT STATION RECORD. 



FERMENTATION— BACTERIOLOGY. 



Fermentation, V. T. Bioletti {Ckilifornia yHta. Rpt. Viticult. WorJc, 

 lSS7-9o pp. 37!)-421, Jigs. 6). — The author reviews the geueral prin- 

 ciples of fermeutation and discusses the subject from an historical 

 standpoint. Notes are given on the origin of yeasts, conditions of 

 fermentation, purilication and selection of yeasts, acidity, nitrogen, 

 at'Tation, influence of temperature, and refrigerators or cooling machines. 



Experiments were made with pure and selected yeasts as well as with 

 other fungi, particularly Botrytis cinerea, which is reported upon at 

 length ill another place (p. 959). The principal yeast experimented with 

 was Johannisberg. These experiments were supplemented with yeasts 

 from various other sources. In general there seems to be no indication 

 of the production of a greater amount of alcohol by the use of pure 

 ferments. In fact, some of the wines seem to contain less alcohol than 

 those fermented by the ordinary methods of production. However, 

 owing to the difficulties in obtaining exact data the author considers 

 that it would be unwise to draw conclusions without a number of fur- 

 ther trials. In every experiment conducted at Berkeley the wines fer- 

 mented with the addition of yeasts from cultures were cleaner and 

 fresher tasting than those allowed to ferment with whatever yeasts 

 happened to exist on the grapes. The difference, while sometimes 

 slight at first, increased with the age of the wine. The promptness 

 with which fermentation begins and the short time in which it is fin- 

 ished when yeasts are introduced prevents the development of any 

 large number of injurious ferments, and the rapid clearing makes it 

 possible to rack the wine early and thus remove from it the influence of 

 many other injurious microorganisms. 



A summary of conclusions is given which shows the merits of pure 

 yeasts in that they produce a quicker fermentation, a more prompt 

 clearing, a cleaner taste due to the overslaughing of injurious ferments, 

 and probably an improvement in flavor and bouquet. According to the 

 author, the indications are that the use of a pure California yeast would 

 be preferable to any other. This subject is to be further investigated. 



Fermentation at high temperatures with the addition of various sub- 

 stances was investigated to some extent. Defective fermentation in a 

 hot climate is well known, and various substances are added to wine to 

 render the must unsuitable for the growth of injurious organisms, to 

 increase the development of the yeast by making must more favorable 

 for its growth, and to keep the temperature of the must below tlie 

 optimum for injurious ferments. The substances most used for this 

 purpose are gypsum, tartaric acid, unripe grapes, ammonium phosphate, 

 peptone, sulphurous acid, sulphites, and asaprol. Theeftect of each of 

 these substances on fermentation and upon the quality of the wine is 

 given. 



A brief account is given of inconclusive experiments made with a 

 patented apparatus for use in closed fermentations. 



