PRESSURE 111 



Pressure 



The investigations of Regnard l and Melsens 2 have shown that 

 the yeasts are able to resist a very strong pressure. Regnard submitted 

 a yeast to a pressure of 1000 atmospheres for 1 hour without killing- 

 it. Melsens has used pressures of 8000 atmospheres and noticed no 

 diminution in the vitality of the yeasts so treated. Kite, Giddings 

 and Weakley 3 in studying the effects of high pressures on micro- 

 organisms used a number of common yeasts. Samples of grape 

 sugar in water which were inoculated with baker's (Fleischman's) 

 yeast did not ferment after being subjected to 60,000 pounds pres- 

 sure per square inch for a half hour at room temperature. With 

 Saccharomyces cerevisiae, Meyer, there was no growth after 80,000 

 pounds pressure. While the results are not concordant, it may be 

 seen that this yeast could stand pressures of between 50,000 and 

 55,000 Ibs. pressure for 10 or 20 minutes, in distilled water. In 3 per 

 cent cane sugar solution, there was one instance where this yeast re- 

 sisted 60,000 pounds for 10 minutes. Saccharomyces albicans, Reess, 

 in one instance, resisted 60,000 pounds pressure for 10 minutes. Chop- 

 lin and Tammann, 4 as quoted by Hite and his colleagues, have stated 

 that yeasts could resist a pressure of 3000 kilograms per square centi- 

 meter (43.000 pounds per square inch). 



Antiseptics 



Nowak 5 found that ozonization had a detrimental effect on the 

 multiplication of yeast. It was brought out that this method may 

 be used to remove undesirable bacteria from yeast cultures. Lind- 

 ner and Grouven 6 employed four disinfectants towards yeast. These 

 were corrosive sublimate (ammonium), fluoride, formalin, and anti- 

 formin. Will and Wieninger 7 experimented with ozone on yeast. 



1 Regnard, P. Influence de la pression sur la levure. C. R. Ac. des Sciences, 

 98, 1884. 



2 Melsens. Comp. Rend. Ac. des Sci. 1870. 



3 Hite, B. H., Giddings, N. J., and Weakley, C. E. The effect of pressure 

 on certain microorganisms encountered in the preservation of fruits and vege- 

 tables. Bulletin 146, West Virginia University Agricultural Experiment Station, 

 1914. 



4 Choplin, G. W. and Tammann, G. Ueber den Einfluss hoher Eindruck an 

 Mikroorganismen. Zeit. Hygiene, 45 (1903), 171. 



5 Nowak, C. A. Influence of ozone on yeast and bacteria. Jour. Ind. Eng. 

 Chem. 5, 668, 1913. 



6 Lindner, P. and Grouven, O. What influence has an increase in the quantity 

 of yeast on the disinfecting power of various antiseptics. Wochschr. Brau. 30, 

 133-135. 



7 Will, H. and Wieninger. Zeit. f. d. ges. Brau. 1910. 



