On expressed yeast-cell plasma (Buchner's "Zymase") / by by Allan Macfadyen, M.D., G. Harris Morris, and Sydney Rowland, M.A. ; communicated by Sir Henry E. Roscoe, F.R.S.

  • Macfayden, Allan, 1860-1907
Date:
[1900?]
Catalogue details

Licence: In copyright

Credit: On expressed yeast-cell plasma (Buchner's "Zymase") / by by Allan Macfadyen, M.D., G. Harris Morris, and Sydney Rowland, M.A. ; communicated by Sir Henry E. Roscoe, F.R.S. Source: Wellcome Collection.

    10/22 (page 257)
    Influence of Age of Yeast on Activity of Juice.—In Table I] we give some of our results on the influence of the age of the yeast, i.e., the time which elapsed between the time of collection of the yeast in the brewery, and that of pressing and grinding, on the activity of the cell plasma obtained. The same table shows to some extent the influence of sugar concentration on the amount of gas evolved. It will be seen that the results are very variable, but that the general tendency is for the activity of the juice to increase to a certain point with the age of the yeast, the maximum being reached about the 3rd or 4th day from collection. After the maximum is reached there is a very rapid decline in the activity of the juice. The variation in the amount of auto-fermentation is not so great, but the! tendency of this is to follow the same direction. The results arej shown diagrammatically in figs. 1 and 2, the former showing the auto- fermentation and the latter the fermentation in presence of sugar, both when the gas evolved from the auto-fermentation is included and when it is deducted from the total amount. Fig. 1.—Showing the influence of age of yeast on auto-fermentation after 48 hours. ASe of yeast in days. This increase up to a certain point of the activity of the juice with the age of the yeast is the reverse of that which takes place with bottom- fermentation yeasts, as described by Buchner and other Continental observers. Influence of Storage on Activity of Juice.—When the expressed juice is kept even at or below freezing point, its power both | of auto-fermenta¬ tion and of decomposing sugar rapidly diminishes. Influence of Amount of Sugar 'present.—We carried out a series of