A Practical Treatise on Brewing/Appendix/Spontaneous Fermentation

2030368A Practical Treatise on Brewing — Appendix: Spontaneous FermentationWilliam Black

SPONTANEOUS FERMENTATION.

It being a disputed point whether the vinous fermentation would take place, in worts or wash, when the air is excluded, without any addition of yeast or other ferment, we shall here introduce minutes of an experiment, which was made under our notice, and which appears very conclusive. The quantities operated upon were but small, being only two pints of distiller’s wash. One pint at a gravity of 75.2 by Bates’ instrument, was put into a common wine bottle, which was well corked, and a piece of bladder tied tightly over the cork, so as to exclude all extraneous matter: the gravity of the other pint was 41.5 by the same instrument, and was put into another bottle, and treated precisely as above, no yeast was employed. The two bottles were then suspended in a distiller’s wash-back, which had just been pitched at a temperature of 66°, with the usual quantity of yeast.

Date of observation 1839 No. 1 Bottle No. 2 Bottle
Degrees of temperature. Gravity. Degrees of temperature. Gravity.
5, P. M.
Jan. 24
52 75.2 54 41.5 Bottles placed in square.
25 68 75.0 66 41.5 Wash-back 71°, no appearance of fermentation in either bottle.
26 70 73.2 70 41.1 Back in which bottles were placed 80°. No. 1 bottle a creamy head. No. 2 a frothy head, and on drawing the cork a hissing noise was heard, fermentation in both pretty strong.
28 66 49.6 68 17.8 No. 2 bottle, the gas, on cutting the string of the bladder over the cork, forced it out violently, and the contents commenced working over like brisk beer.
29 62 34.2 62 15.2 A frothy light yeasty head on both bottles, on No. 1 being uncorked, carbonic acid gas escaped, which blew out a candle. No. 2 also discharged gas with considerable force, and a portion of yeast adhered to the bottoms of the cork.
30 58 27.8 60 13.0 No. 1 bottle still a yeasty-like head. No. 2, head nearly disappeared; carbonic acid still apparent in each.
Feb. 1 25.4 11.4 Went to still.

The above samples were carefully distilled in a retort, and the relative products according to the attenuation were not far different from the washback in which they had been placed, and which had been fermented in the regular way, and was rather below 0. The bottle No. 1, produced at the rate of a gallon of spirits for every 5.4 attenuated; and No. 2 at the rate of a gallon for every 5 attenuated; while the back produced a gallon for every 4.5 attenuated.

The above experiment was made in the Government Experimental Distillery in the year 1840, by two experienced revenue officers, and under the author’s inspection, while employed by Dr. Birkbeck in conducting certain operations then under investigation.