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the centre and sometimes near the coating. These are shown on Plate LV., Fig. 1.
Gluten was next selected for experiment. A sample was carefully prepared from wheaten flour, and a portion was introduced into a cane sugar solution. The gluten at first floated on the surface of the liquid, but in a few days it became much disintegrated and subsided to the bottom of the flask, and afterwards became gradually diffused throughout the liquid.
On the second or third day an action was observed in the sample, and small transparent cells were seen to be tolerably abundant, but they did not appear to possess much action. The sample was frequently examined for alcohol, but very little was found to have been produced ; and at the end of thirty-four days it only contained 1.65 per cent. of alcohol and 24 per cent. of acid.
The spores or cells in this case had a bright nucleus similar to that which characterized the egg albumen cells. The gluten cells are represented on Plate LV., Fig. 2.
Wheaten flour albumen was next tried, and in the first instance a cold-water flour extract was prepared, the starch and other insoluble constituents being separated by filtration. The clear filtrate containing the albumen in solution was divided into two portions; to one 21:80 per cent. of glucose was added, and to the other about 15 per
cent. of cane sugar. In a day or two after the samples had been prepared they were both found to be full of microscopic animals, of which some were ovoid in form, and others consisted apparently of several minute joints. The portion to which the cane sugar had been added soon became thick and syrupy, and it was apparent that the sugar was being converted into mucilage.
The transformation of the cane sugar in a cold-water flour extract was a result which was entirely unexpected, and it is probable that the change in the sugar was induced through the operations of the little creatures present in the solution, for they all appeared to be extremely active, and apparently devouring some substance in solution.
At the expiration of twenty-four days the sample was examined for alcohol and acid, and it was found to contain six-tenths per cent. of acid, * but no alcohol.
The portion of the extract to which glucose had been added became turbid and slightly mucilaginous ; and at the expiration of twenty-four days the sample was examined for alcohol and acid, and it was found to contain · 72 per cent. of acid but only 0.17 per cent. of alcohol. There were present in the sample a few cells resembling those of yeast, but they appeared unhealthy and inactive.
* The acid is estimated as acetic.
From these results it was obvious that in order to study the ferment which wheaten flour albumen would give rise to, the albumen would have to be separated and introduced directly into the sugar solution.
A small quantity was therefore prepared by heating a coldwater flour extract, and separating the coagulated albumen by filtration. The albumen after having been well washed was introduced into a solution containing 15.62 per cent. of glucose. The sample was examined daily and was found to be free from microa scopic animals, and remained so for about a week although the air had access to the liquor through a glass tube.
At the end of fourteen days the sample was examined for alcohol and acid, and was found to contain neither. In the meantime mycelium was observed developing throughout the albumen, and giving rise to transparent spores or cells with a bright nucleus similar to those that occurred in the other albumen sugar solutions.
The sample was again examined for alcohol at the end of a month and was then found to contain one-tenth per cent.
Another small quantity of albumen from flour was prepared by precipitating the albumen from the cold-water extract by alcohol. The precipitated albumen was then diffused through water which was afterwards heated for some time to drive off the alcohol, and about 15 per cent. of glucose was added to the albuminous liquid. On the following day, however, the sample was found to contain a considerable number of the microscopic animals which it was intended to get rid of. In fact a large proportion of these creatures present in the flour extract was enclosed in and carried down with The precipitate.
At the end of fourteen days the sample was examined for alcohol and acid, and was found to contain: 12 per cent. of acid, but no alcohol. Now it will be observed that the result in this case is different from that obtained in the experiment with the albumen which had been prepared by coagulation, in the one case there were microscopic animals present, while in the other they were absent.
This sample was again examined for alcohol at the end of twenty-eight days, when it was found to contain •19 per cent. .
In this experiment, the mycelium developed in the albumen was similar to that formed in the albumen prepared by coagulation.
Albumen was prepared from ground malt in exactly the same manner as in the case of the flour, and the like experiments were performed with it in sugar solutions with almost identical results. The albumen prepared from the malt extract by heating was also found to be entirely free from microscopic animals, while that obtained by precipitation abounded with them. The mycelium and spores developed in the flour and malt albumen are represented on
Plate LV., Figs. 3 and 4. Some yeast cells, however, as might be expected, were found in the sample to which the malt albumen that had been precipitated by alcohol was added, and it was found to contain a larger percentage of alcohol than any other of the albuminous samples.
The experiments in the case of the malt were carried a little farther. Cane sugar was added to the malt extract from which the albumen had been separated by heating, and although the liquid in a short time afterwards was alive with minute creatures, the sugar was not converted into mucilage, and in the course of a few days natural fermentation set in.
The extract of malt from which the albumen had been precipitated by alcohol was also operated upon. When the precipitated albumen had been separated by filtration, the alcohol contained in the filtrate was removed by distillation, and to the residue about
per cent. of cane sugar was added. On the fourth day fermentation set in, and the ferment produced was the purest and finest specimen that I have seen, and the sample was entirely free from microscopic animals, &c.
In fact the animals and germs that escaped being carried down by the alcoholic precipitate appeared to have been subsequently destroyed by long boiling in distilling off the alcohol. At the end of ten days the sample contained 10.63 per cent. of alcohol, and only 18 per cent. of acid; so that, after all the manipulation through which the extract was put, the natural ferment produced possessed considerable powers, and which were still unexhausted.
The various germs and organisms infesting grain are the most formidable enemies with which we have to contend in the fermentation of grain extracts. If these once obtain possession of the field, and gain the ascendency, they materially interfere with the success of the fermentative process.
A temperature of about 175° Fahr., at which grain extracts are usually prepared, is not sufficient to destroy the animals and germs; their vitality may be suspended, but if the subsequent conditions are favourable to their growth, they become revivified.
To determine the effect which boiling has upon the fermentation of a malt extract, a comparative experiment was made. An infusion of malt was prepared and kept for two hours and a half at a temperature between 170° and 180° Fahr. The extract was then divided into two portions, one of which was boiled for some time, and afterwards about 15 per cent. of glucose was added to each portion. At the end of ten days the portion which had been boiled contained 10:38 per cent. of alcohol and 0.27 per cent. of acid, while the other contained 0.78 per cent. of acid and only 6.26 per cent. of alcohol.
In the one case the yeast cells had had possession of the field
first, whereas in the other it was simultaneously occupied by a variety of organisms.*
A cold-water extract of barley meal also possesses the property of converting cane sugar into mucilage, but the yeast cells soon develop, and resolve the greater portion of it into alcohol and carbonic acid gas. This is a most interesting phenomenon, and it serves to convey some idea of the wonderful power and singular properties of the yeast plant.
Under the microscope the yeast cells can be seen in the mucilaginous mass, sometimes in bundles resembling a bunch of grapes, and sometimes in a chain-like form, and also that the multiplication of the cells is carried on by a process of budding, Plate LV., Fig. 5.
This mucilaginous form of solution will afford an excellent opportunity of studying the development and growth of the yeast plant, and be the means of finally settling the question as to its true vegetable origin. Cane sugar is not converted into mucilage in all extracts prepared from barley meal. In a great many cases, especially at this season of the year, and under the influence of a high temperature, the yeast cells begin to act soon after the preparation of the extract and counteract the formation of mucilage.
The formation of mucilage is also prevented if, before the addition of the sugar, the extract is boiled for about half an hour in order to destroy the microscopic animals present.
In cold-water extracts of malt, to which cane sugar has been added, the cane sugar is not converted into mucilage, as in the case of barley meal and wheaten flour extracts. There is at first a slight tendency to thickening, but there appears to be an opposing action set up in the malt extract which prevents the formation of mucilage.
With malt extracts prepared in the cold very fair fermentations can be obtained; but as the samples are primarily occupied by a variety of organisms, a large percentage of acid is produced, and considerable loss of alcohol sustained.
The results hitherto obtained point to the microscopic animals as being the proximate cause of both the transformation of cane sugar into mucilage, and the production of acid; and the change effected in the sugar especially tends to the inference that the action is a catalytic one. It is hardly possible to believe that these
a creatures could have devoured so large a quantity of sugar in so short a time, or that having devoured it they would have reproduced it in a mucilaginous form.
Moulds and Pus.—A few experiments have been made with certain moulds, and one with pus, to determine their respective actions in sugar solutions.
The study of the development and properties of moulds, like , that of most matters connected with fungi, is undoubtedly a critical one, as is fully evidenced by the absence of an agreement of opinion on the subject.
* There has been a considerable difference observed in the number of animals and germs present in different samples of malt.
My inquiry has been directed to the action of moulds rather than to determine their origin and mode of development, but as it is alleged by some that the blue mould of malt is the ultimate development of the yeast plant, I cannot help stating that I have failed in my experiments to identify it as such ; on the contrary, the moulds appear to preserve their distinctive character, and to be identified with a more advanced stage of decomposition than the true yeast plant; and, as a rule, wherever they occur they leave unpleasant evidences, which is certainly not the case with the yeast plant.
It is not improbable that there is some relation subsisting between the yeast plant and certain of the moulds, but whatever the connection is, it is obviously not yet understood, and remains to be determined.
A quantity of blue mould with the pasty mass attached was collected from the surface of moistened ground malt, and introduced into a sugar solution containing 15 per cent. of glucose, and the sample was placed in a chamber maintained at a temperature of 70° Fahr.
On the third day the liquid was alive with microscopic animals, and carbonic acid gas was being eliminated. On the fourth day it contained 18 per cent., and on the sixth day .28 per cent. of acid, and · 17 per cent. of alcohol. On the ninth day it contained 1.34 per cent. of alcohol and ·42 per cent. of acid ; and at the end of twenty-eight days 7.48 per cent. of alcohol and 60 per cent. of acid.
On the seventh day the cells or spores were observed to be mixed in character, some elongated cells similar to those found in malt fermentations having sprung into existence; and it will be observed that it was subsequent to this that the alcohol began to be produced in an appreciable quantity, so that the probability is that some yeast cells were produced, for the addition of the mould crust was equivalent to adding a portion of malt extract.
At the end of twenty-eight days the liquid was drawn off, and the residue at the bottom was introduced into a fresh solution of sugar; and at the expiration of eighteen days the sample was examined, and found to contain about 2 per cent. of alcohol.
The mould up to this time not only maintained its identity, but it will be seen from the representation on Plate LV., Fig. 6, that it was propagating in the liquid in the brush or plume-like form, after the fashion of its aërial fruiting, and that the spores are distinguished from yeast cells by a central ring, instead of containing granular matter.