Fermentation

“ Fermentation now includes all changes in organic compounds brought about by ferments elaborated in the living animal or vegetable cell. There are two distinct types of fermentation: (1) those brought about by living organisms (organized ferments) , and (2) those brought about by non-living or unorganized ferments (enzymes) . The first class include such changes as the alcoholic fermentation of sugar solutions, the acetic acid fermentation of alcohol, the lactic acid fermentation of milk sugar, and the putrefaction of animal and vegetable nitrogenous matter. ”

“ As a specimen of the writer's humor, his account of what happens when fermentation comes to an end may suffice: "When the animals find no longer any sugar, they devour one another; and this they do in a peculiar manner. They digest the entire animal, excepting only the eggs, which pass through the intestinal canal unchanged, and so the residuum is still a fermentable substance, viz., the sperm of the animals, which remains over." ”

“ Fermentation is the process by which, under influence of air, warmth, moisture, and some ferment, sugar (or dextrose, starch converted into sugar) is changed into alcohol (C2H5HO) and carbon dioxide (CO2) . The product of all fermentation is the same. Three kinds are considered,—alcoholic, acetic, and lactic. Where bread dough is allowed to ferment by addition of yeast, the fermentation is alcoholic; where alcoholic fermentation continues too long, acetic fermentation sets in, which is a continuation of alcoholic. Lactic fermentation is fermentation which takes place when milk sours. ”

“ But in following the process of destructive fermentation as it takes place in large masses of tissue, animal or vegetable, but far preferably the former, as they lie in water at a constant temperature of from 60° to 65° F., it will be seen that the fermentative process is the work, not of one organism, nor, judging by the standard of our present knowledge, of one specified class of vegetative forms, but by organisms which, though related to each other, are in many respects greatly dissimilar, not only morphologically, but also embryologically, and even physiologically. ”

“ We have admitted, in our time, that alcoholic fermentation, instead of being an exception, is on the contrary the very type of the phenomena we are treating of; that the yeast-cells, far from being unimportant, take an essential part in it, and that in all fermentations whatever there occur low organizations, microscopic corpuscles, more or less analogous to those of yeast. ”

“ As regards fermentation producing alcohol, which may be effected by several different ferments, there will be as in the case of a given sugar, as many general equations as there are ferments, whether they be ferment-cells properly so called, or cells of the organs of living beings functioning as ferments. In the same way the equation of nutrition varies in the case of different animals nourished on the same food. ”

“ When we endeavour to apply the results of the investigations of the fermentation of sugar by yeast-juice, zymin, etc., to the process which goes on in the living cell, considerable difficulties present themselves. A scheme of fermentation in the living cell can, however, easily be imagined, which is in harmony with these results. ”

“ Fermentative Agents.—Fermentation in vegetable matter is always accompanied by the growth of living organisms. The development of these minute organisms is the exciting cause of fermentation and putrefaction. The germs or spores of some of these fermenting agents are always present in the air. It is well known to housekeepers that if a batter of flour and water and a little salt be kept in a jar of water at a temperature of from 100° to 110°, it will ferment in the course of five or six hours. ”

“ To conclude, fermentations occasioned in certain media, by the act of development and nutrition of ascertained microscopic animal or vegetable existences, present a group of well-defined characteristics. They follow obediently all the variations that may occur in the physiological activity of the microscopic beings contained in the liquid. This does not go into fermentation all at once; it delays more or less, and molecular movement makes itself perceptible in it by degrees. The phenomenon is one of evolvement. ”

“ The mass becomes heated and swells; carbonic acid gas is disengaged, and the sugar disappears and is replaced by alcohol. Now, as to the question of the origin of these spontaneous phenomena, so remarkable in character as well as usefulness for man's service, modern knowledge has taught us that fermentation is the consequence of a development of vegetable cells the germs of which do not exist in the saccharine juices within fruits; that many varieties of these cellular plants exist, each giving rise to its own particular fermentation. ”

“ Pasteur had at this time firmly established his thesis, no fermentation without life, both for alcoholic fermentation and for those other fermentations which are produced by bacteria, and had put upon a sound and permanent basis the conclusions drawn by Schulze, Cagniard-Latour, Schwann, and Kützing from their early experiments. It became generally recognised that putrefaction and other fermentative changes were due to specific organisms, which produced them in the exercise of their vital functions. ”

“ Those who have contradicted us have fallen into the error of supposing that the fermentation of fruits is an ordinary alcoholic fermentation, identical with that produced by beer yeast, and that, consequently, the cells of that yeast must, according to own theory, be always present. ”

“ The yeast produces fermentation, a process which may be thus described:— The dough re-acting upon the leavening matter introduced, the starch of the flour is transformed into saccharine matter, the saccharine matter being afterwards changed into alcohol, water, and carbonic acid gas. The dough must be well "bound," and yet allow the escape of the little bubbles of carbonic acid which result from fermentation, which in their passage cause the numerous little holes which are seen in light bread. ”

“ In that work we established for the first time that the lactic ferment is a living, organized being, that albuminous substances have no share in the production of fermentation, and that they only serve as the food of the ferment. M. Bechamp's note was even subsequent to our first work on alcoholic fermentation, which appeared on December 21st, 1857. It is since the appearance of these two works of ours that the preponderating influence of the life of microscopic organism in the phenomena of fermentation has been better understood. ”

“ Let us compare the action of ferment or yeast in a dried state to the action of albumen, which Liebig says is sufficient when decomposing to set up fermentation. "The white of eggs when added to saccharine liquors requires a period of three weeks, with a temperature of 96° F. before it will excite fermentation." [42] But any saccharine liquor on exposure to the air, though entirely destitute of albumen or gluten, will ferment, and the Torula may be found in it. I have found the Torula in a great variety of syrups which have spontaneously undergone fermentation. ”

“ One yeast-cell does not make a fermentation, and as no yeast is added a day is wasted whilst any yeasts which happen to be present are multiplying to an army large enough to produce a visible effect on the pulp. Any organism which happens to be on the pod, in the air, or on the inside of the fermentary will multiply in the pulp, if the pulp contains suitable nourishment. Each kind of organism produces its own characteristic changes. ”

“ The alcoholic ferments, therefore, present themselves to us as plants which possess at least two singular properties: they can live without air, that is without oxygen, and they can cause decomposition to an amount which, though variable, yet, as estimated by weight of product formed, is out of all proportion to the weight of their own substance. These are facts of so great importance, and so intimately connected with the theory of fermentation, that it is indispensable to endeavour to establish them experimentally, with all the exactness of which they will admit. ”

“ The presence of these germs determines the property of air of bringing about the processes of putrefaction and fermentation—that is the fundamental alteration of organic substances, which is accompanied by an entire change in their properties. The appearance of lower organisms, both vegetable and animal, is always to be remarked in these processes. Thus, for instance, in the process of fermentation, when, for example, wine is procured from the sweet juice of grapes, a sediment separates out which is known under the name of lees, and contains peculiar yeast organisms. ”

“ In both spontaneous and excited fermentation, there is a similar escape of a large quantity of elastic fluid, or carbonic acid gas, with a considerable proportion of spirit, and some of the water of the fermented fluid. This gas is known to form a considerable part of mucilaginous substances, as sugar, molasses, honey, malt, and other saccharine and fermentable matter.
Although the doctrine of fermentation, as a science, does not enable us to alter the spontaneous course of nature ”

“ When flour made into dough is kept for some time moderately warm, it undergoes spontaneous fermentation, formerly described as ‘panary fermentation,’ and supposed to be of a different nature from the fermentation which produces yeast. ”

“ Spirituous fermentation is that process of fermentation by which forms of yeast cells, by their growth and reproduction in such complex substances as grapes, fruit, apple juice, grains, etc., extract alcohol from these substances and by this process produce wine, cider, spirits, etc. ”

“ In the cases hitherto considered, the fermentation is proved to be the invariable correlative of life, being produced by organisms foreign to the fermentable substance. But the substance itself may also have within it, to some extent, the motive power of fermentation. The yeast-plant, as we have learned, is an assemblage of living cells; but so at bottom, as shown by Schleiden and Schwann, are all living organisms. Cherries, apples, peaches, pears, plums, and grapes, for example, are composed of cells, each of which is a living unit. ”

“ Of artificial ferments the variety is great, for besides all putrefying animal matters which contain nitrogen—such as blood, white of egg, glue, and flesh—certain mineral substances which act by souring the milk are also capable of exciting fermentation. ”

“ It was in vain urged by the housewife that God made yeast as well as dough, and loves fermentation just as dearly as he does vegetation; that fermentation develops the saccharine element in the grain, and makes it more palatable and more digestible. No, they wish the pure wheat, and will die but it shall not ferment. ”

“ Bacteriologists have been able to explain with a considerable degree of accuracy the object of this ripening. The process is really a fermentation comparable to the fermentation that takes place in a brewer's malt. The growth of bacteria during the ripening produces chemical changes of a somewhat complicated character, and concerns each of the ingredients of the milk. The lactic-acid organisms affect the milk sugar and produce lactic acid; others act upon the fat, producing slight changes therein; while others act upon the casein and the albumens of the milk. ”

“ A ferment is a substance containing nitrogen in a state of decomposition, which is able to excite fermentation in solutions of sugar; old cheese, putrefying flesh, blood, etc., all of them are ferments.
What is yeast?
We apply the term yeast to a particular species of ferment; the foam of beer (or of some similar liquor) , produced by fermentation.
Can you explain why it is that a body in a state of fermentation or putrefaction should cause unlimited quantities of similar matter to pass into the same state?
We only know the fact: the reason we are ignorant of. ”

“ This is accomplished by means of a little yeast from beer; and, when the fermentation is once excited, it continues of itself until completed. I shall, in another place, give an account of the effects of yeast, and other ferments, upon fermentable substances. I have usually employed 10 libs. of yeast, in the state of paste, for each 100 libs. of sugar, with as much water as is four times the weight of the sugar. I shall give the results of my experiments exactly as they were obtained, preserving even the fractions produced by calculation. [Pg 133]
Table I. Materials of Fermentation. ”

“ Any agent which destroys the life of the bacteria, or prevents their multiplication, breaks this circle and renders a cure possible.
The influence of bacteria in fermentation is still undecided, but, for the sake of completeness, the different opinions should be mentioned. It is admitted by all chemists that these or similar organisms are invariably present in some fermentations—Bacterium termo, or rod bacterium, in putrefaction, and the yeast-plant in alcoholic fermentation, for example ”

“ There are indeed the fruits of some trees that have a sweet and full juice, as grapes, cherries, apples, pears, figs, &c. which need not the addition of any ferment, having a natural ferment of their own, but other vegetables not so, being lean, as hearbs, flowers and roots. It is necessary there to promote the fermentation of them by the addition of a sutable ferment, lest in length of time these hearbs and seeds lose their spirit exhaling in maceration. ”