Rapidity of Operation.—Five men—one to handle the boxes of grapes, two to stem, standing on opposite sides of the stemmer, one to operate the crusher, and one to take the stems and remove the remaining grapes and to make himself generally useful—can stem and crush with these hand machines twenty tons of grapes per day, enough to make three thousand gallons of wine. And the work can be done much more rapidly by the use of the stemmer and crusher combined, which is to some extent used in the largest establishments.
Special Practice.—Boireau says that it has been observed that of the Médoc wines, those made without crushing the grapes have less color than those made from grapes of the same crop which have been crushed, but that they have a more refined and delicate taste (plus fins de goût), and that consequently many of the proprietors of the grands crûs of the Médoc in those years which are favorable to the maturity of the grape do not crush; they only do it in inferior years, when the grapes have not become sufficiently ripe, and when they fear that the wine may not have a suitable color. And in another place he tells us that in those grand wines which are intended to be bottled, a superabundance of tannin and its consequent roughness may be avoided by complete stemming, fermenting the whole berries, and by drawing from the fermenting vat at just the right time.
CHAPTER V.
FERMENTATION—ITS CAUSES.
It is with some hesitancy that I attempt to give a brief summary of the results of scientific investigation into this subject, for fear of going beyond the legitimate limits of a practical work, as this book is intended preëminently for practical men. But as the work would be incomplete without it, and as a knowledge of the general phenomena of fermentation, and of the different influences to which it is subject, are of vast importance to those who will intelligently apply their principles, I give the following as but a brief resumé, and will put it as plainly as the subject will permit. Most of the ideas given below are extracted from Schutzenberger’s work on fermentation.
There are several different kinds of Fermentation, as (1) vinous, alcoholic or spirituous fermentation; (2) mucous or viscous fermentation; (3) lactic fermentation; (4) ammoniacal fermentation; (5) butyric fermentation; (6) putrifaction; and (7) acetic fermentation, or fermentation by oxidation, and others.
Alcoholic Fermentation is that which sugar undergoes under the influence of the ferment or yeast; and it is now agreed that this ferment consists principally of an aggregation of living organisms, or an assemblage of microscopic cells.
The Yeast Plant.—Our author gives them the name of saccharomyces cerevisiæ, following those who consider it to be a species of fungus, and states that it is now very generally admitted that ferments are fungi, although by some they have been considered animal in their nature. These cells are round or oval, and are from .00031 to .00035 of an inch in their greatest diameter. “They are formed of a thin and elastic membrane of colorless cellulose, and of a protoplasm, also colorless, sometimes homogeneous, sometimes composed of small granulations.” The cells are separate or united two by two. When they are deposited in a fermentable liquid, as a sugar solution or a must, small prominences are seen to arise at one or rarely two points, the interior of which is filled with protoplasm from the mother cell; these prominences grow until they have attained the size of the original cell, when the base contracts, forming a kind of neck, and immediately they separate from the mother cell, and under favorable conditions one cell produces several generations, but by degrees it loses all its protoplasm, which at last unites in granules swimming in super-abundant cellular juice. The cell ceases to produce, and dies; the membrane is ruptured, and the granular contents are diffused in the liquid. In the manufacture of beer the fermentation is of two kinds: surface fermentation and sedimentary fermentation, depending upon a high or a low degree of heat. The surface saccharomyces develop more rapidly than the others, are larger, and they bud so rapidly that the cells which issue from each other do not separate, but remain attached, forming ramified chains of from six to twelve or more buds. The bubbles of rising gas have a greater hold on these chaplets than on single cells, which causes the newly formed yeast to rise to the surface during active fermentation. These organisms or fungi produce spores which are sown on the surface of fruits, and get into the juice by crushing, when they commence their reproduction by budding. So that the basis or cause of the phenomena which we call fermentation is the growth and reproduction of yeast or ferment, which is made up principally of the minute organisms just described.
Functions of Yeast.—Yeast is a living organism, belonging to the family of fungi, genus Saccharomyces, destitute of mycelium, capable of reproduction, like all the elementary fungi, by buds and spores. Its composition singularly resembles that of other vegetable tissues, and especially the plants of the same family. It does not differ essentially from other elementary cells, unprovided with chlorophyll.
Normal Conditions of the Life of Yeast.—The conditions which our author calls normal in the life-history of yeast, are those in which it develops itself and increases with the greatest activity and energy. They are of two orders, physical and chemical.
With respect to physical conditions, it is only necessary to notice the temperature. That most favorable to the nutrition of yeast, and that which is found advantageous to other cellular vegetable organisms, is between 25° C. and 35° C. (77° and 95° F.) Above and below these limits, the vital manifestations do not cease until we descend below 9° C. (48.2° F.), or rise above 60° C. (140° F.), the temperature at which albuminoid principles begin to coagulate.