Anthony Boucherie

"Fermentation is a spontaneous and intestine motion, which takes place amongst the principles of organic substance deprived of life, the maximum of which always tends to change the nature of bodies, and gives rise to the formation of new productions."

Bouillon la Grange.—Manual of a Course of Chymistry.

Fermentation has long since been divided into spirituous, acid, and putrid.

It is only since the revival or new epoch of chymistry, that the learned have been occupied in researches on fermentation. I was the first who gave a new hint on this important part of natural philosophy, in 1785. It was then held as certain, that the saccharine substance was the principle of spirituous fermentation. A series of experiments enabled me to demonstrate the contrary, for I obtained a well crystallized sugar by the fermentation of a substance which produces none by any other means.

In September, 1785, I read a memoir to the Academy of Sciences, at Paris. In that memoir I developed my theory. That learned body nominated four commissioners, for the purpose of examining my operations, and sanctioned my discovery by a report, in which it was acknowledged that I had discovered a new truth, and ordered the insertion of my memoir in the collection of those of the Foreign Associates. I attributed the principle of the spirituous fermentation to the mucilaginous substance. This has been since demonstrated, by attentively observing that it always begins with a motion of acid fermentation, which is produced by the mucilaginous substance. The European chymists have since reasoned upon fermentation; each of them has produced a new system; none have been able to bring it to a regular demonstration; and the learned Gay Lussac has said, that fermentation is one of the most mysterious operations of chymistry. Be that as it may, there are facts that are ascertained: let us endeavor to investigate them, that we may derive from them all the information which is necessary to us.

It is incontestable that spirits are produced by the saccharine substance. Grains, however, supply it, although they are not sensibly sweet. This has made me suspect that the fermentation is at first saccharine, which produces the sweet substance that is necessary for the formation of spirit. It is thus that, by a series of internal motions, the fermentation causes the formation of the spirit to be preceded by a slight production of acid; that it transforms the vinous liquor into vinegar, which the same fermentation changes in time into an animal substance, destroyed in its turn by the putrid fermentation. Such are the progressive changes operated by this all-disorganizing phenomenon, and the unerring march of nature to bring back all substances to their respective elements.

The necessary conditions for the formation of vinous fermentation, are—

• 1st. The presence of the saccharine substance.
• 2dly. That of a vegeto-animal substance, commonly called ferment, and soluble in water.
• 3dly. A certain quantity of water.
• 4thly. A temperature of 70° to 75°.
• 5thly. A sufficient mass.

When these are obtained, in a short time the liquor becomes turbid; it bubbles, from the disengaging of the carbonic acid gaz, and the heat increases considerably. After some days, these impetuous motions subside; the fermentation ceases by degrees; the liquor clears up; then it emits a vinous smell and taste. As soon as it ferments no more, it must be distilled. However, some distillers have asserted that a greater quantity of spirit is obtained when the liquor has acquired a certain degree of acidity. Others are of opinion that it must be distilled as soon as it is calm. I am of this opinion, because the acid can only be formed at the expense of a little of the spirit, which is one of the principles of the acetous acid. Besides, the longer the liquor remains in a mass, the more spirit is wasted by evaporation.