The fact is that the constitution of average grape juice and the temperatures of fermentation which generally prevail are particularly well suited to the life action of wine yeast, and are inimical to the development of the other organisms. When these conditions fail, as is, for instance, the case when the must is lacking in acidity, or when the weather during the fermentation period is very hot and means are not at hand to cool the must, bacterial side fermentations may, and do, often take place.
According to Louis Pasteur, about oth of the sugar transformed under ordinary conditions in the fermentation of grape juice and similar saccharine liquids into alcohol and other products becomes converted into glycerin.
In view of the fact that fresh grape juice contains innumerable bacteria and moulds, in addition to the yeast cells which bring about the alcoholic fermentation, and that the means which are adopted by the brewer and the distiller for checking the action of these undesirable organisms cannot be employed by the wine-maker, it is no doubt remarkable that the natural wine yeast so seldom fails to assert a preponderating action, particularly as the number of yeast cells at the beginning of fermentation is relatively small.
But place the crushed fruit or the wounded animal under conditions which preclude the presence or destroy the life of the germ, and again no change takes place; the grape juice remains sweet and the wound clean.
During the alcoholic fermentation of grape juice it is deposited in the form of an impure acid potassium tartrate which is known as argol, and when purified as cream of tartar.
He poured carbonated red grape juice into a long-stemmed glass and set the bottle back in the refrigerator.
The sugar in ripe grape juice is practically invert sugar, i.e.
It is probable that the discovery that an intoxicating and pleasant beverage could be made from grape juice was purely accidental, and that it arose from observations made in connexion with crushed or bruised wild grapes, much as the manufacture of beer, or in its earliest form, mead, may be traced back to the accidental fermentation of wild honey.
Dextro-tartaric acid occurs in the free state or as the potassium or calcium salt in grape juice and in various unripe fruits.