462

FERMENTATION.

enjoy the property of causing a solution of sugar to ferment; with this difference, thatwhilst yeast can establish a complete fermentation in less than an hour, at a temperatureof about 68°, the above substances require several days, with a heat of from 77° to 87®!■■., for becoming ferments, and for occasioning fermentation. Substances devoid of nitro-gen do not produce a ferment.

FERMENTATION. (Eng. and Fr.; Gahrung, Germ.) When organic substances,under the influence of water, air, and warmth, are abandoned to the reciprocal operationof their proximate principles (sugar, starch, gluten, &c.), they are entirely changed anddecomposed, so that their ultimate principles (oxygen, hydrogen, carbon, and in some casesazote) combine in new proportions, and thus give birth to various new compounds. Tothis process, the general name of fermentation has been given. These operations andtheir products differ according to the differences of the substances, and of the circumstan-ces in which they are placed. The following may be enumerated as sufficiently distinctspecies of fermentation. 1. The saccharine fermentation, in which starch and gum arechanged into sugar. 2. The vinous fermentation, in which sugar is converted into alco-hol. 3. The mucilaginous fermentation, in which sugar is converted into slime, insteadof alcohol. 4. The acetous fermentation, in which alcohol and other substances are con-verted into vinegar. 5. The putrid fermentation or putrefaction, which characterizesparticularly the decomposition of azotized organic substances.

1. The saccharine fermentation. When a paste made by boiling one part of starchwith twelve parts of water is left entirely to itself, water merely being stirred in as itevaporates, at the end of a month or two in summer weather it is changed into sugar,equal in weight to from one third to one half of the starch, and into gum, equal to fromone fifth to one tenth, with a residuum of starch paste somewhat altered. This sac-charifying process advances much quicker through the co-operation of vegetable albu-mine or gluten, acting as a ferment. If we boil two parts of potato starch into apaste with twenty parts of water, mix this paste with one part of the gluten of wheatflour, and set the mixture for 8 hours in a temperature of from 122° to 167° F., themixture soon loses its pasty character, and becomes by degrees limpid, transparent, andsweet, passing at the same time first into gum, and then into sugar. The remainderconsists of the unchanged starch with the altered gluten, which has become sour, andhas lost the faculty of acting upon fresh portions of starch. It is probable, however,that the sugar formation in the first case, when the starch undergoes a spontaneouschange, may be due to the action of a small portion of gluten and albumine left "Jthe starch, since a putrefactive smell is eventually evolved indicative of that azotizeumatter. The gum into which during this process the starch is first converted, and whichbecomes afterwards sugar, is of the same nature as British gum, formed by the roastingof starch. .

This production of sugar takes place in the germination and kiln-drying of malt; on<the mashing of the brewer as well as the sweetening of bread in baking, rests upon thesame principles. In many cases the vinous fermentation precedes the saccharification;or accompanies it; the starchy parts of the fermenting mass changing into sng ar >while the previously formed sugar becomes wine or beer. In the sweetening of ’J. 111by keeping, a similar process occurs; the gummy and starchy fibres become sugarthe action of the glutinous ferment which they contain; as happens also to the juicesmany fruits which sweeten for a little while after they have been expressed. . _

The nature of this sugar formation through the influence of gluten upon starch, isdoubtedly the same as the conversion of starch into sugar, by boiling it with sulphacid; though the whole theory of this change is not entirely developed. ,, 0 f

The most energetic substance for the conversion of starch into sugar, is the m a . gbarley. According to the researches of Payen and Persoz, the gum which by ^process is first formed, may be prevented from going into sugar, by merely exposing ^to a boiling heat, and hence we have it in our power either to make sugar or^g ..pleasure. Of finely ground malt from 10 to 25 partsmust be taken for 100 parts ol s^ ^ ,Into a pan placed in a water bath, 400 parts of water being warmed to from 77° W j qqthe ground malt mhst be stirred in, and the temperature must be raised to 140°. s£ dparts of starch must now be added, and well mixed. The heat -is then to be me ^to 158° F.; and be so regulated that it shall not fall below 149°, nor rise c0I ne

In the course of 20 or 30 minutes the originally milky and pasty liquid wil -j'liisgradually more attenuated, and eventually it will turn as fluid nearly as wa,er ’ hs t a nceis the point of time in which the starch has passed into gum, or into the sulately denominated dextrine by the chemists. Should this mucilaginous matte , te>

appears to be a mixture of gum and a little starchy sugar, be wished for m a ,the temperature of the liquid must be suddenly raised to the boiling point, wa er ; ^further action of the malt upon it is stopped. But on the other hand it s “-o fardesired, then the temperature must be steadily maintained at from 158 to becomethree quarters of an hour, in which time the greater part of the starch will a