The beet-root rasp of Moulfarine is represented in [figs. 1098], [1099.] a, a, is the frame-work of the machine; b, the feed-plate made of cast iron, divided by a ridge into two parts; c, the hollow drum; d, its shaft, upon either side of whose periphery nuts are screwed for securing the saw blades e, e, which are packed tight against each other by means of laths of wood; f, is a pinion upon the shaft of the drum, into which the wheel g works, and which is keyed upon the shaft h; i, is the driving rigger; k, pillar of support; l, blocks of wood, with which the workman pushes the beet-roots against the revolving-rasp; m, the chest for receiving the beet-pap; n, the wooden cover of the drum, lined with sheet iron. The drum should make 500 or 600 turns in the minute.
A few years ago, M. Dombasle introduced a process of extracting the juice from the beet without either rasping or hydraulic pressure. The beets were cut into thin slices, by a proper rotatory blade-machine; these slices were put into a macerating cistern, with about their own bulk of water, at a temperature of 212° F. After half an hour’s maceration, the liquor was said to have a density of 2° B., when it was run off into a second similar cistern, upon other beet-roots; from the second, it was let into a third, and so on to a fifth; by which time, its density having risen to 51⁄2°, it was ready for the process of defecation. Juice procured in this way is transparent, and requires little lime for its purification; but it is apt to ferment, or to have its granulating power impaired by the watery dilution. The process has been accordingly abandoned in most establishments.
I have seen the following operations successfully executed in a beet-root factory near Lille, and have since verified their propriety in my own laboratory upon white beets, grown near Mitcham in Surrey. My product was nearly 5 per cent.; it was very fair, and large grained, like the vacuum-pan sugar of Demerara, but without its clamminess.
The roots were washed by a rotatory movement upon a grating made like an Archimedes’ screw, formed round the axis of a squirrel-cage cylinder, which was laid horizontally beneath the surface of water in an oblong trough. It was turned by hand rapidly, with the intervention of a toothed wheel and pinion. The roots, after being sufficiently agitated in the water, were tossed out by the rotation at the end of the cylinder furthest from the winch. They were next hoisted in a basket up through a trap hole into the floor above, by means of a cord and pulley moved by mechanical power; a six-horse steam engine, upon Woolfe’s expansive principle, being employed to do all the heavy work. They were here subjected to the mechanical grater (rape mécanique), see [fig. 1098], [1099.], which had, upon its sloping feed-table, two square holes for receiving at least two beets at a time, which were pushed forwards by a square block of wood held in the workman’s hand by means of a strap. The rasp was a drum, having rows of straight saws placed half an inch apart round its periphery, parallel to the axis, with teeth projecting about 1⁄8 of an inch. The space between each pair of saws was filled with a wedge of wood. The steel slips, or saw plates, were half an inch broad, twelve inches long, and serrated on both their longitudinal edges, so that when the one line of teeth was blunted, the other could be turned out. The drum made 750 turns per minute.
The pulp from the rasp fell into a flat trough placed beneath, whence it was shovelled into small bags. Each bag had its mouth folded over, was laid upon a wicker plate, and spread flat with a rolling-pin. The bags and hurdles were then piled in the hydraulic press. There were three presses, of which the two allotted to the first pressure were charged alternately, and the third was reserved for a final and more durable pressure of the marc. See [Press, hydraulic], and [Stearine Press].
The juice flowed over the edges of the wicker plates, and fell into the sill-plate of the press, which was furnished with upright borders, like a tray, through whose front side a pipe issued, that terminated in a leathern hose, for conducting the juice into an elevated cistern in the boiling-house. Here one pound of slaked lime was mixed with every four hectolitres (about 88 gallons imp.) of juice. The mixture was made to boil for a little while in a round pan alongside, whence it was decanted into oblong flat filters, of blanket stuff. The filtered liquor, which had in general a spec. gravity of 15° Baumé, (about double that of the fresh juice), was now briskly concentrated by boiling, in an oblong pan, till it acquired the density of 28° B. The fire being damped with raw coal, the syrup was run off rapidly by a stopcock into a large basin with a swing handle, and immediately replaced by fresh defecated liquor. The basin was carried by two men to the opposite side of the boiling-house, and emptied into a cistern set on a high platform, whose horizontal discharge-pipe was provided with a series (five) of stopcocks, placed respectively over five copper chests (inverted truncated pyramids), containing a thick bed of granular bone black, covered with a perforated copper plate. The hot syrup thus filtered had a pale straw-colour, and was subsequently evaporated in swing pans, [figs. 1096], [1097.], over a brisk fire, in quantities equivalent to half a cwt. of sugar, or four hectolitres of average juice.
MAPLE SUGAR.
The manufacture of sugar from the juice of a species of maple tree, which grow spontaneously in many of the uncultivated parts of North America, appears to have been first attempted about 1752, by some of the farmers of New England, as a branch of rural economy.
The sugar maple, the Acer saccharinum of Linnæus, thrives especially in the states of New York and Pennsylvania, and yields a larger proportion of sugar than that which grows upon the Ohio. It is found sometimes in thickets which cover five or six acres of land; but it is more usually interspersed among other trees. They are supposed to arrive at perfection in forty years.