FIG. 153.—FILTER PRESS.
When it is compounded with the lard, the desired amount should be put into the kettle with the lard after it is treated. The same is true of oleo-stearine, except that in the bleaching of this article from one-half to one and one-half per cent of fuller earth is sufficient. Measures must be taken to see that ingredients are intimately mixed before passing the product to the rolls.
The use of tallow or stearine is for the purpose of cheapening the product, as well as hardening it, the formula for same being made according to the values and conditions under which the lard is to be sold. For instance lard going south, or into a warm climate, is made much harder than lard for a temperate climate; hence lard formulas, generally speaking, are worthless for general use, the different formulas being made to suit widely different conditions, and their availability also depends to a considerable extent upon the fluctuation of values.
Filter Press.
—After the contents of the kettle have been pumped through the filter air pressure should be turned into the filter press in order to blow out all the lard possible. After this live steam should be turned on, expelling the balance of the lard from the pipe. A large portion of this latter lard, however, is unfit to be used again, as it contains sediment and fullers earth combined, having a rank, strong odor, and can be used only for grease.
FIG. 154.—LARD COOLING CYLINDER.
Lard Roll.
—This is a device provided for cooling lard in a film so as to bring plenty of air in contact with the surface during the congealing. After the lard has been put through the filtering press it goes to a receiving tank and is next passed over rollers for chilling. ([Fig. 154].) These are cast iron cylinders containing refrigerated brine. The cylinders revolve at from ten to fourteen revolutions per minute, the lard being congealed on the outer surface. Fixed against the side of the cylinder is the edge of a steel knife which scrapes close to its surface. The lard, in contact with the cool surface of the cylinders, congeals and as it passes to the knife it is removed and drops into the trough. Here it is thoroughly beaten by a revolving shaft with pickers on it, so that all lumps are broken and the grain is of a smooth, even consistency. Pure lard passes to an agitator, which is a jacketed kettle, where it is given a thorough agitation and drawn off cool as possible, the object being to have the different ingredients thoroughly mixed at a low temperature.
At times rolls are used in tandem. When a bountiful supply of cold water, say at 60° F., is available, the saving in refrigeration justifies the use of tandem rolls. In this instance the first roll is elevated so as to gravitate the lard to the feed of the second.