boiling water there is less loss of protein matter than when the meat is placed in cold water and heated gradually. The substances removed in parboiling are water, fat, soluble mineral matter, and the meat bases. The fat is removed by becoming rendered, and rises to the surface where it can be skimmed off. A little over one percent of the protein content of meat is lost by parboiling while the total meat bases lost amount to almost one-third of the total quantity contained in the meat. Of mineral matter in the meat as high as 50 percent is lost in parboiling.
By shrinking, parboiling tends to make a more concentrated article and thus favors transportation. Practically the nutritive value of a pound of properly canned beef is about one-third greater than that of one pound of the fresh beef of the same kind. Hence parboiling may be regarded as a perfectly legitimate and desirable process without which the beef could not be properly prepared for canning.
Tinning.—After the meat is properly parboiled it is placed in the tins either by machinery or by hand. To each tin is added a small quantity of a liquid preparation made by the canners and known as soup liquor. This liquor generally contains salt, and sometimes a little sugar or molasses. The composition of soup liquor is as follows:
Solids, .92 percent
Protein, .09 "
Meat bases, .23 "
Ash, .28 "
Salt, .11 "
Water, 98.37 "
This soup liquor may be regarded as a thin soup. The origin of the liquid analyzed above was not disclosed, and, therefore, no expression can be made of the way in which it was formed. It was probably made from soup stock, namely, the waste meat and bones of the factory. There is no objection to a soup liquor of this kind provided it is made from sound, clean, and wholesome material. There are two reasons for adding this liquid, namely, to fill up the space which would otherwise exist between the pieces of meat and thus aid in the preservation of the material, and, second, to add a condimental substance which makes the contents of the tin more palatable.
Sterilization.—After the cans are filled in this way and closed by soldering or otherwise they are placed in retorts which are composed of strong iron or steel boilers, properly covered and secured, and when these boilers are full they are subjected to the action of steam heat under pressure. Usually a small hole is left in the can through which any gas, air or other kind, is expelled from the can. As soon as everything is complete the retorts are opened and the cans are sealed.
In all cases, however, after sealing the cans they are subjected to a second heating at a temperature of from 225 to 250 degrees F. The time of heating varies from one to two hours. After removal from the retorts the cans are washed
