=555. Methods of Examination.=—In general the methods of examination
are the same as those applied in the study of fresh meats. The contents
of water, salt and other preservatives, fat and nitrogenous matters are
of most importance. When not already in a fine state, the preserved
meats are run through meat cutters until reduced to a fine pulp. Most
potted meats are already in a state of subdivision well suited to
analytical work. The composition of preserved meats has been thoroughly
studied in this laboratory by Davis.[572]
=556. Estimation Of Fat.=—Attention has already been called to
the difficulty of extracting the fat from meats by ether or other
solvents.[573] In preserved meats, as well as in fresh, it is preferable
to adopt some method which will permit of the decomposition of the
other organic matters and the separation of the fat in a free state.
The most promising methods are those employed in milk analyses for
the solution of nitrogenous matters. Sulfuric or hydrochloric acid
may be used for this purpose, preference being given to sulfuric. The
separated fats may be taken up with ether or separated by centrifugal
action. A method of this kind for preserved meats, suggested by
Hefelmann, is described below.
About six grams of the moist preserved meat are placed in a calibrated
test tube and dissolved in twenty-five cubic centimeters of fuming
hydrochloric acid. The tube is placed in a water bath, quickly heated
to boiling and kept at that temperature for half an hour. About twenty
cubic centimeters of cold water are added and the temperature lowered
to 30°, then twenty cubic centimeters of ether and the tube gently
shaken to promote the solution of the fat. When the ether layer has
separated, its volume is read and an aliquot part removed by means of a
pipette, dried and weighed. The separation of the ethereal solution is
greatly promoted by whirling.
The mean proportions of the ingredients of preserved meats are about as
follows:
Per cent.
Water 67.0
Dry matter 33.0