538. Sampling.—When possible the whole animal should constitute the sample. The relative weights of blood, intestinal organs, hide, hoofs, horns, bones and edible flesh are determined as accurately as possible. The general method of preparing samples of animal products is given in paragraph [5].
Fig. 114.
Fig. 115.
Fig. 116.
Names of Cuts of Meat.
The method of sampling employed by Atwater and Woods is essentially that just noted.[543] The sample, as received at the laboratory, is weighed, the flesh (edible portion) is then separated from the refuse (skin, bones etc.) and both portions weighed. There is always a slight loss in the separation, evidently due to evaporation and to small fragments of the tissues that adhere to the hands and to the implements used in preparing the sample. The perfect separation of the flesh from the other tissues is difficult, but the loss resulting from this is small. In sampling the material for analysis, it is finely chopped, either in a tray or in a sausage cutter, and in each case is well mixed.
539. Methods of Analysis.—The general methods for the analyses of food products are applicable to meats and animal products in general. In the separation of the nitrogenous constituents the methods described in paragraphs [411-414] are followed. It is not safe to estimate as proteids the total nitrogen multiplied by 6.25, since the flesh bases have much higher percentages of nitrogen than are found in proteid matters. As indicated in paragraph [280] the complete extraction of dried meats by ether is difficult of accomplishment. After a few hours it may be assumed that the total extract will represent the fat, although additional soluble matters are obtained by continuing the process. The heat producing power may be calculated from the analytical data secured. The methods which have been described in the preceding pages will be found sufficient for guidance in the examination of animal products, and the analyst will find them, when modified to suit particular cases, adapted to the isolation and estimation of proximate food principles.