Even in meat that appears lean much fat is present lving between the muscle fibres. This may be seen upon heating the meat in water, when globules of fat appear from even the leanest meat. The solidity of the fat is due chiefly to the stearin that is present.
The amount of water in meat varies very much. A lean cut of beef may have as much as seventy-five per cent of water, while a fat piece might not contain more than fifty per cent. In general the more fat the less water there is present, so that in buying it is economy to select meat that is moderately fat.
From the standpoint of digestibility, meat is an excellent food. It is among the most easily digested of the proteid foods. As a rule raw meat is more digestible than cooked, and rarely cooked meat more digestible than that which is well done. The cooking of meat has its value not in adding to the digestibility but in developing flavor, so that the meat becomes more palatable; and in rendering it more safe, by destroying certain parasites that are sometimes present in raw meat, particularly in pork, and bacteria that under certain circumstances may cause dangerous decomposition.
There is much difference in the digestibility of dh-ferent meats. Pork is ranked among the less digestible meats, since it requires a longer time for complete digestion than do other varieties. This is probably due to the large amount of fat closely combined with the muscle fibres. Bacon fat, on the other hand, from its different form, is generally found to be easily digested.
Mutton and beef stand equally well in this respect. As has been suggested before, short fibred meats are in general more easily digested than long fibred ones, yet veal is an exception to this. Hutchison explains this by suggesting that the fibres of veal easily elude the teeth on mastication, and that the comparatively insipid character of the veal fails to excite a free flow of gastric juice. It would seem that this absence of extractives would be the more important factor.
How far the cooking of meat alters its chemical composition is not wholly determined. Some interesting experiments at the University of Illinois have taught us much about the losses that take place in the cooking. It is shown that in whatever way meat is cooked, there is much loss of weight, amounting either in boiling or in roasting to a fourth or even a third of the original weight. This loss is partially proteid and fat, but consists still more largely of water. The loss of water appears to be caused partly, at least, by the hardening and consequent contraction of the muscle fibre, the water being mechanically forced out.
An interesting experiment has been tried in regard to the effect of salt in preventing or accelerating the losses in meat. A salt solution was prepared, having the same density as that of the juices of the meat, and a piece of meat was boiled in this. It was found that a very small amount of the juices of the meat were lost in the water and practically none of the salt penetrated into the interior of the meat. The conclusion drawn was that very little interchange of the water and the meat juices could take place unless the medium in which the meat was cooked was either less or more dense than the meat juices themselves.