This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Meat soups are made by continued boiling, which converts the connective tissue of meat fibres into gelatin, which is gradually dissolved into the water. The soup thus becomes an aqueous solution of gelatin, with some of the extracts of the meat for flavouring. Whatever albumin is dissolved and what little fat may be melted forms a scum on the surface. The insoluble albumin becomes coagulated and floats about in small particles, which are strained away if the soup is to be clear, but this process makes it less nutritious for invalids. If a really rich soup or nutritious broth is to be made from any piece of meat, so much of the latter is dissolved into the water that the residue is tasteless, tough, and so indigestible that it is practically useless. On the other hand, there are many scraps of meat or parts which are unsightly or less useful for food from which very nutritious broth may be made, and the inedible bones are utilised in the same manner.
The extent to which soups and broths may be made nutritious depends largely upon the character of the meat used, and Parkes placed meats in the following order in regard to the nutritive value of their broths, commencing with the strongest: Chicken, mutton, and beef. He said that the best broth made from beef contains 150 grains of nitrogenous nutriment to the pint and 90 grains of salts, for nearly all of the salts of the beef, chiefly chlorides and phosphates, dissolve out into the surrounding water.
When a few drops of dilute hydrochloric acid are added to minced meat immersed in water, the acid converts the muscle albumin into syntonin, which is soluble in cold water, and after soaking in it for several hours a moderately nutritious broth can be obtained. Such broth may be heated to 1300 F. without coagulation, when it will be found to contain nearly 50 per cent of the meat albumin (Parkes) (See Receipts for Beef Tea).
Experiments on Losses in Cooking Meat, conducted in 1903 by H. S. Grindley and Timothy Mojonnier, at the University of Illinois, led to the following very practical conclusions:
"1. The chief loss in weight during the boiling, sauteing, and panbroiling of meats is due to water removed by the heat of cooking. In the roasting of meats the chief loss is due to the removal of both water and fat.
"2. The losses of nutritive material in the panbroiling of meats are very small as compared with the losses which take place in boiling, roasting, and sauteing.
"3. When beef was cooked in water in these experiments, 3.25 to 12.67 Per cent of the nitrogenous matter, 0.60 to 37.40 per cent of the fat, and 20.04 to 67.39 per cent of the mineral matter of the original uncooked meat were found in the broth. The nutritive material thus removed has been designated as a loss, but is not an actual loss if the broth is utilised for soup or in other ways.
" 4. The experiments here reported show that when meat is sauteed 2.15 per cent of the nitrogenous matter and 3.07 per cent of the ash occurring in the uncooked meat were taken up on an average by the fat in which the meat was cooked, while the cooked meat contained 2.3 times more fat than before cooking.
"5. When the meats were roasted, 0.25 to 4.55 per cent of the nitrogenous matter, 4.53 to 57.49 per cent of the fat, and 2.47 to 27.18 per cent of the mineral matter present in the uncooked meat were found in the drippings.
"6. Beef which has been used for the preparation of beef tea or broth has lost comparatively little in nutritive value, though much of the flavouring material has been removed.
"7. In the boiling of meats, the fatter kinds and cuts, other things being the same, lost less water, nitrogenous and mineral matter, but more fat than the leaner kinds and cuts.
"8. In cooking meats by boiling, sauteing, panbroiling, and roasting, the losses increased in proportion to the degree of cooking. In other words, the longer the time and the higher the temperature of cooking, other things being the same, the greater the losses resulting.
"9. As a rule, the larger the piece of meat cooked by the methods of boiling and roasting, the smaller were the relative losses.
"10. The experiments indicate plainly that different cuts of the same kind of meat behave very differently as regards the amount and nature of the losses which they undergo when cooked in hot water.
"II, Thorough investigation confirms the conclusion that when meat is cooked in water at 8o° to 85° C, placing the meat in hot or cold water at the start has little effect on the amount of material found in the broth".