172 COLLOIDS IN BIOLOGY AND MEDICINE 



Naturally a salt solution of the same concentration (5-10 per cent) 

 is always employed. In pure water, shrinking occurs immediately, 

 since muscle albumin coagulates in it spontaneously. High concen- 

 trations of salt, 25-30 per cent, likewise depress the curve. 



New problems arise in cooking meat. If meat is boiled in pure 

 water we obtain a "weak" broth. Muscle albumin coagulates in 

 water before heat coagulation occurs and this impedes the exit of the 

 crystalloid. Salt is therefore added immediately if good soup is to 

 be expected. With boiling, heat coagulation occurs whereby the 

 meat loses from 20 to 30 per cent of its water. The mechanism of 

 this loss is still unknown. We can understand why there should be 

 a loss of from 20 to 35 per cent in roasting, and it would be still 

 greater if the surface were not constantly protected by pouring over 

 or dipping into fat (basting). 



Preserved meats are less perishable because they contain less water 

 and because the muscle albumin has been converted into a character- 

 istic gel condition. This end is attained in various ways: In pick- 

 ling, water is removed from the meat by the salts of the brine, 

 while at the same time there is an exchange of crystalloids, whereby 

 salts enter from without which change the albumin as regards its 

 'coagulability and swelling capacity; and extractives leave it and 

 are removed with the brine. Of course very important changes 

 occur during storage, so that according to A. GARTNER, with in- 

 creasing age pickled meat becomes more difficult of digestion and 

 loses 30 per cent of its nutritive value. Smoking of meat is usually 

 preceded, by a short pickling process. The abstraction of water in 

 this case is accomplished by means of a strong current of air, and in 

 the dried meat (pemmican) which is much relished in some regions, in 

 the Arctics (for instance) , there is no loss other than water. 



Naturally, the properties of every gel, materially, depend upon its 

 history. To quote a single example: F. STOFFEL* (in the laboratory 

 of PROF. H. ZANGGER) found, that the diffusibility of one and the 

 same substance through the identical gelatin differed, depending 

 upon whether the gelatin was rapidly solidified with ice or slowly 

 cooled at room temperature. Accordingly, we may assume in the 

 case of meat, that the properties of the coagulated albumin will vary 

 with the conditions maintained during coagulation, and that upon 

 these depends its food value. 



An essential question in the investigation of sound meat, pre- 

 served meats and food preparations must be their available food 

 value, which can be answered only by complicated and expensive 

 metabolism investigations. From my point of view this ought to 

 be a fruitful field for the colloid chemist, who ought certainly to be 



