313 



CHEMISTRY. 



frEEPARAIIOS OF FOOD. 



$ 44. Efftttt ef Cooking. The foregoing description 

 refers to the raw flesh. What becomes of thU when 

 boiled or rovted I If we put a niece of moat into boiling- 

 wator, and leave it long enough exposed to the boiling 

 trmivruturo, the soluble albuminous substances coagu- 

 late- ; tho tihriueis transformed into two new coraponn.K 

 each of which is richer in oxvgen than the fibrine itself, 

 and only one f which resembles fibrine in its difficulty 

 of solution. The other, which may also bo obtained from 

 albumen, is easily dissolved in water. 



The colouring matter of the blood tarns brown from 

 bailiff decomposed at the boiling-point. By this process it 

 also loses its solubility in water. 



The cellular tissues dissolve, as by boiling they are 

 transmuted into gelatine. 



The fatty suUtances melt. Those of the inorganic 

 compounds which are more easily soluble, are dissolved 

 in i ho water. The same takes place with the sugar, the 

 lactic acid, to which the flesh-juice owes its acidity, tho 

 kreatine, flesh-basis, and flesh-acid. 



The albumen being coagulated by the boiling-water in 

 the external parts of the meat, forms around the internal 

 part a cover or outside, penetrable only with difficulty. 

 A large proportion of the soluble alimentary principles is 

 consequently retained, which the water would otherwise 

 have abstracted from the meat. The heat, however, 

 penetrates to the interior ; each flesh-bundle gets sur- 

 rounded, as it were, by a sheath of coagulated albumen. 

 This protects the gelatine and the salts, tho lactic acid 

 and the kreatine, but, most of all, the real flesh-fibre, 

 which, l>y the direct actiou of the boiling-water, would 

 gradually become harder and more tenacious. Accord- 

 ingly, the flesh yields only very little of its constituents 

 to the water, by quick boiling, and preserves with the 

 alimentary principles, not only its nutritivcness, but also 

 its flavour. 



If, therefore, the cook wish to prepare a juicy, savoury, 

 and rich food, she puts the meat into the water raw when 

 the latter is in a state of ebullition ; but if a strong broth 

 is to be prepared, she puta tho meat into cold water, and 

 heats it gradually. The soluble alimentary principles 

 are, by this process, abstracted from tho moat, and dis- 

 solved by the water before the albumen can coagulate. 

 It in true, that when the solution boils, a quantity of 

 small albuminous scales are formed, which are skimmed 

 off with the colouring matter of the blood, which has now 

 turned brown, and other adhering substances. But 

 when the water boils, another part of the albumen is 

 transformed into a combination containing more oxygen, 

 and soluble in water. The same takes place with the 

 fibrine of tho muscles, which comes into direct contact 

 with the lioiling-water. Thus, a solution is formed con- 

 sisting of transformed albuminous substances, kreatine, 

 flesh-basis, and flesh-acids, gelatine and lactic acid, 

 besides some salts ; while small scales of albumen and 

 .1 fats the well-known fat-bubbles float on the 

 liquid in an undissolved state. The broth thus prepared 

 is savoury, but the meat all tho poorer and tougher, in 

 proportion as tho water has been more slowly heated. 



This explains why iu (Jermany, iu the households of 

 tho middle classes, where meat is put on the tire with 

 cold water, boiled meat is seldom or never taken without 

 broth ; for tho boiled meat, and its broth, contain the 

 constituents of the raw meat. In other countries, the 

 Netherlands for instance, boiled meat without broth in 

 very common food. Tho Dutch cooks, therefore, put 

 the meat which has not to furnish any soup, on the fire 

 with boiling-wat 



By roasting, as in the torx?r case, a kind of sheath is 

 formed around the me.it. The albumen coagulates on 

 the external surface, which becomes of a deep brown by 

 the decomposition of tho colouring matter ; and after- 

 wards by the formation of several empyreumatic-smelling 

 substances.' This surface retains the greater proportion 

 of the soluble substances in tho meat, from which a thick 

 substantial juice oozes out in a proportionately scanty 

 quantity ; a part of tho fatty substance is decomposed 

 stearic acid, for instance, being changed into uiargaric 

 acid ; and liiially, an important substance is produced 



namely, acetic acid, which originates in the action of dry 

 heat used in roasting, and facilitates the solution of tho 

 albuminous matters. 



Vinegar has the effect of rendering the meat moro 

 digestible, like common salt, by dissolving the albuminous 

 substances, as has been mentioned in discussing tho 

 process of digestion. ThU is tho explanation of an 

 expression common in Germany that vinegar makes tho 

 meat short ; short meat being easy of digc 



Largo pieces of meat, which after boiling or roasting 

 contain liquid blood in the interior, are, in Germany, 

 sidered not to be sufficiently done; whereas, in En: 

 this is in many cases required as a proof of good cooking. 

 What is the cause of the blood being thus retained ( It 

 is because the colouring matter of tho blood is not de- 

 composed, excepting where the temperature has been 

 increased to more than 158 Fah. The internal parts 

 which retain the crimson hue, have not attained this 

 temperature. 



45. Difference of Taste. Although the difference of 

 taste in different kinds of meat would indicate material 

 distinctions iu their compositions, yet the ascertained 

 differences are very trifling in the case of the flesh < 

 sheep and roe ; these belong, like the ox, to the class of 

 Ruminants, and correspond most exactly with beef in the 

 alimentary principles which they contain. The fat of 

 sheep, however, is generally harder that is to say, richer 

 in stearine ; and the fat of the roe is more ncid than that 

 of beef. 



Pork is richer in fat, but poorer in albuminous sub- 

 stances than beef, although even here the difference is 

 not considerable. 



All wild Mammalia are remarkable beyond our domesti- 

 cated animals for tho quantity of kreatine which they 

 contain ; the latter, however, surpass the former in tli'-ir 

 proportion of fat. The reason of this is obvious. Whilst, 

 iu the ox fattening for food, its even and quiet exi.-' 

 promotes the formation of fat, and moderates the tissue 

 change the roe, leading in the woods a free and active 

 life, takes in a greater quantity of oxygon, which trans- 

 forms tho nitrogenised basis of the t > kreatine. 

 It is the same with birds ; their rapid flight, and their 

 bones filled with air, augment their reception of oxygen. 

 The higher temperature of the bird proves that it con- 

 sumes oxygen faster than the reptiles crawling on the 

 <-urth ; even faster than tho Mammalia, the only class of 

 animals with which it shares tho appellation of warm- 

 blooded. Hence the more rapid decomposition of its 

 albuminous matter, of which the proportion of soluble ' 

 albumen is, besides, greater than in the other Mammalia ; 

 hence, also, the abundance of kreatiue in tho muscles of 

 birds. 



While between the Mammalia and birds, no groat 

 difference has been observed in the amount of water 

 they contain, the three-quarters in weight of water con- 

 tained in the flesh of warm-blooded animals, is increased 

 to four-fifths and more in the flesh of tho fishes. Littlo 

 blood, and therefore mostly a white colour ; much less 

 muscular fibrine; a larger quantity of tissue yielding 

 gelatine; and, above all, a fat containing phosphorus, 

 which is not limited to the contents of the blood-vessels, 

 are regular peculiarities in the flesh of fishes. And this 

 phosphorous fat does not constitute tho only difference in 

 their properties; for the soluble albumen of the lish, 

 which nearly corresponds in quantity with that of the 

 flesh of birds, coagulates much more rapidly in a some- 

 what higher temperature, than the soluble album 

 the warm-blooded animals. The soluble albumen differs 

 also from the latter by not containing any phosphorus. 



40. Comparative Quality's of Fletn We have to take 

 into consideration not alone tho species of the animals 

 whoso muscles furnish our meat, but alto numerous other 

 circumstances affecting tho flesh, before it appears on the 

 table. 



Thus the flesh of young animals is poorer in fibrine 

 than that of tho mature, but richer in soluble albumen, 

 gelatinous fibres, and water : it is therefore more tender. 

 This preponderance of gelatine explains why tin: l<n>th 

 of veal and lamb sooner coagulates than that of beef and 



