ON COOKED FOODS 



r,v KATHARINi: I. WILLIAMS, H.Sc. 

 The University, Bristol. 



In this article the question of foods, especially cooked 

 fish, vegetables and cereals is dealt with from the 

 chemical point of view. 



For many years the author has been engaged upon 

 the investigation of the chemical composition of 

 such food materials, and the suggestion has been 

 made that the general public, and not onl\- the 

 chemical world, might be interested in this import- 

 ant subject. In America the question is brought 

 before the public to a much greater extent than it is 

 in England : a great deal of valuable information has 

 been published there. Congress has granted money 

 to the Department of Agriculture, bulletins on the 

 subject are distributed freely, and several of the so- 

 called Farmers' Bulletins deal with the uses of milk, 

 fish, eggs and other ordinary kinds of nourishment. 



It is hardlv necessarv to state that to be of real 

 value all such investigations must be quantitative : 

 that is, must show in percentages the amounts of 

 the various constituents present. The first recorded 

 quantitative analvsis of any food was made in this 

 country bv George Pearson in 1795, who determined 

 the proportion of water, starch, ash, fibre and 

 extractive matter in kidney potatoes. For about 

 eighty-five vears similar work was carried on in 

 Europe, chiefly in Germany. Since then many 

 American chemists have devoted themselves to this 

 subject. Bulletin No. 28 (Office of Experiment 

 Stations. Department of .\griculture). prepared by 

 Professor .Atwater and .A. P. Bryant, entitled " The 

 Chemical Composition of .\merican Food Materials." 

 contains details of the analyses of four thousand and 

 sixty .\merican articles and commodities used for 

 human food in that countr\-, but in most cases the 

 food is uncooked. 



During the last few years Professor Grindley, in 

 the University of Illinois, and others have devoted 

 themselves to the study of the effect of various 

 methods of cooking meats. 



It is well to understand what is meant by food, 

 and the definition given bv Dr. R. Hutchinson in 

 " Food and the Principles of Dietetics" is perhaps 

 the simplest that can be given — "anything which, 

 when taken into the body, is capable of either 

 repairing its waste or of furnishing it with material 

 from which to produce heat or nervous and muscular 

 work." Other substances mav have a useful place 

 in our dietary, though not falling into the category of 

 food-stuffs. Later on it will be seen how various 

 commodities answer to this description. The 

 ordinar\- articles of diet are mixtures of various 

 chemical substances, some of which are of value as 

 nutrients, others are not. Of the former the most 

 important are the nitrogenous ; as the name implies 



they all contain nitrogen. They are known under 

 various names: gluten in l)read, legumin in the 

 pulses, but are common!}' spoken of as the proteins. 



Non-nitrogenous is a general name for the carbo- 

 hydrates, starch, sugar, and so on, also the fats, such 

 as butter. Table salt and other mineral matters, and 

 water, are also of importance : the latter is not onl}- 

 contained in the liquids we drink, but also forms 

 part of the solids we eat. 



The main object of the investigations now to be 

 considered was to arrive at a clear idea of the value 

 of foods as served at table, and the results show 

 that manv wrong impressions exist as to the pro- 

 portion of nutrients the}' contain. 



In commencing the study of a food, the first stage 

 is to weigh the sample; then, if it is fish, it must be 

 cleaned, the scales scraped off, the refuse weighed : 

 with such vegetables as cabbage and broccoli the 

 outer leaves must be removed: the pods of peas and 

 beans all come under the head of refuse: the pods, 

 however, have a value for soup. With potatoes the 

 skins should not be removed before boiling, as valu- 

 able salts are mainh- found in the la}er just under 

 the peel. 



The sample is again weighed, and cooked, and is 

 then in the condition in which it would be served at 

 table. It is then re-weighed to ascertain the increase 

 or decrease in the amount of water gained or lost. 



.\11 waste is removed, such, for instance, as the 

 bones and head of fish, the hard part of asparagus. 

 With cereal foods, on the other hand, there is no 

 refuse. 



Rei'lise .\s served at Table. 



We now pass to the main question, what is the 

 value of the edible portion of the various cooked 

 foods ? .\nd the first point to consider is the 

 amount of water, which is most important, as we 

 could not live on drv foods; but, on the other hand, 



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