The chemistry of plant and animal life . pureprotein is one. The albumin of eggs and milk and thegluten of grains are types ofpure proteids. In many foods,as potatoes, roots, and fruits,less than half of the crude pro-tein is pure protein. Crude pro-tein, from different sources, isunlike in character, composition,and, to a certain extent, in foodvalue. Less is known of itscomposition and food value thanof any other class of nutrientsin foods. In the analysis of plant andanimal substances, the chemistfirst determines the per cent, oftotal organic nitrogen and thenmultiplies this by to obta
The chemistry of plant and animal life . pureprotein is one. The albumin of eggs and milk and thegluten of grains are types ofpure proteids. In many foods,as potatoes, roots, and fruits,less than half of the crude pro-tein is pure protein. Crude pro-tein, from different sources, isunlike in character, composition,and, to a certain extent, in foodvalue. Less is known of itscomposition and food value thanof any other class of nutrientsin foods. In the analysis of plant andanimal substances, the chemistfirst determines the per cent, oftotal organic nitrogen and thenmultiplies this by to obtainthe equivalent amount of crudeprotein. This is because theproteids contain, on the average, 16 per cent, nitrogen, or there is about one part ofnitrogen to every of protein (100 h-16 ^ ).The nitrogen can be determined with accuracy ; in fact,the method for its determination is one of the most accu-rate in chemistry. In brief, the method consists in firstdigesting a small weighed amount of material in a flask 15. Fig. 81.—Digestion apparatusused in the determination of 226 AGRICULTURAI, CHEMISTRY with sulfuric acid to oxidize the organic matter and con-vert the nitrogen into ammonium sulfate (see Fig. 8i).
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