APPLES AS FOOD 13 



Protein 



The apple contains a somewhat smaller percentage of protein than many of the 

 other fruits. The proximate composition of the apple shows 0.3 percent of pro- 

 tein as compared with 0.6 percent in blueberries, 0.6 percent in cantaloupes, 0.5 

 percent in watermelon, 0.4 percent in pineapple (Sherman, 1946). 



The few available studies on the amino-acids of the protein of apples indicate 

 that it is composed mainly of arginine, histidine, and lysine, all of which belong 

 to the group of "essential amino-acids," indispensable in mammalian nutrition. 

 The proportion of the amino-acids remains fairly constant during the develop- 

 ment of the apple. The amide nitrogen forms 24.8 percent, the amino-nitrogen 

 45.3 percent; the "rest" nitrogen, including imino-nitrogen, 20 percent; nitrogen 

 formed from NH3 6.3 percent; and basic nitrogen 3.6 percent (Hulme, 1936). 

 Research on the nature of the protein of the apple is now in progress in this de- 

 partment. 



Flavor 



Shaw (1911) stated that the characteristic flavor and aroma of apples is due 

 to certain esters or flavoring oils which are of great importance in determining 

 the quality and value of the apple. Power and Chestnut (1920) analyzed the 

 odorous constituents of several varieties of apples and found them to consist 

 essentially of the amyl esters, acetic and caporic acids, with a very small amount 

 of caprylate and a considerable portion of acetaldehj'de. The essential oil 

 possessed to a high degree the characteristic fragrant odor of fresh apples. The 

 yield of oil from the peel of Ben Davis apples was 0.0035 percent and from that 

 of crab apples 0.0043 percent, corresponding to about 0.0007 and 0.0013 percent, 

 respectively, of the entire ripe fruit. In an examination of Mcintosh apples, 

 Power and Chestnut (1922) confirmed the results of their earlier investigations 

 that the odorous constituents of the apple consist chiefly of amyl esters, and ob- 

 tained further information respecting the substance that imparts a distinctly 

 roselike odor to some apples. This substance, present in minute amounts, was 

 found to be geraniol. 



More recently Milleville and Eskew (1944) have described a commercial method 

 for the recoverj^ and utilization of nature. 1 apple flavors. The product is a color- 

 less water solution of the volatile constituents of natural apple flavor concen- 

 trated from 100 to 150 fold. The actual proportion of flavoring constituents in 

 the solution does not exceed a few tenths of one percent by weight. The odor of 

 the concentrate was mildly pungent and no perceptible changes have been found 

 to occur in the product during storage. 



Oils and Waxes 



Oils and waxes exist in the apple, particularly in the peel, in very small quan- 

 tities. Sando (1923) investigated the constituents of the waxlike coating on the 

 peel of the apple and isolated triacontane (C3oH62)i heptacosanol (C27H56O), 

 and an alcohol, malol (C30H48O3), as well as several other fractions apparently 

 consisting of mixtures of hydrocarbons and alcohols. In further work Markley 

 and Sando (1931) found that ursolic acid (a monohydroxytriterpene acid), oil 

 fraction, and total ether extract in the peel of apples increased throughout the 

 growing period and during storage. Larger quantities of ursolic acid and total 



