32 CHEMICAL COMPOSITION OF SOME TROPICAL FRUITS. 



determined by Meissl's method for invert sugar, and cane sugar was 

 determined both by the increase in reduction after inversion with 

 hydrochloric acid and by double polarization. The polarimetric 

 method used was that of the German official chemists, and cane sugar 

 was calculated by the Herzfeld formula: 



100 (A-B) 



S= 



UL89+0.05B 



Results by the two methods agreed very closely, especially where the 

 amount of cane sugar was small. With samples of high content of 

 cane sugar, the results by the reduction method were less reliable, 

 owing to the influence of the cane sugar upon the reduction. 



While the acids of pineapples are largely citric they are expressed 

 in this paper as sulphuric acid for the purpose of comparison. 



ANALYTICAL DATA. 



Table XI contains the results of analysis of the fresh pineapples. 

 As will be seen by reference to this table, there is no material differ- 

 ence in composition due to the source of the pineapples; neither does 

 the variety seem to have any influence on the composition. Insoluble 

 solids, ash, acids, and protein do not show a wide variation, while on 

 the other hand the samples show a wide difference in the content of 

 sugars. As is well known, the sugars develop very rapidly with the 

 ripening of the fruit, but the other constituents appear to be present in 

 equally large amounts in the green fruit. Of particular interest are 

 the relative amounts of reducing and cane sugars in the fresh fruit. 

 In nearly all cases the cane sugar is largely in excess of the reducing 

 sugar. The average amount of reducing sugar in all the samples of 

 fresh fruit is 3.91 per cent, while the average amount of cane sugar is 

 7.59 per cent, nearly double the amount of reducing sugar. 



Table XII contains the results of analysis of the pineapples canned 

 under direction of the consuls-general at Singapore and Nassau. The 

 samples put up without addition of cane sugar were preserved in 

 expressed pineapple juice, the amount of juice added being about 30 

 per cent of the entire contents of the can. As far as content of total 

 sugars is concerned, therefore, the composition of these canned pine- 

 apples should not be materially different from the composition of the 

 normal fresh fruit. Other constituents, especially insoluble solids, will 

 be lowered by the addition of the juice, as comparison of Tables XI 

 and XII shows. While the amount of total sugar is practically the 

 same as in the fresh fruit, the relative proportions of reducing and 

 cane sugars are entirely different, due to the inverting action of the 

 organic acids during the processes of canning. In many cases the 

 amount of the cane sugar remaining is quite small, the average for all 

 the samples being 3.41 per cent of cane sugar and 7.99 per cent of 

 reducing sugars just the reverse of the condition in the fresh fruit. 

 This condition also holds in the samples put up with addition of cane 

 sugar and with the commercial samples. 



