276 



THE AGRICULTURAL NEWS. 



August 30, 1913 



FRUITS AND FRUIT TREES. 



THE COMPOSITION OP TROPICAL FRUITS. 



With the exception of the few data available concerning 

 citrus fruits, the banana, and the pineapple, practically no 

 systematic work has in the past been earned out in studying 

 the chemical composition of tropical fruits. The usefulness 

 of such work, apart from its scientific interest, is that it 

 enables those fruit growers whe produce high grade or 

 distinctive varieties, to bring the fact before the pulilic in a 

 concrete and irrefutable manner. In other words, it would 

 appear desirable, under certain circumstances, to advertise 

 the fact in the open market in order to create a special 

 demand. 



The paper which serves the basis of the figures given 

 at the end of this article was prepared by D. S. Pratt and 

 J. I del liosario and published in the Philippine Journal of 

 Sciayice for February 1913. Dealing in a general manner 

 with the composition of fruits and their characteristics, the 

 authors point out first of all that the individual odour and 

 taste are dependent upon the presence of traces of 

 compound ethers and esters present in amounts that in 

 most cases preclude identification, but which are very 

 important in making the fruit palatable. I'ruits also contain 

 a group of substances called pectin and pectose, the exact 

 nature of w-hich has not yet been definitely determined. The 

 latter gives to unripe fruits their characteristic hardness and 

 indigestibility. During the course of ri[jening, insoluble 

 pectose is gradually transformed into soluble pectin — a carbo- 

 hydrate related to starch and sugar. I'ectin gelatinizes 

 upon boiling, and fruit, rich in this peculiar class of com- 

 pounds may be utilized for making jelly, since it is upon 

 them that the setting power of the juice depends. 



The nutritive value of fruits lies chiefly in the sugars 

 present, although the acids and salts exercise an important 

 function in the digestive processes. A high water content, 

 with correspondingly low jiercentages of proteins, carbohy- 

 drates, and fats, indicates a much less important place for 

 fruits in a dietary than they actually deserve. For instance, 

 fruits contain a relatively high amount of iron which has 

 a tonic action, and it must also be remembered that fruits 

 supply a bulk and exert a beneficial la.\ative tendency. Iv 

 warm climates, especially, sound ripe fruits should form 

 a part of the daily food of the people. 



The table which follows has been compiled from results 

 given in the publication acknowledged above, and it scrve^: to 

 indicate the dirtereiice in regard to chemical composition 



between the common tropical fruits, which it is feared are 

 frequently hastily consumed in large numbers with little 

 cognizance of the amount of nutriment they contain. 



An apparently satisfactory way of preserving timber is 

 by means of the simple process of charring. According to 

 the GarJcnn-'s Chrunide (July 19, 1913) a practical test has 

 shown the satisfactory nature of this treatment. The 

 charring process is easily and cheaply carried out by lighting 

 a fire of wood and i)lacing over the fiame a portion of each pose 

 which is to be treated. This is done by supporting each end 

 of the post on a large stone or block of wood at the required 

 height. The wood should not be merely surface scorched, 

 but thoroughly burnt to, say, 3 inch in depth. The effect of 

 this treatment is not only to provide an outer protective 

 covering, but also to force the tannin and other products 

 inwards, thus etfcctually sealing up the inner layers of wood 

 and preventing fungus and insect attacks. 



