60 The Philippine Journal of Science wis 



palatable. The solid portion comprises the usual cellulose plant 

 structure. Fruits also contain a group of substances called pectin 

 and pectose, the exact nature of which has not been definitely 

 determined. The latter gives to unripe fruits their character- 

 istic hardness and indigestibility. During the course of ripen- 

 ing, insoluble pectose is gradually transformed into soluble pectin, 

 a carbohydrate related to starch and sugar. Pectin gelatinizes 

 upon boiling, and fruit rich in this peculiar class of compounds 

 may be utilized in making jelly, as 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. The high water content, with corre- 

 spondingly low percentages of proteins, carbohydrates, and fats, 

 indicates a much less important place for fruits in a dietary 

 than they actually deserve. A relatively high amount of iron is 

 present in almost all varieties and may thus be added to the 

 diet without replacing staple articles of food. It must also be 

 remembered that fruits supply bulk and exert a beneficial laxa- 

 tive tendency. These properties are all of value in opposing the 

 conditions favorable to excessive intestinal putrefaction. In 

 warm climates especially, sound ripe fruit should form a part of 

 the daily food of the people. 



METHODS OF ANALYSIS 



The methods of analysis are of great importance in dealing 

 with complex material such as fruits, and without information 

 on the procedure followed the data obtained are often of little 

 value. For the purposes of this investigation, in every case not 

 specified, ripe fruits in sound condition were studied. 



The edible and waste portions were carefully separated, and 

 the former passed through a meat grinder until uniform repre- 

 sentative samples could be obtained. The determination of total 

 solids was carried out by drying, first on a steam bath, then 

 to constant weight at 80 °C. 



Insoluble solids were determined by repeated extraction with 

 warm water of 20-gram samples on a folded filter and drying 

 the resulting solid at 80°C. The combined filtrates were titrated 

 with tenth normal alkali using phenolphthalein as indicator, 

 since this gives the most accurate total acidity. This value is 

 expressed in terms of the acid actually present, and also as sul- 

 phuric acid for purposes of comparison. The fruit acids were 



