106 BULLETIN 77, HAWAII EXPERIMENT STATION 



acid as determined by titration against standard alkali using phenol- 

 phthalein as indicator. It is expressed as anhydrous citric acid and is 

 calculated as a percentage of the fresh edible material. 



Water 



The loss in weight of the edible portion of the fruit after drying is 

 called the water content, or moisture content, of the fruit. This is ex- 

 pressed as percentage of the edible portion. A modification of the 

 method of the Association of Official Agricultural Chemists was adopted. 

 A thin layer of fresh, edible material was weighed in a small, shallow 

 weighing bottle, (30 by 45 mm.). Since fruits usually contain appre- 

 ciable amounts of sugars which are lost at a temperature approaching 

 100° C, the samples were dried at a temperature of 65° C. for a period 

 of three days. This was low enough to prevent any but the slightest 

 charring of the sugars and at the same time to dry the sample thor- 

 oughly. The final traces of moisture were removed by leaving the 

 samples in vacuo over sulphuric acid for three days. 



Protein 

 (Nitrogen x 6.25) 



The protein content of the fruit was calculated as nitrogen x 6.25, 

 estimating that all of the nitrogen of the fruit is protein nitrogen and 

 that it constitutes 16 percent of the protein. The nitrogen was deter- 

 mined by the Gunning modification of the Kjeldahl method. 



Ether extract 



The ether extract represents that portion of the fruit which is soluble 

 in ethyl ether (CP. anhydrous, distilled over sodium). In many tables 

 this is classed as fat ; but because it includes other substances such as 

 waxes, resins and plant pigments, and because in most fruits the per- 

 centage is very small, it is probably better called ether extract. 



Crude fiber 



The crude fiber of the fruit represents that portion of the fruit 

 which remains after extraction of the dried material with ether, and 

 after boiling with dilute sulphuric acid and then with dilute sodium 

 hydroxide, but which is lost on ignition. It is considered to be that 

 portion which is not utilized during digestion. 



Carbohydrate by difference 



The carbohydrate figures given in Table 2 represent all carbo- 

 hydrates except crude fiber. These include polysaccharides and all 

 sugars, some of which may not be utilized in the body. The figures 

 were obtained by subtracting the sum of the percentages of water, pro- 

 tein, ether extract, crude fiber and ash from 100. This method of 

 determining carbohydrates involves an error, the greatness of which 

 depends upon the quantity of other undetermined substances, such as 

 pectins, pentosans and organic acids that may be present. 



