264 Journal of Agricultural Research voi. xxii. no. s 



METHODS OF ANALYSES 



The fruit was prepared for sampling and sampled as in the previous 

 work. Analyses were made for acids, sugars, both reducing sugars and 

 total sugars, dry weight, shrinkage, thickness of peel, and percentage of 

 peel. In addition the acidity and specific gravity of the expressed juice 

 of the fruits were determined and the solids-acid ratio calculated after the 

 usual method. The acidity determinations were carried out as in the 

 previous work, as were practically all the other determinations with the 

 exception of the extraction of the sugar from the pulp. In the sugar 

 extraction a method was followed similar to that described in work on 

 potatoes (6). The weighed pulp was placed in a liter volumetric flask which 

 was then filled to volume with 85 per cent alcohol. It was allowed to 

 stand with frequent shakings for about three weeks, the losses from 

 evaporation, of course, being made up by adding alcohol. The alcoholic 

 solution of sugar was then separated from the residue by filtration, and 

 the sugars were determined in aliquots of the filtrate. 



The first lot of grapefruit was of small size, green in color, with very 

 little juice in the pulp. No solids-acid determinations were made on 

 this lot. They were, however, maintained in warm storage for two 

 months. At the end of this period many of them had assumed the char- 

 acteristic yellow color of the ripe grapefruit. 



The second pick, received August 29, was much further advanced, 

 being about 50 per cent colored and of good size. The third and fourth 

 picks, those of October 25 and November 28, respectively, were in fine 

 condition for shipping and are what would be considered midseason 

 fruit. The November 28 fruit was fair, possibly a little coarser than 

 the two picks immediately preceding. No sprouted seeds were found 

 in any of the fruits, however. The date of picking might be considered 

 as in the latter part of the grapefruit season for this locality and for this 

 variety. 



The analyses of grapefruit picked from trees i and 2, from warm 

 storage at about 70° F. for one and two months, are shown in Tables I 

 and II. In the analytical work the analyses were usually made in 

 duplicate, and both analyses are given in the tables, as this furnishes 

 evidence on the experimental error in the method of sampling. The 

 tables are self-explanatory. 



An inspection of Tables I and II shows that in the first four pickings 

 there is in all cases an increase in the acid content of the pulp, while in 

 the last picking from both trees there is no decided increase. A com- 

 parison of the acid content, as determined in the analyses of the 

 pulp and the acid content of juice, shows a similar behavior. The acid 

 content of the juice is, as a rule, markedly higher than that of the pulp, 

 due, of course, to the fact that in the last-mentioned case the weight of 

 fibrous material is taken into consideration in calculating the percentage 



