Dec. i, 1920 Some Changes in Florida Grapefruit in Storage 361 



The structure of citrus fruit makes the study of the physiological 

 changes taking place in it rather difficult. Considering the peel, pulp, 

 and seeds of the fruit, there are then three structures which have very 

 different water contents and water-holding powers. It is impossible to 

 grind the entire fruit and weigh out comparable samples. It would be 

 impossible to slice the fruit and expect the various slices to be compar- 

 able because of loss of juice from the pulp in slicing and the fact that the 

 seeds are not necessarily evenly distributed. If fruits are sliced and 

 the seeds removed, the operation is liable to be attended with a con- 

 siderable loss of juice. After a number of experiments, the following 

 method of sampling was decided upon. After the fruit was weighed it 

 was peeled by making two cuts through the skin completely around the 

 fruit, the cuts crossing each other at right angles at the stem and blossom 

 ends. The peel was removed, and the thickness of each quarter was 

 measured midway along the side by means of callipers. Such por- 

 tions of the rag as adhered to the fruit were removed, and the fruit was 

 weighed again. The percentage of peel was calculated from the weights 

 before and after peeling. The fruit was divided into segments, and the 

 seeds were removed, care being taken that no appreciable amount of 

 juice was lost. Duplicate samples were made from segments from 

 opposite sides of the fruits. One segment from each of the 10 fruits was 

 used for each sample. While this method is not the most accurate, the 

 results of analyses of duplicate samples indicate that it is sufficiently 

 accurate for the work. It must always be taken into account that no 

 two grapefruits have precisely the same chemical composition and that 

 while in this work lots of 10 fruits were commonly used in each set of 

 analyses, some variation will occur between any two lots no matter how 

 carefully the fruits are selected. 



In preparing the samples for analysis, the samples for sugar deter- 

 minations were placed in beakers and covered with 95 per cent alcohol. 

 A few drops of ammonia were added to neutralize the acidity, and the 

 sample was brought to a boil. It was then transferred to extraction 

 thimbles, the alcohol extract was separated at the same time by filtra- 

 tion, and the residue was subjected to continuous extraction for about 

 14 hours with alcohol in a soxhlet apparatus. The extract was added to 

 the filtrate, the whole was made up to 1 ,000 cc. in a volumetric flask, and 

 two 50-cc. aliquots were pipetted off for analysis. Sugar determinations 

 were made according to the method already described. 



For the acid determinations, the pulp was brought to a boil in water 

 and was placed in liter volumetric flasks under toluol and allowed to 

 stand with frequent shakings for about 10 days. It was then strained 

 through linen, and two aliquots were titrated against sodium hydroxid, 

 using phenolphthalein as an indicator. The dry-weight determinations 

 were made by covering the samples with 95 per cent alcohol, driving off 



