Oct. 29, 1921 Physiological Study of Grapefruit Ripening 265 



of acid. In the fifth, pick from both trees there is no decided variation 

 in the acid content of the pulp during storage, and the percentage of 

 acid in the juice does not change as much as in fruit from any of the other 

 four picks. With the sugars, the percentage of reducing sugars and of 

 total sugars is always greater at the end of two months in warm storage, 

 except in the fifth pick. The reducing sugar increases most, due prob- 

 ably to the inversion of some of the cane sugar which is less in all cases 

 after two months in storage. 



It was brought out in the earlier publication on grapefruit storage 

 that there was an indication that the acid content of the fruit was slightly 

 increased during a long period of warm storage. It was pointed out 

 also that definite evidence on this point was difficult to obtain because 

 the structure of the fruit prevented accurate calculation of the shrinkage 

 of the various portions. Further evidence, mostly of an indirect nature, 

 may be derived from the data on sugar and acid content of the fruit, 

 found in Tables I and II. As was mentioned above, there is in all cases 

 an apparent increase in the acid content and the total sugar content of 

 the pulp, due for the most part undoubtedly to loss of water during 

 storage. In the tables it is noticeable that the solids-acid ratio is usually 

 less after two months in storage. This indicates, of course, that the 

 increase in soluble solids is not proportional to the increase in acidity 

 and that some soluble substance or substances other than titratable 

 acids decreased in the storage period. This occurs in five cases out of 

 seven on which data were obtained. The other two cases, tree 2, third 

 pick and fifth pick, show slight increases, 0.07 and o. 1 1 , respectively. 



These data are corroborated in the total sugars-acid ratios, which are 

 calculated by dividing the percentage of total sugar as dextrose by the 

 percentage of acid as citric. In the 10 cases the ratio of sugar to acid 

 is less in 7, practically the same in 2, and greater in i. Indications 

 are, then, that there is usually an increase in the ratio of sugar to acid 

 under the conditions of the experiment. This could be brought about 

 by either decreasing the sugar content of the fruit or by increasing the 

 acid content or by a combination of these two factors. It is notice- 

 able that in 6 cases out of 10 the acid-sugar ratio is greater after one 

 month in storage than it is after two months at the same temperature. 

 The acid and sugar in the fruit from warm storage will be considered 

 later in comparison with the changes taking place in cold storage. 



There is in most cases not much variation in the percentage of dry 

 matter during storage, though there seems to be a tendency, more 

 marked in some cases than in others, toward an increase. This seems 

 probable, as the shrinkage where determined is from 14.4 to 23.3 per 

 cent for the full two months in storage. The percentage of peel always 

 decreases during storage at this temperature, due to the loss of water and 

 wilting. This is evident in the decrease in thickness of the peel, which is 

 very marked, especially in the earlier picks. 

 65768°— 21 3 



