Oct. 29, 1921 Physiological Study of Grapefruit Ripening 273 



The total sugar content is usually slightly higher at the end of the four 

 months' storage period, though there are several instances in which it is 

 lower. These cases are mostly in well-matured fruit of the last pick. 

 The increase in total sugars is due for the most part to an increase in 

 the reducing-sugar content, as there is usually a marked decrease in the 

 percentage of cane sugar during storage. There is never more than 5 per 

 cent shrinkage during these four months. This shrinkage is doubtless 

 partly from the peel and partly from the interior portion or pulp. 



The fact that in most cases there is an apparent increase in total sugars 

 can be accounted for by the loss of water and consequent shrinkage. It 

 is very evident from these data that there is no appreciable diminution 

 in the amount of sugar in the grapefruits in four months at 32° F. On 

 the other hand, there is without doubt no considerable increase. It is, 

 of course, probable that some of the pectins and other hemicelluloses or 

 the glucosid in the fruit break down slowly, and it is possible that some 

 reducing substance is formed from these decomposition products. 



A comparison of the behavior of the acids and sugars in grapefruits 

 stored in warm storage (Tables I and II) with the results obtained in the 

 cold storage experiments just considered brings out some rather striking 

 differences. In the data obtained from the warm storage experiments 

 there is evidence of an increase in acidity or a decrease in total sugars or 

 both — that is, in most cases the ratio of total sugar to acid decreases, while 

 in the cold storage the reverse is true. This is corroborated by the acidity 

 and soluble solids of the juice. In the warm storage experiments the 

 solids-acid ratio is in most cases less after two months in storage, while in 

 the cold storage there is always a decrease in acidity and an increase in 

 solids-acid ratio. It is evident that there is an increase, or at least not 

 a decrease, in acidity in warm storage and a decided decrease in cold stor- 

 age. It would, therefore, seem probable that some of the processes which 

 go on in the fruit stored in the warm are modified when the fruit is placed 

 in cold storage. It is possible, of course, that in respiration the acid is 

 used up in cold storage while the sugars are used in warm storage. There 

 is an indication that the sugar content may decrease slightly in the fruits 

 held in warm storage, while there is no evidence of change in the per- 

 centage of sugar in the cold-stored fruits. Magness (9) has shown that the 

 composition of the gases in the interior of apples and potatoes varies 

 with the temperature at which they are held. For example, he found 

 that the gas from the interior of Yellow Newtown apples stored at 2° C. 

 (about 35° F.) analyzed 14.2 per cent O2 and 6.7 per cent CO2, while at 

 30° C. (86° F.) the extracted gas was 3.2 per cent O2 and 21.4 per cent 

 COj. The air surrounding the fruits used in these experiments was practi- 

 cally the same in both cases. The oxygen content was low and the carbon- 

 dioxid content high in the fruit at high temperatures because the oxygen 

 was used up in respiration faster than it could diffuse in from the outside. 

 While no such determinations have been made on grapefruits, it seems 



