200 



Journal of Agricultural Research 



Vol. Ill, No. 3 



The analytical data are given in Table V. The study of the detached 

 fruit permitted a longer period of observation than when bananas 

 attached to the stem were used. The rate of transformation of starch 

 into soluble carbohydrates was very rapid at first — 32.11 gm. per kg. 

 per day. It then increased to 34.9 gm. per kg. per day. Starch hydrol- 

 ysis, so far as revealed by analysis, nearly ceased six days before the 

 end of the life history of the bananas. The analytical data confirm the 

 facts developed in the earlier experiments. 



DISCUSSION OF RESULTS 



As the result of the foregoing studies, the author is in a position to 

 state more exactly than has heretofore been possible the nature and 

 extent of the changes in the composition of bananas during ripening. 

 The most conspicuous change is the long-recognized conversion of starch 

 into sugars. It is most rapid while the fruits are turning from green to 

 yellow. During this period the respiration rate increases manyiold, 

 becoming greatest at the time when the rate of starch hydrolysis is most 

 rapid. Starch hydrolysis then gradually slackens, later ceasing alto- 

 gether. The respiration rate, too, becomes slower, but still remains far 

 more active than in the green fruit. Next to the starch and respiration 

 changes, most conspicuous are those of water. The peel loses, while 

 the pulp gains water steadily. The respective losses and gains in water 

 of the peel and the pulp on ripening, expressed in terms of the original 

 green bananas, are summarized in Table VII. 



Table VII. — Percentage of losses and gains in water 0/ peel and pulp of bananas on 



ripening 



Experi- 

 ment 



No. 



Place of ripening. 



Calorimeter 



do 



Humidity chamber. 



.do.. 



Loss of 



water in 



peel. 



Actual 



gain of 



water in 



pulp. 



I. 64 

 3.02 

 3-52 

 3-94 

 4- 51 

 4-63 

 6.34 



Gain of water 

 in pulp cor- 

 rected for water 

 formed and 

 absorbed in 

 physiological 

 processes. 



2.4 



3-5 



6- 13s 



In the first, second, and fourth experiments it is possible to show how 

 much water is formed or absorbed by the pulp in physiological processes. 

 The water formed in respiration can easily be calculated if formed in 

 consequence of the complete combustion of carbohydrates and if the 

 amount of carbon dioxid evolved on ripening in consequence of this com- 

 bustion is known. The respiratory quotient and the thermal quo- 

 tient determined by the Office of Nutrition Investigations for ripening 

 bananas X16) agree in showing that the carbon dioxid evolved on normal 

 ripening is due solely to the complete combustion of carbohydrates. 



