48 BULLETIX 1406, U. S. DEPARTMENT OF AGBICITLTURE 



the respiration was 7 to 8 times the respiration rate at 32°, whereas 

 at 85° it was more than 10 times the rate at 32°. Comparative 

 softening rates were similar. 



It is apparent that in general there is an approximate agreement 

 between the respiration rate and the rate of softening of the fruit. 

 Between 40° and 60° F. there appears to be a somewhat greater 

 difference in the rate of respiration than in that of softening, but 

 on the whole, within the range of temperatures here studied, there 

 is a sufficiently close agreement between the softening rate and that 

 of respiration to indicate that the softening processes in apples which 

 are apparently associated with changes in the cell-wall materials 

 may be directly associated with the oxidation processes which are 

 measured in respiration studies. 



The respiratory ratio, determined by dividing the volume of car- 

 bon dioxide given off by the volume of oxygen taken up, is indicative 

 of the type of material being oxidized in the fruit. If reducing 

 sugars are being oxidized to carbon dioxide and water, the respira- 

 tory ratio should be 1. and if malic acid is being oxidized the 

 ratio would rise to 1.33. It is apparent that practically all the ratios 

 fall between these two points, indicating that there is an oxidation 

 of both acids and carbohydrates. A ratio of 1.165 indicates equal 

 oxidation of acids and sugars. In the case of Grimes Golden this 

 is about the average at 32° F., but is distinctly above the average 

 at both 40° and 60°, and is somewhat above the average at 85°, thus 

 indicating that there is approximately equal oxidation of acids and 

 sugars at 32°, while at 40° and 60° sugars are mainly oxidizrd. At 

 85° there is a somewhat greater oxidation of acids. The results with 

 the other varieties are similar. At practically all temperatures both 

 acids and sugars are being oxidized, but on the average it would 

 appear that the greatest oxidation of acids occurs at the highest raid 

 lowest temperatures here studied. This is in line with the fact that 

 on the average acids seem to drop off least during ripening at the 

 intermediate temperatures. 



Because of the wide variations which exist, particularly in the 

 acid content of different individual apples, it is difficult to de- 

 termine accurately the decrease in acidity under different storage 

 conditions. The data in Table 4 together with respiratory data 

 indicate that at all temperatures there is a distinct falling off in 

 acidity owing to oxidation in the normal respiration of the fruit. 

 Under c rtain conditions not yet determined the carbon dioxide 

 given off in respiration appears to come largely from the oxidation 

 of acids. Under other conditions there is relatively little decrease 

 in acidity, and the products of respiration appear to come largely 

 from sugars. In general, there is a fairly close correlation b tween 

 the rate of respiration as measured by carbon dioxide given off 

 and the rate of softening of the fruit. Apparently both the rate of 

 softening and the rate of respiration are controlled almost entirely 

 by the temperature at which the fruit is held. 



SUMMARY OF PART II 



The ripening processes following jDicking are largely a continua- 

 tion of those going on before the fruit is removed from the tree. 



