Aug. i6, 1920 Ripening and Storage of Bartlett Pears 493 



In the latest picked lots from all sections the acid was very nearly the 

 same, both in the green fruit and in the ripened fruit, regardless of the 

 temperature of storage used. The acid content seems to become more 

 nearly stabilized in the late season. It will be noted, however, that 

 whereas the acid content in the California pears was very low at this 

 time, in the fruit from the northern regions it was higher than at any 

 other time during the season. 



The question as to why the acid content should remain more nearly 

 constant in late-picked than in early picked fruit is naturally suggested 

 by these results, but until something more is known of the synthesis of 

 the acids and the r61e they play in fruit and plant respiration a solution 

 seems improbable. 



ALCOHOL-INSOIvUBIvE, ACID-HYDROLYZABLE; REDUCING SUBSTANCES 



Results of analyses made as these were, by hydrolyzing the residue 

 from an alcohol extraction with dilute acid and determining the reducing 

 substances present, have usually been reported as starch. That this may 

 be very misleading is showTi by the fact that ripe pears contain no starch, 

 as proved by iodin tests, yet the residue from the alcohol extraction after 

 being hydrolized contained a considerable amount of reducing material. 

 It is almost certain that an equal or even greater amount of such 

 material found in the green fruit is also made up of substances other 

 than starch. For this reason the percentage weight of this group of 

 substances has been figured as dextrose, and the figure includes starch, 

 together with certain hemicelluloses, galactans, pectin materials, etc., 

 which may be present in varying amounts. 



A study of the data presented in Tables I to IV shows that these 

 reducing substances run highest in the earliest lots when first picked from 

 the tree. There is a decreasing amount in the green fruit at successive 

 pickings, until the last lots contain only about two-thirds as high a 

 percentage of these substances as do the earliest pickings. 



There is a very marked drop in the amount of alcohol-insoluble, acid- 

 hydrolyzable reducing substances present in the storage-ripe fruit as 

 compared to the similar lots when picked. Compare column 15, green, 

 with columns 16 and 18, ripe. This, of course, is natural, since all the 

 starch and probably some of the other material have disappeared. It is 

 interesting to note, however, that there is also a decrease in the amount 

 of these reducing substances in the ripe fruit from late pickings as com- 

 pared to ripe fruit from early pickings. This decrease in many cases 

 amounts to 50 per cent of the total and seems to indicate that 

 as the fruit develops on the tree much material other than starch 

 changes over to sugar or is in condition to change over after picking. 



These results are interesting when considered in connection with the 

 findings of Lewis, Mumeek, and Cate (9) on the decreasing resistance of 



