THE MONTHLY BULLETIN. 



CALIFORNIA STATE COMMISSION OF HORTICULTURE 

 Vol. V. December, 1916. No. 12 



PRELIMINARY OBSERVATIONS ON THE RIPENING OF 



BARTLETT PEARS. 



By W. V. Cruess and P. M. Stone, Zymology Laboratory, University of California, 



Experiment Station, Berkeley. 



Bartlett pears for shipment to Eastern markets are picked while still 

 hard and green in order that they will not spoil in transit. The pears, 

 ii" not picked too soon, ripen satisfactorily en route or after reaching 

 their destination. There is, however, a minimum degree of ripeness 

 below which the pears will not mature properly. In cooperation with 

 the State Horticultural Commission, preliminary tests were made 

 during the past season to ascertain if a simple chemical test could be 

 used to determine when the fruit is ripe enough for shipping purposes. 

 Unfortunately, the experiment was not started early enough in the 

 season to obtain the results desired, but the data accumulated seem of 

 sufficient interest to justify publication. In carrying out the tests 

 during another season, the samples should be taken at least four to 

 six weeks earlier than was the case during the past season. 



PLAN. 



One box samples of Bartlett pears were taken during the shipping 

 season under the direction of the State Horticultural Commission in 

 Sacramento, Placer and Contra Costa counties. These were shipped to 

 the Zymology Laboratory and held at 20 degrees Centigrade or 6S 

 degrees Fahrenheit until ripe. In addition to this routine method 

 of ripening, a few lots were ripened under special conditions, some 

 being placed in a refrigerator, some in an atmosphere of carbon dioxide, 

 and others in a dessicator; the effects of temperature, carbon dioxide, 

 and lack of air, respectively, upon the manner and rapidity of ripening 

 being observed. Disappearance of starch was noted by halving the 

 pears horizontals and longitudinally and applying a weak solution of 

 iodin to the cut surface. As soon as the pears were received, the 

 specific gravity and acid of the juice were obtained for comparison 

 with similar data to be taken on the ripe and overripe pear juice later. 

 Samples of the pulp of the green and ripe fruit were retained for 

 further observation in respect to starch, sugar, and acid. The color, 

 average size, and weight of the pears from each box were also noted. 



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