FRUIT PRESSURE TESTERS 



17 



Table 5. — Pressure-test limits recommended for picking plum varieties for long- 

 distance shipments 



[Plunger, Me of an 



inch in diameter; penetration, M 6 of an inch] 







Pressure-test limits when shipped 

 standard refrigeration (pounds) 



State 





Variety 



Without precooling 



With precooling 



Litera- 

 ture 

 reference 





Upper 

 limit 



Lower 

 limit 



Upper 

 limit 



Lower 

 limit 





Beauty 



13 

 20 

 18 

 20 

 15 

 16 

 18 

 15 

 13 

 16 

 12 

 15 



9 



14 

 13 

 15 

 11 

 11 

 12 

 12 

 9 

 11 

 8.5 

 12 



8 

 13 

 12 

 14 

 10 

 10 

 12 

 11 



8 

 10 



6 

 8 

 8 

 10 

 8 

 8 

 9 

 8 

 6 

 7 



/California. __ 





"Rnrharik 





Climax 





Diamond.. ■• 





Duarte__ ___ _____ 











Idaho 





Santa Rosa_ 





Wickson 



Formosa _ 





President.. 



(58) 



Do* 







Oregon _ _ _ _ 



(S3) 













1 Plunger, Mfi of an inch in diameter. 



SUMMARY 



Various types of fruit pressure testers used to determine the firmness 

 of fruit are briefly described. Methods of making the determinations 

 are also described, and the desirability of standardizing the methods 

 is discussed. 



As fruits mature and ripen there is a decrease in firmness; the 

 principal objective of the pressure tester is to measure the maturity 

 and ripeness of the fruits. However, other factors, such as tempera- 

 ture of the fruit, turgidity and moisture content of the fruit, soil 

 fertilization, soil moisture, thinning, and rootstocks, may also in- 

 fluence the readings and mask the relation of pressure-test determina- 

 tions to maturity and ripeness. 



Pressure-test determinations have not been found to form a reliable 

 index to maturity of apples except to indicate when certain varieties 

 are becoming too soft and overmature for storage. They do con- 

 stitute, however, a fairly accurate guide to the ripeness of apples. 

 Data are presented showing the pressure-test range, representing 

 different degrees of ripeness of a number of commercially important 

 apple varieties. 



On the other hand, with pears the pressure test has been found of 

 primary importance for establishing picking maturity standards; 

 such standards are presented- for a number of varieties. It has not 

 proved as satisfactory as a measure of ripeness during cold storage. 



With peaches and plums the pressure test may be used to establish 

 the color standards for picking. 



LITERATURE CITED 



(1) Addoms, R. M., Nightingale, G. T., and Blake, M. A. 



1930. DEVELOPMENT AND RIPENING OF PEACHES AS CORRELATED WITH 

 PHYSICAL CHARACTERISTICS, CHEMICAL COMPOSITION, AND HISTO- 

 LOGICAL STRUCTURE OF THE FRUIT FLESH. II. HISTOLOGY AND 



microchemistry. N. J. Agr. Expt. Sta. Bui. 507, 19 pp., illus. 



