THE USE OF A PRESSURE TESTER TO MEASURE 

 FIRMNESS OF APPLES 



William J. Bramlage 

 Department of Plant and Soil Sciences 



Firmness of apples is used worldv\fide as a measure of ripeness 

 and "condition" of the fruit. The most widely used instrument for 

 firmness measurement is the Magness-Taylor pressure-tester (devised 

 in 1925), although the Effegi tester (developed recently in Italy) 

 has met some acceptance due to its compact size and convenience. 

 Tests comparing the Magness-Taylor with the Effegi indicate that 

 readings of the 2 instruments are quite comparable, and I shall as- 

 sume that what is said in this article about use of a Magness-Taylor 

 is equally true about use of an Effegi tester. 



With its worldwide and longstanding use, and the importance 

 of its measurements, one may assume that the Magness-Taylor is used 

 in a standard way and that readings by different users are closely 

 comparable. Not so! There is no standard technique and readings 

 are often grossly variable among users of the instrument. In 1 

 test in Geneva, New York, it was found that professional users of 

 a Magness-Taylor varied as much as 3 to 4 lbs in the readings they 

 obtained on the same lots of apples! Following an informal discus- 

 sion at a meeting in December, 1975, where it was evident that use 

 of pressure testers differed widely, 10 Northeastern post-harvest 

 horticulturists-^ agreed to 'gather data on factors that can influ- 

 ence pressure test determinations, in hopes of standardizing a tech- 

 nique. The results of this collaborative effort, coordinated by 

 Dr. G.D. Blanpied of Cornell University, are summarized here. 



The Magness-Taylor pressure tester : The instrument itself may 

 be a cause of erroneous readings. First , there are 2 sizes of plun- 

 ger "heads" that might be used. For apples, the larger one, with a 

 diameter of 7/16 inch, is always used; the smaller, 5/16 inch head 

 is for use on pears, which are much harder than apples until nearly 

 ripe. A second problem is that the instrument may not be calibrated. 

 Calibration is relatively simple and should be checked regularly. 

 To calibrate, place the plunger on an accurate scale and press down 

 slowly until the scale registers a weight that occurs on the pres- 

 sure tester scale. Check this weight against the recorded reading 

 on the pressure tester. Several different points on the scale should 

 be tested in this manner. If the readings on the scale and on the 

 tester do not correspond, the readings on apples you obtain with 

 the tester should be adjusted accordingly, or better, the spring in 

 the pressure tester should be replaced or the instrument sent to the 

 factory for re-calibration, if necessary. A rusty spring should 

 always be replaced. 



Collaborators were: G.D. Blanpied, Cornell Univ.; D.H. Dewey, Mich. State Univ.; 

 R.E. Hardenburg and A.Watada, USDA, Beltsville, Md. ; M. Ingle, W.Va. Univ.; 

 R. LaBelle d, L. Massey, Geneva, N.Y. ; G. Mattus, V.P.I and S.U., Blacksburg,Va. ; 

 W. Stiles, Univ. of Me. and W.J. Bramlage. 



