Comparison of a new apple firmness penetrometer with three standard instruments

The performance of a newly developed firmness penetrometer (fruit quality tester - FQT), was evaluated over two growing seasons with poststorage apples against the Effegi, Magness-Taylor (MT) and electronic pressure tester with the speed control engaged (EPT-SC). The FQT was operated in the: (a) standard (FQT-Std); (b) MT (FQT-MT); and (c) EPT (FQT-EPT) modes with the latter two simulating the operation of the MT and EPT-SC devices, respectively. 'Cortland', 'McIntosh' and 'Northern Spy' fruit were stored for 3-14 months in controlled atmosphere (CA) conditions and were then held at room temperature for 1-7 days, following which firmness was measured by four operators with each of the six instruments or modes. The ten cultivar/storage/poststorage fruit lots were designated as either hard or soft if the poststorage firmness average for the lot was greater than or equal to or < 62.3 N (14 Ibs), respectively. Highly significant instrument by operator interactions in both firmness categories indicated that the influence of operators on instrument performance was not consistent. However, when instrument means were compared for each operator, few differences were observed. The FQT-EPT and FQT-MT simulated the operation of the EPT-SC and MT, respectively, as comparable instrument averages differed by < 1.0 N in both the hard and soft fruit groups. Ranking of instrument standard deviations and numeric ranges indicated that the MT generated the most variable and widely ranging firmness values in the hard apples, while the Effegi and the MT produced the most variable and widely ranging readings in the soft fruit, respectively. The standard deviations and ranges generated by the three FQT modes and the EPT-SC ranked middle to lowest in both firmness categories. Based upon the comparative evaluation criteria of similar means and relatively small standard deviations and ranges, the FQT performed as well or better than the other instruments tested. Crown Copyright (C) 2000 Published by]Elsevier Science B.V.