Comparison of a new apple firmness penetrometer with three standard instruments

The performance of a newly developed firmness penetrometer (fruit quality t ester - FQT), was evaluated over two growing seasons with poststorage apple s against the Effegi, Magness-Taylor (MT) and electronic pressure tester wi th the speed control engaged (EPT-SC). The FQT was operated in the: (a) sta ndard (FQT-Std); (b) MT (FQT-MT); and (c) EPT (FQT-EPT) modes with the latt er two simulating the operation of the MT and EPT-SC devices, respectively. 'Cortland', 'McIntosh' and 'Northern Spy' fruit were stored for 3-14 month s in controlled atmosphere (CA) conditions and were then held at room tempe rature for 1-7 days, following which firmness was measured by four operator s with each of the six instruments or modes. The ten cultivar/storage/posts torage 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 in strument performance was not consistent. However, when instrument means wer e compared for each operator, few differences were observed. The FQT-EPT an d FQT-MT simulated the operation of the EPT-SC and MT, respectively, as com parable instrument averages differed by < 1.0 N in both the hard and soft f ruit groups. Ranking of instrument standard deviations and numeric ranges i ndicated that the MT generated the most variable and widely ranging firmnes s 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 s tandard deviations and ranges generated by the three FQT modes and the EPT- SC ranked middle to lowest in both firmness categories. Based upon the comp arative evaluation criteria of similar means and relatively small standard deviations and ranges, the FQT performed as well or better than the other i nstruments tested. Crown Copyright (C) 2000 Published by]Elsevier Science B .V.