Instrument and Operator Effects on Apple Firmness Readings

Abstract

Three apple (Malus domestica Borkh.) cultivars of various maturity levels and flesh firmness were used to compare firmness readings obtained by three trained operators using Magness-Taylor (MT), Effegi (EF), and Electronic Pressure Tester (EPT) penetrometers. For all cultivars and operators, use of the MT resulted in the lowest mean readings, while use of the EPT operated in the MT testing mode resulted in the highest readings. Operator differences were observed for all instruments except when the electronic tester was used in the default mode. Comparisons between instruments and modes resulted in significantly different firmness readings across operators, except for the comparison of EF vs. EPT in default mode. For most comparisons, firmness variance due to instrument or mode was larger than the variance due to operator. Apple maturity did not significantly alter firmness trends due to instrument or operator. Thus, caution should be used to interpret apple firmness changes of a single lot of apples when several instruments and/or operators are used.