INSTRUMENT AND OPERATOR EFFECTS ON APPLE FIRMNESS READINGS

Three apple (Malus domestica Borkh.) cultivars of various maturity lev els and flesh firmness were used to compare firmness readings obtained by three trained operators using Magness-Taylor (MT), Effegi (EF), an d Electronic Pressure Tester (EPT) penetrometers. For all cultivars an d 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 highes t readings. Operator differences were observed for all instruments exc ept when the electronic tester mas used in the default mode. Compariso ns between instruments and modes resulted in significantly different f irmness readings across operators, except for the comparison of EP vs, EPT in default mode. For most comparisons, firmness variance due to i nstrument 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 ope rators are used.