Physical change in apple texture with fruit temperature: effects of cultivar and time in storage

Flesh firmness is used to assess apple (Males domestica Borkh.) quality bot h before and after low temperature storage. The effect of fruit temperature on apple firmness at different times during postharvest handling is not kn own. Experiments were conducted to quantify physical change in apple textur e readings with change in fruit temperature. 'Royal Gala', 'Granny Smith', and 'Pacific Rose (TM)' apple fruit were stored at 0 degreesC , while 'Cox' s Orange Pippin' was stored at 3 degreesC. At different times during storag e, flesh firmness and cortical tensile strength were measured on fruit at s torage temperature, after 24 h at 20 degreesC, or after 24 h at 20 degreesC followed by 24 h at the storage temperature. 'Royal Gala', 'Granny Smith' and 'Cox's Orange Pippin' fruit had higher firmness readings at harvest whe n measured at 20 degreesC than at 0-3 degreesC, but after 50-100 days at 0- 3 degreesC firmness and tensile strength readings were greater when measure d at 0-3 degreesC than at 20 degreesC. 'Pacific Rose (TM)' had similar firm ness and tensile strength readings when measured at 0 degreesC and 20 degre esC. 'Royal Gala' and 'Cox's Orange Pippin' were measured for firmness at d ifferent fruit temperatures at harvest and after storage. The relationship between firmness readings and fruit temperature between 0 degreesC and 20 d egreesC was linear and positive at harvest and linear and negative for stor ed fruit. Firmness change with temperature was not affected by orchard or h arvest maturity. These results suggest that physical changes in firmness wi th fruit temperature are common for the cultivars studied, and thus could b e used to compare firmness values for fruit from different orchards that we re measured at different temperatures. (C) 2001 Elsevier Science B.V. All r ights reserved.