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 both before and after low temperature storage. The effect of fruit temperature on apple firmness at different times during postharvest handling is not known. Experiments were conducted to quantify physical change in apple texture 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 storage, flesh firmness and cortical tensile strength were measured on fruit at storage 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 when 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 measured at 0-3 degreesC than at 20 degreesC. 'Pacific Rose (TM)' had similar firmness and tensile strength readings when measured at 0 degreesC and 20 degreesC. 'Royal Gala' and 'Cox's Orange Pippin' were measured for firmness at different fruit temperatures at harvest and after storage. The relationship between firmness readings and fruit temperature between 0 degreesC and 20 degreesC was linear and positive at harvest and linear and negative for stored fruit. Firmness change with temperature was not affected by orchard or harvest maturity. These results suggest that physical changes in firmness with fruit temperature are common for the cultivars studied, and thus could be used to compare firmness values for fruit from different orchards that were measured at different temperatures. (C) 2001 Elsevier Science B.V. All rights reserved.