Utilizing the I_AD index to predict 'Rocha' pear quality and physiological disorders after storage

In order to use the index of absorbance difference (I_AD), as a fruit maturity evaluator and to assess postharvest physiological disorders, fruits from three 'Rocha' pear orchards (A, B, C orchards) were harvested on 8 dates during 6 weeks. At harvest, the fruits were separated into three classes of I_AD (1.4-1.6, 1.6-1.8 and 1.8-2.0 or class I, II and III, respectively). One batch of fruits was stored in normal atmosphere storage (NA) for 23 weeks and the other batch in a dynamic controlled atmosphere (DCA) for 31 weeks. Standard quality parameters of the fruits were evaluated at harvest, and after 0 and 5 days of shelf life at 20°C. At 7 days of shelf life superficial scald and internal browning fruit incidence were evaluated. At harvest, the I_AD index was related with firmness and ethylene production rate (r²=0.74 and 0.76, respectively) but the correlation was poor between I_AD and total sugar content and fruit size (r²=0.10 and 0.45, respectively). Regarding NA storage, with the exception of orchard C, the fruits of I_AD class I, for orchards A and B, 13.1% of the fruits showed superficial scald and 11.1% internal browning. The best results were from fruit of the orchard C of the I_AD class III, which had 0.8 and 9.2% of superficial scald and internal browning, respectively. Considering the fruits of DCA, fruits from orchard B and of the I_AD class III showed the lowest incidence of internal browning (6.2%). These results show that the orchard has a strong influence on physiological disorders and the I_AD index may be insufficient to be used as the only criterion to set the harvest date and predict the level of incidence of physiological disorders.