Tree age and fruit size in relation to postharvest respiration and quality changes in 'Kinnow' mandarin fruit under ambient storage

- The respiration rate of all fruit declined during shelf-life and significantly determined by tree age but not by fruit size.
- Small sized fruit from tree age of 35-years had more respiratory substrates like sugars and organic acids and respire faster than other tree age and fruit size groups.
- Ethylene and CO2 correlated positively with TSS, titratable acidity and total sugars (%) and negatively with rind thickness.

The conducted research focused on the impact of tree age and fruit size on postharvest respiration as well as changes in physico-chemical quality of 'Kinnow' mandarin fruit, stored in ambient conditions (20 ± 2 °C). Fruit from three different tree age groups (6, 18 and 35-years) and fruit size (large, medium and small) groups were analyzed for respiration and fruit quality during seven days ambient storage. Fruit from tree age group of 35-years surpassed the fruits from tree age group of 6-years in carbon dioxide (CO2) production, while fruit size had non significant influenced CO2 production following ambient storage. Ethylene production was predominantly more in fruit from tree age group of 35-years, while fruit of small size irrespective of tree age group had significantly higher ethylene production. In general, CO2 production indicated a non-climacteric pattern, while ethylene production followed climacteric pattern, with two peaks. As regards fruit quality, fruit of tree age group of 35-years, had more TSS (10.6°Brix) titratable acidity (TA) (0.81%), sugars {reducing (1.9%), non reducing (5.3%) and total sugars (7.5%)} as compared to tree age group of 6 and 18-years. Final fruit quality data after seven days of ambient storage showed more decrease in TA (0.1%) and reducing sugars (0.26%) and increase in ascorbic acid (AA) (3.38 mg 100 mL−1) and non reducing sugars (0.61%) in fruit of trees age group of 35-years. Fruit from 18-years old trees had higher mass loss (8.39%), irrespective of fruit size and the interactive response of tree age and fruit size revealed that more mass loss (11.71%) was observed in small sized fruit from 18-year-old trees. Ethylene production was positively correlated with mass loss (r = +0.734) in fruit from 18-year-old trees and negatively (r = −0.692) in fruit from 6-year-old trees. Irrespective of tree age and fruit size ethylene and CO2 correlated positively with TSS, titratable acidity and total sugars and negatively with rind thickness.