Maturation and ripening of Doyenne du Comice pears : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Horticultural Science at Massey University, Palmerston North, New Zealand

Abstract

Characterisation of fruit quality attributes before and at harvest, during coolstorage and during ripening was made using standard and new, non-destructive devices during both the 1996 and 1997 seasons. Fruit firmness was linearly related to time when measured either by 'Kiwifirm' or penetrometer before harvest. Destructive techniques, the penetrometer and the texture analyser, were used to measure firmness and compared with non-destructive devices, the Kiwifirm and the softness meter. It is suggested that expressing rates of softening will be much more straightforward using a device such as the Kiwifirm. This device and the softness meter provided firmness data for pears that were too soft to measure by penetrometer. The effects of harvest date (1,11 and 21 March, 1996) and three crop loads on fruit maturity after a period of 6 weeks in coolstorage were investigated. Fruit size increased considerably during the 20 days before harvest, suggesting that periodical harvests need to be made in order to pick optimum size fruit each time. Maturity at harvest influenced the quality of 'Comice' stored at 0°C in air. Fruit from different harvests behaved differently in terms of softening behaviour and colour changes after 6 weeks in coolstorage. Crop load did not affect fruit quality attributes assessed after coolstorage. The characterisation of the nature and degree of within-tree and between tree fruit variability in harvest maturity and final ripening behaviour of 'Doyenne du Comice' pear was assessed by measuring firmness and colour. These attributes were measured non-destructively on fruit from different positions on the trees, and subsequently measured at harvest and during ripening at 20°C after 7 weeks in coolstorage at 0°C in air. Fruit behaved differently in terms of softening behaviour and colour changes depending on their position on the tree. Fruit maturity was delayed when fruit came from shaded areas, fruit from inner locations were greener than fruit from the outside and top positions. Selective picking and the association of harvest and ripening data may be important in making predictions that could reduce variability in fruit quality in the market place.