Factors affecting post-storage quality of ‘Nules Clementine’ mandarin fruit with special reference to rind breakdown

Khumalo, Ngcebo Parton (2006-12)

Thesis (MSc (Horticulture))--University of Stellenbosch, 2006.

Thesis

Rind breakdown of ‘Nules Clementine’ mandarin (Citrus reticulata Blanco) is a physiological rind disorder that develops during storage. The disorder appears following leakage of essential oil from oil glands in the flavedo, which then leaks into and oxidises the albedo. Oxidised tissue appears as brown spots in the rind. Occurrence of this disorder over the years has caused high financial losses to ‘Clementine’ mandarin producers and exporting companies. Therefore, research aimed at solving this problem was identified as a priority by the citrus industry. Several factors have been reported to be associated with rind breakdown of ‘Clementine’ mandarin fruit, and include environmental factors, fruit maturity at harvest, ethylene gas degreening, storage temperature and storage duration, canopy position where fruit are borne, plant growth regulators, and differences in susceptibility among selections. Practical information has been generated on rind breakdown, but the basic physiology of the disorder is still unresolved. The objective of this study was, therefore, to quantify the effects of various factors on the development of rind breakdown of ‘Nules Clementine’ mandarin fruit, as well as to establish an association between rind pigments and rind antioxidant capacity on the development of this disorder. In this study a series of five experiments was conducted, and included quantifying the differences in susceptibility to rind breakdown between ‘Nules’ and ‘Oroval Clementine’ mandarin fruit, investigating the effects of fruit canopy position, harvest date, ethylene gas degreening, storage temperature and duration on the development of rind breakdown. The effect of these factors on rind pigments and antioxidant capacity was also reported. Generally, ‘Nules’ and ‘Oroval Clementine’ mandarin fruit exhibited similar characteristics at harvest, in terms of maturity and antioxidant capacity. After storage, ‘Nules Clementine’ mandarin developed higher levels of rind breakdown than ‘Oroval Clementine’ mandarin. However, the difference in susceptibility to rind breakdown of ‘Nules’ and ‘Oroval Clementine’ mandarin fruit could not be associated with the antioxidant capacity measured at harvest...

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