Pear (Pyrus communis L.) cultivars 'Bartlett', 'Bosc', 'Comice', and 'Packham's' were treated at harvest or after cold storage with a carnauba-based wax emulsion at concentrations of 0, 5, 10, 20, 40, and 100% (v/v) of the commercial formulation. Fruit coated at harvest were assessed for internal partial pressure of O 2 and CO 2 , ripening, physiological disorders, and sensory attributes when held at 20°C and 60-70% relative humidity after achieving the chilling requirement to ripen, whereas fruit coated after cold storage were only assessed for physiological disorders. With the exception of 'Bosc', increasing the coating concentration improved the finish of the skin. Only 'Bosc' developed off-flavours when treated with the undiluted coating. Increasing coating concentration reduced fruit internal partial pressure of O 2 , suppressed ripening and reduced the incidence of senescent breakdown. 'Comice' pears treated at harvest with 40% coating concentration and cold stored for 6 months had delayed ripening, no senescent scald and no internal disorders after a 7-day shelf-life period.
H01 032 Received 27 June 2001; accepted 2 November 2001'Bartlett' and 'Bosc' treated at harvest with coating concentrations >10% and >40%, respectively, developed an internal disorder possibly associated with excessive internal atmosphere modification during 0°C storage. They did not develop the disorder when treated after cold storage. These findings show that response differences related to cultivar and storage temperature after coating must be taken into account in the optimisation of surface coatings for pears. Also, a given surface coating treatment may impair postharvest quality because treated pears may soften without changing colour.