Characterising ripening behaviour of coated pears in relation to fruit internal atmosphere.
Amarante, C., Banks, N. H. and Ganesh, S.
Postharvest Biology and Technology. Volume 23, Issue 1, September 2001, Pages 51-59.
2001
บทคัดย่อ
Pear (Pyrus communis) cultivars 'Bartlett', 'Beurre Bosc', 'Doyenne du Comice', and 'Packham's Triumph' were treated at harvest or after cold storage with concentrations of 0, 5, 10, 20, 40, and 100% (v/v) of a commercial carnauba-based wax emulsion. Fruits were assessed for ripening and internal atmosphere composition at 0 deg C/90-95% RH (only for 'Comice') and at 20 deg C/60-70% RH (for all cultivars, after they achieved the chilling requirement to ripen). For all cultivars coated at harvest and ripening at 20 deg C, respiration rates, softening and colour change followed a Michaelis-Menten model when plotted against internal partial pressure of O2 (piO2), while internal partial pressure of CO2 (piCO2) had virtually no explanatory power for these variables. This supports the notion that modification of piO2 rather than piCO2 is the principal means by which coating achieves its effects on ripening behaviour of pears during shelf life. Michaelis-Menten constant value for respiration and softening were lower than those for colour change for all cultivars at 20 deg C. This resulted in colour change being retarded by any level of depression in piO2 created by coating, while firmness was substantially reduced only at much lower piO2 during shelf life. Plots of piCO2 and respiration versus piO2 for fruits coated either pre-climacteric (at harvest) or entering the climacteric (after cold storage), indicated that 'Comice' and 'Packham's' were tolerant to hypoxia whereas, with 'Bartlett' and 'Bosc', tolerance reduced with advancing ripening, and the latter cultivar was the least tolerant of all four cultivars. During storage at 0 deg C of 'Comice', coatings had a more substantial effect in delaying softening than colour change; firmness retention seemed to be related to increase of piCO2, while the limited suppression of colour change seemed to be related to small reductions of piO2. Therefore, optimization of surface coatings for pears must account for differences between cultivars and ripening stage at which fruits are coated, as well as the temperature at which the fruits are going to be held.