Quality of Bartlett Pears Subjected to Phytosanitary Irradiation Treatment Followed by Commercial Distribution and Simulated Retail Display

California exports about 36,000 tons of Bartlett pears (Pyrus communis L.) each year. Methyl bromide is used as a phytosanitary treatment on pears, but with its imminent phase out, alternative treatments are being sought.  Irradiation is used as a phytosanitary treatment for various tropical fruit but little is known about its effect on the quality of 'Bartlett' pears. The objective of this study was to determine the effect of X-ray irradiation on the physicochemical properties and sensory attributes of early and late harvest Bartlett pears. Following harvest, the size 135 pears were stored at 30 to 32˚F for approximately two weeks.  The pears contained in 36 lb tight fill cartons were treated at a target dose of 0.4 kGy and stored at 39 to 41˚F for another two weeks. The pears were removed and stacked in layers to simulate retail market display and allowed to ripen at ambient temperature.  During ripening, the pears were tested daily for respiration rate, ethylene production, firmness, titratable acidity, total soluble solids, color, visual damage, and weight loss.  When the pears were at peak ripeness, acceptability testing was conducted with 100 consumers to determine their liking of appearance, flavor, texture, and overall liking of control and irradiated pears. There were significant differences in the responses of the early and late harvest pears to irradiation treatment. The early harvest pears showed little difference from the control for firmness, weight loss, and TSS. Ethylene production was lower for early and late harvest pears, and respiration rate was significantly higher (P≤0.05) in late harvest irradiated pears. Appearance of the pears was rated lower by consumers but there were little differences in rest of the attributes: texture, flavor, sweetness perception, and overall liking.  However, consumers rated the late harvest irradiated pears 0.5–0.6 points lower than the irradiated pears for overall liking, appearance, texture, and flavor on a 9-point hedonic scale.  Consumers perceived the irradiated pears to be less sweet than the control, which correlated with total soluble solids of 12.1% for irradiated pears vs. 13.7% for the control (P≤0.05). The weight loss of irradiated pears was significantly greater (P≤0.05) than the control, but the difference was 0.05%. Our results show that there were significant differences between the early and late harvest pears in their responses to irradiation. Given that the late harvest pears were sensitive to irradiation, a lower irradiation dose level might be warranted for maintaining pear quality.