Gamma and X-ray Irradiation Improve Postharvest Shelf-life in ‘Bartlett’ Pears

Abstract

The objective of this study was to investigate the effects of gamma and x-ray treatment on ‘Bartlett’ pear physiology during postharvest storage. Freshly harvested ‘Bartlett’ pears were irradiated with gamma irradiation at 0.412 and 0.819 kGy and x-ray irradiation at 1.03 and 1.94 kGy, then stored at 0-1 ⁰C and 95% relative humidity. The pears were removed from cold storage at 45 and 75 days and allowed to ripen at room temperature for four and two days, respectively. Respiration rate and ethylene production were measured during fruit ripening. Color, firmness, titratable acidity, soluble solids contents, and occurrence of superficial scald was measured at the climacteric peak. Ripening was accelerated in all pears during storage, and by day 75, the fruit ripened in three days compared to seven days before storage. Ethylene production was decreased, and respiration rate was increased in the irradiated fruit in a dose-dependent manner. Superficial scald developed in pears only after 75 days of cold storage. Superficial scald was lower in pears treated at the higher doses by x-ray as compared to the lower doses and the control pears, although concentrations of alpha-farnesene and conjugated trienes, considered precursors to superficial scald, were not affected. This research suggests that the formation of superficial scald can be influenced by factors other than alpha-farnesene and conjugated trienes. Irradiation also suppressed fungal decay in x-ray irradiated pears. Despite being treated at a higher dose, the x-ray treated fruit maintained a firmer texture and delayed yellowing compared to gamma treated fruit. This research shows that the higher doses of irradiation were more effective at lowering ethylene production and decreasing superficial scald development with little impact on the quality of ‘Bartlett’ pears. Keywords: alpha-farnesene, ethylene, gamma, postharvest, superficial scald, x-ray