High-temperature, controlled-atmosphere treatments were explored for disinfestation of codling moths from `Bartlett' pear fruit. Fruit were freshly harvested in 1996 and 1997 and sorted for uniformity and absence of defects. Fruit were exposed to forced-heating at 46 °C for 1, 2 and 3 h in either air or a controlled atmosphere of 1% oxygen and 15% carbon dioxide. Fruit were evaluated during ripening at 20 °C immediately after treatment (1997 only) and after 3 weeks of cold storage at -1 °C. Fruit were ripened with and without an exogenous ethylene treatment in 1997. Heat treatments, and particularly heat plus CA treatments, slowed fruit ripening, even after fruit had been stored for 3 weeks. The longer the treatment, the greater the inhibition. Fruit from longer treatments were firmer than untreated fruit after 4 days of ripening, but treatment with exogenous ethylene did not overcome the inhibition in the rate of ripening, although fruit from all treatments softened faster. The mortality of codling moths following exposure to the same treatments was also determined. With the heat plus controlled-atmosphere treatments, 100% mortality was achieved in 2.5 h with the faster heating rate used in our 1996 experiment, while it took 3 h to achieve 100% mortality with the slower heating rate.
Elizabeth Mitcham, Lisa Neven, and Bill Biasi
Elena De Castro Hernandez*, Bill Biasi, and Elisabeth Mitcham
The internal browning (IB) disorder of `Pink Lady' apples is the manifestation of some undefined physiological conditions of the fruit at harvest, which predispose them to damage during CA storage. Internal browning problems generally occur intermittently and in unpredictable patterns. This type of disorder has the potential for widespread economic impacts. The optimum storage conditions and underlying physiological factors remain understood. In Fall 2002, `Pink Lady' apples were harvested in Stockton, Calif., at two maturities, then placed into CA storage. After storage, the percentage of fruit with IB increased with greater CO2 and with lower O2 concentrations. The incidence of IB injury was greater in fruit from the second harvest, but there was not a great difference in incidence between 2 and 6 months of storage. In Fall 2003, `Pink Lady' apples were harvested on the same orchard at three maturities and placed into CA storage. In all three experiments, fruit were stored in either air, 2% O2 + 1% CO2, or 2% O2 + 3% CO2 at 0.5 °C. In the first experiment, three harvest maturities were placed into storage immediately after harvest. For the second experiment, apples from harvest 2 were treated prior to fruit storage with 1ppm 1-MCP for 24 hours, 2200 ppm DPA, or were untreated. In the third experiment fruit from harvest 3 were placed into CA storage after 0, 2, or 4 weeks in air at 0.5 °C. No IB was observed for any of the three maturities after 0.5 and 1 month storage. After 2 months IB injury was present in 4.8% of the fruit stored in 1% CO2 and 4.6% stored in 3% CO2 from harvest one. A lower percentage of IB was observed in harvest two. Harvest three presented 0% and 2.6% of IB in 1% and 3%CO2 respectively. The effect of 1-MCP,DPA and delayed CA on IB will be discussed.
Elena de Castro, Bill Biasi, Elizabeth Mitcham, Stuart Tustin, David Tanner, and Jennifer Jobling
To investigate a flesh browning (FB) disorder in Pink Lady apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. cv. Cripps Pink], fruit were harvested from the same orchard each year from 2002 to 2005, at two or three maturity stages each year. Fruit were kept in air or controlled atmosphere (CA) storage (1.5- to 2-kPa O2 in combination with 1-, 3-, or 5-kPa CO2) at 0.5 °C. Additional subsets of fruit were exposed to 1 μL·L−1 1-methylcyclopropane (1-MCP) for 24 hours and dipped in 2200 μL·L−1 diphenylamine (DPA) for 5 min or held in air at 0.5 °C for 2 or 4 weeks before CA storage. Flesh browning was not seen in air-stored fruit but appeared in CA-stored fruit as soon as 2 months after harvest. Flesh browning incidence did not increase after longer storage times. Flesh browning increased with increasing CO2 concentration and decreasing O2 concentration in storage. 1-MCP did not significantly affect FB incidence, while delaying CA by 2 or 4 weeks reduced it. Diphenylamine eliminated FB incidence. When similar storage atmospheres were compared for the four seasons, FB incidence was high in 2002 and 2004 and low in 2003 and 2005. Concentrations of B, Ca, and Mg in apple flesh and seasonal field temperatures during the growing and harvest periods were related to FB incidence in 2002, 2003, and 2004 but not in 2005. The relationship of these pre- and postharvest factors to FB susceptibility are discussed.
Maria Monzon*, Bill Biasi, Shaojin Wang, Juming Tang, Guy Hallman, and Elizabeth Mitcham
The Mexican fruit fly infests many tropical and subtropical fruits, consequently fruits must be treated for quarantine security. Although chemical fumigations are the most common quarantine treatments, interest in using cold and heat treatments has increased due to concerns over environment and human health. Recently, shorter heat treatments such as those provided with radio frequency (RF) energy have been studied on walnuts and various fresh fruits as a possible quarantine treatment. Preliminary studies with a heating block system showed that reaching temperatures of 50 °C with a holding period of 2 min. or 48 °C for 6 minutes was required to achieve 100% insect mortality of 600 third instar Mexican fruit flies (the most heat resistant insect stage). Doubling the holding time required to achieve 100% insect mortality would likely be necessary to provide for Probit 9 security. Fresh fruits such as persimmons and guavas are commonly infested by the Mexican fruit fly. Persimmon and guava fruit were treated with RF energy to temperatures ranging from 48 to 52 °C at different holding periods. After treatments fruit were evaluated for external appearance, decay, soluble solids, titratable acidity, internal flesh quality, and ethylene production and respiration rate. Persimmon fruit tolerated the lower temperature, 48 °C for up to 18 min., but temperatures above 50 °C for more than 1 minute caused internal damage. Preliminary studies with guava indicate that fruit may tolerate 50 °C, but fruit quality after storage is still to be evaluated.
Maria E. Monzon, Bill Biasi, Elizabeth J. Mitcham, Shaojin Wang, Juming Tang, and Guy J. Hallman
The external and internal quality of ‘Fuyu’ persimmon fruit (Diospyros kaki L.) was evaluated after heating with radiofrequency (RF) energy to 48, 50, or 52 °C, holding at the target temperatures for durations ranging from 0.5 to 18 minutes, hydrocooling, and ripening at 20 °C for 12 days. These treatment conditions were identified for control of third instar Mexican fruit fly larvae (Anastrepha ludens). The treatments had no commercially significant effect on firmness, soluble solids content, titratable acidity, or weight loss of the fruit. RF-treated persimmon fruit attained a deeper orange–red skin color than control fruit. There was a greater incidence of slight to moderate flesh browning in fruit heated to 50 and 52 °C as compared with 48 °C. Calyx browning increased slightly in all RF-treated fruit and was the highest in the longer treatments at each temperature. Heating persimmon fruit with RF to 48 °C and then holding for 6 or 12 minutes showed the least damage, and the latter treatment was longer than should be required for a quarantine treatment against the third instar Mexican fruit fly. Holding persimmons for 6.6 minutes at 48 °C should provide control of the Mexican fruit fly and maintain fruit quality. Confirmation tests with infested fruit should be conducted.