Effect of irradiation as a mitigation treatment on storage quality of early peaches and nectarines for airfreight consignments

Evaluate fruit quality to determine whether the recommended American, Animal and Plant Health Inspection Service (APHIS), maximum absorbed irradiation dose of 1000 Gy has an adverse influence on the storage quality of airfreight peaches and nectarines. Since certain early season peach and nectarine cultivars are airfreighted to overseas markets, cold treatment mitigation is not a viable option. An alternative is to use irradiation, which is a mitigation treatment approved by APHIS for use on different fruit kinds, including plums. This technology needs to be tested on peaches and nectarines with short storage protocols as required for airfreight

Peaches and nectarines were sourced from pack-houses in Limpopo, Franschhoek/Paarl and Ceres, transported to ExperiCo in Stellenbosch, and cooled to -0.5 °C. Fruit was then taken to the HEPRO Cape (Pty) Ltd irradiation facility for treatment at different dosages. After irradiation, the peaches and nectarines were subjected to simulated loading and airfreight for 24 hours at 16 °C, followed by 24 hours at 10 °C. Thereafter, fruit was stored at -0.5 °C for 3 days to simulate the distribution period overseas, after which a start of shelf-life fruit quality evaluation was done, followed by an end of shelf-life evaluation after 5 days at 10 °C.

The data from the past three seasons indicated that irradiation had no serious negative effects on the quality of the nectarines and peaches tested in this project. The fruit were still in good condition after the simulated airfreight. With most of these cultivars, there were decreases in flesh firmness with increased irradiation dosage, that will need to be managed, but no visible irradiation damage occurred. The desired minimum flesh firmness recommended for irradiation treatment is 8kg with 11 mm plumger (4.5 kg with 8 mm plunger), while the maximum flesh firmness remains that specified for export protocols.

Data confirmed that irradiation of airfreighted nectarines and peaches can be done successfully. Apart from fruit softening, irradiation generally had no significant negative effects on the quality of the airfreight peach and nectarine cultivars tested in this three-year study. It is advised to conduct future research using insect-proof packaging that is compliant with APHIS regulations, but this may be market dependant. Irradiation will be a good tool if mitigation treatments become mandatory for certain markets, especially with possible growth in the nectarine market.

Irradiation might be the only viable option for export of fruit to phytosanitary markets. This treatment might also give access to new markets. In cases where cold sterilization cannot be applied.