Effects of very high carbon dioxide treatment and cold storage on the quality of Navel oranges

A short, high carbon dioxide (CO2) pre-treatment in combination with cold storage has been shown to be an effective disinfestation treatment to kill quarantine pests such as fruit flies in horticultural produce. However, the effects of high CO2 and cold treatments on fruit quality, including the development of chilling injury and off-flavours, needs to be thoroughly examined. In this study, Navel oranges were treated with either air or 95% CO2 in air for 48 h at 2 degrees C then stored in air for up to 18 days at 2 degrees C. Following treatment and storage, there was no evidence of any chilling injury and no significant changes in fruit soluble solids content (SSC) or titratable acidity (TA). Another storage trial examined the time taken for Navel oranges to recover from the 95% CO2 treatment. In this experiment, fruit were stored at 2 degrees C and ventilated with either air or 95% CO2 in air for 70 h. After treatment, the fruit were stored in air and sampled after 1, 2, 3, 4, 5, 8, 9 and 10 days. The results showed that after the high CO2 treatment, the levels of acetaldehyde significantly increased in CO2-treated fruit and ethanol whereas levels of ethanol decreased. However, within three days storage in air, levels of acetaldehyde returned to pre-treatment concentrations. These results show the potential of using high CO2 combination treatments as postharvest disinfestation treatments, which do not adversely affect fruit quality after treatment and storage. However more research is recommended to fully understand these fruit responses and their role in overall fruit quality.