The increasing production of Australian lemons will require the development of new export markets for high quality lemons. Many export markets require a phytosanitary treatment to ensure the absence of quarantine pests, such as fruit fly.

The three different treatments for lemons that are available are: cold treatment, irradiation, and methyl bromide fumigation.

Each of these market access treatments have their advantages and disadvantages in terms of cost, commercial applicability and market acceptance, however it is critical that these postharvest treatments do not have any negative effects on final fruit quality.

This trial assessed these different market access treatments (i.e. irradiation, methyl bromide fumigation and cold treatment) on lemon fruit quality following treatment and storage. This trial is unique as there have been many studies on the effects of these individual treatments on quality (e.g. cold treatment on lemons), but there have been no side-by-side comparison of these treatments on the same batch of fruit.

Three pallets of lemons sourced from different growing regions; Far North Queensland, Bundaberg and Sunraysia, were transported to Melbourne and treated in the commercial X-ray facility at Steritech and at a commercial methyl bromide treatment facility in Melbourne markets.

The cold treatment was carried out at NSW Department of Primary Industries. All fruit were transported under refrigeration to NSW DPI, where the fruit were stored and regularly assessed for fruit quality.

Conclusions

The results of the trial showed that all three market access treatments had similar effects on final fruit quality (overall subjective fruit quality, calyx condition), with fruit quality declining during storage and the additional shelf-life period. Fruit quality following treatment and storage was satisfactory for the market at the regular marketing stages.

In general, irradiated fruit were softer than the treatments both upon removal and after the additional shelf-life period. In addition, the irradiation treatment also resulted in higher levels of skin blemish, but this was not reflected in the overall acceptability of the fruit.

There were no consistent effects of the different market access treatments on the internal quality of the lemons. There were some effects with longer storage times, but these longer storage times (up to eight weeks) are not anticipated with high value lemon exports.

A key finding from this study was the fruit quality between growers was different and more work is required to understand the interaction of growing conditions on final fruit quality. Overall, these observations were a good result for lemon growers and exporters as it allows them to make informed decisions on market access treatment options.

This work was presented at the 2022 Citrus Technical Forum. Article authors are John Golding, Madeline Kavanagh, James Freriechs (NSW Department of Primary Industries, Ourimbah), Baogang Wang (Beijing Academy of Forestry and Pomology Sciences, China) and Penta Pristijono (School of Environmental and Life Sciences, University of Newcastle. Contact: john.golding@dpi.nsw.gov.au