Mangoes rested at ambient shed temperature key to hot water disinfestation

They just need a rest in the shed prior to be being dipped.

Hot water treatment is used extensively to disinfest other fruit and vegetables in order to meet international protocols for fruit fly disinfestation.

However, its application on mangoes has been hindered by scalding to the skin which compromises fruit quality and value.

But research by the WA Department of Primary Industries and Regional Development (DPIRD) found the R2E2 and NMBP-4069 varieties responded well to the hot water treatment, without scalding, when the fruit was preconditioned to ambient shed temperatures.

Two years of trials were undertaken at DPIRD's Frank Wise Agricultural Research Institute at Kununurra, as part of a Commonwealth Australian Centre for International Agricultural Research (ACIAR) project, in collaboration with Griffith University, Queensland.

The trial examined two preconditioning treatments of six and 24 hours for both mango varieties.

This was followed by hot water treatment at the protocol standards of 46 degrees for 20 minutes and 47 degrees for 15 minutes, followed by hydrocooling at 30 degrees for 30 minutes.

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DPIRD research scientist Tara Slaven said NMBP-4069 proved to be the more versatile variety, with two preconditioning treatments responding well.

"This included six hours preconditioning at 34.8 degrees, prior to hot water treatment of 46 degrees for 20 minutes, as well as 24 hour preconditioning at 34.8 degrees, before a 15 minute hot water treatment at 47 degrees," Ms Slaven said.

"R2E2 also performed well under preconditioning of 42 degrees, for six hours when treated at 46 degrees for 20 minutes."

Ms Slaven said the trial results opened the way to an alternative disinfestation option at significant lower infrastructure costs to vapour heat treatment and irradiation for mango growers and packing houses.

"The trial has shown that preconditioning these mango varieties at ambient Kimberley temperatures could be a useful, cost effective, efficient system to disinfest mangoes without scalding the skin," Ms Slaven said.

"The process still needs refinement, including examining how to keep the water temperature constant, whether the process can be adopted in other environments, like Carnarvon, and examining the potential to scale up for automation."

The trial results are now being shared with industry stakeholders internationally, as part of the ACIAR's work where scientists use their skills to benefit partner countries, while contributing to solutions that meet Australia's own agricultural challenges.

Griffith University senior horticulturalist Peter Johnson said the outcomes from hot water treatment trial could generate far reaching benefits to mango growers around the world.

"This comparatively simple treatment makes disinfestation accessible to mango growers in countries that cannot afford typical treatments, which could help improve fruit quality and profitability," Mr Johnson said.

"It will also assist mango growers to satisfy increasingly discerning phytosanitary requirements, enabling exporters to target premium markets, like New Zealand, Korea and Japan."

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