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Tasmanian Institute of Agriculture

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Published: 13 Feb 2019

You wake up on a glorious summer morning and make your way to the fridge.

It’s time for a nibble of last night’s leftover dessert – a crisp, refreshing fruit salad.

And yet, something has happened in the night. This mushy, brownish concoction barely qualifies as fruit, let alone salad.

So what happened?

Odds are your dessert included a climacteric fruit, or fruit that keeps ripening after it’s picked.

Think banana, or kiwifruit.

A gas released by a certain fruit has altered the freshness of your sweet after-dinner treat.

Luckily for all of us, Yan Lee is chasing down the perfect recipe for fruit salad through his PhD with the ARC Training Centre for Innovative Horticultural Products, located at the Tasmanian Institute of Agriculture (TIA).

“I’m investigating how sensitive watermelon is to ethylene,” Yan said.

Ethylene is the gas released by many fruit and vegetables as they ripen. And Yan’s research is turning up some unexpected results.

“It was thought that watermelon wasn’t sensitive to ethylene at low concentrations, but my research is proving this wrong,” he said.

Yan is conducting his research with the fresh food company Perfection Fresh, the University of Newcastle's postharvest team and TIA’s food safety researchers.

Through his experiments, Yan has found that a small level of ethylene does actually reduce the shelf life of watermelon.

“Watermelon doesn’t keep ripening – they are non-climacteric and are harvested at full maturity – but ethylene can speed up spoilage,” he said.

“Ethylene is used commercially to control the ripening process of climacteric fruit, like bananas and kiwifruit.”

Ethylene is in the air within produce trucks, in distribution centres, and supermarkets, and probably in your own kitchen.

“Ethylene isn’t dangerous but keeping ethylene as low as possible helps keep watermelon fresher for longer,” Yan said.

This is good advice for novice fruit salad makers and food companies, alike.

Yan has given watermelon the ‘all-clear’ for fruit salad leftovers that have been stored in the fridge.

“Watermelon is good for fruit salad as long as the other fruits don’t emit much ethylene. That’s one reason why you don’t find banana in an Australian fruit salad product,” he said.

Yan’s next step is to test his findings on watermelons that have just been harvested.

“I’m growing my own watermelon at TIA’s horticulture centre. This means I’ll have watermelons that have not been exposed to any ethylene,” he said.

“I want to find out what happens to the shelf life of ‘fresh-cut’ watermelon if the exposure to ethylene has been controlled since harvest.”

More details on the project and a link to Mr Lee’s research publication are available at utas.edu.au/tia/ethylene-watermelon.

Picture: Yan Lee says that watermelon is a superb ingredient for a really fresh fruit salad.