A decades-long journey to produce delicious, commercially successful, new varieties of custard apples is inching closer to completion, ABC News reports.

According to the publication, custard apples - also known as sugar-apples and sweetsop - have a very tropical flavor with a rich creamy taste.

While they are native to the tropical Americas and West Indies, Australia is forging the category's commercial future with the world's largest breeding program.

Scientist Grant Bignell and field operations manager Dave Bruun are the brains behind one such program at the Queensland's Maroochy Research Station. As part of the 25-year-long job, they said they've taste-tested thousands of weird and wonderful fruits from orchard trials.

As for their harvests, the partnership says they come in a dizzying array of shapes, colors and sizes; some completely impractical for transport.

"It's sometimes the luck of the draw when you're in the breeding project," Bignell commented.

Red-skinned custard apple variety viewed as "The Holy Grail"

Since the trials began a quarter of a century ago, the researchers have released just one new commercial variety - Maroochy Gold.

It thrived on farms in the Glass House Mountains and Atherton Tablelands; however, it did not perform well in northern New South Wales.

Breeders expect it will take another two to three years to release three new green-skinned varieties, the publication reported.

Meanwhile, a red-skinned fruit is now being tested on a small scale on farms.

"It's been a long process for the industry," Custard Apples Australia president Daniel Jackson said.

Yet he's hopeful that a red-skinned variety would perform very well with consumers.

Bignell added: "People's eyes light up when they see the red custard apple, it definitely has potential for the Asian markets for sure."

Australia produced around 830,000 kilograms of custard apples last year, Jackson commented.

This year's crop is expected to set a record, thanks to new farmers entering the industry.

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