Some old archived posts from the Citrus Growers Forum:
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pagnrLocation: Australia
23 March, 2010
In my climate, Swingle fruit are far better than Poncirus, something like a dull grapefruit flavor, with a fair hint of Poncirus flavor. The juice is ok for interests sake, I would say quite acceptable, but not comparable to common Citrus.
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gregnLocation: North Vancouver, BC, Canada [note: this is not where the citrus expo was held]
07 April, 2010
I tasted the Swingle citrumelo at last years citrus expo - the seeds were used in Stan McKenzie's seed spitting competition. They weren't as horrible tasting as I was led to believe. Definitely not grocery store fruit but a worth plant to grow outside the traditional citrus growing areas.
I have been told that the Dunstan citrumelo is MUCH better.
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http://citrusgrowersstatic.chez.com/web/viewtopicaf81.phpAlso someone noted on the Cold-hardy citrus Wikipedia pages that "Semi-edible, 'Dunstan' is considered the most edible citrumelo."
I believe both Swingle and Dunstan are hybrids between Duncan grapefruit and trifoliate orange, so that would make them siblings.
One more post from somebody else:
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shane11December 3, 2013
My 'dunstan' citrumelo produced for the 1st time this year and they are surprisingly good. I squeezed a fruit and added slightly more water than juice and a little sugar. This tasted very much like grapefruit juice, in fact almost identical. Because these are more sour than grapefruit I bet they will be excellent used as a lemon or lime substitute if the juice is used straight. I plan on trying this very soon. i have also heard they make a very good "lemon" pie, one person from NC even told me they were better than the real thing. I am somewhat perplexed as to why these are so uncommon. This is a great find for anyone wanting to grow an edible Citrus in zone 7.
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"Friend's first citrumelo fruit" (in the Palms & Cycads category) Gardenweb/Houzz forum
https://www.houzz.com/discussions/friends-first-citrumelo-fruit-dsvw-vd~2103184Okay, this last post is probably overly optimistic, but it does suggest that at least some people find the flavor to be not that bad.