Hi, everyone - I got no response on Chowhound, so I thought I'd give it a shot here.
I'm not usually a big dessert person, but when I saw the recipe for crème fraîche "sorbet" posted at Serious Eats (http://www.seriouseats.com/recipes/2009/06/the-secret-ingredient-creme-fraiche-peas-mac-and-cheese-sorbet-recipe.html) I couldn't resist. Instead of adding corn syrup (which I don't own), I decided that I wanted to give the dish a little pomegranate flavor.
I reduced a thick grenadine syrup: roughly equal parts sugar and pomegranate juice (bottled, but not from concentrate), reduced to about half of its original volume, with a small splash of Cointreau added at the end for zip. While I let the syrup cool until it was tepid and viscous, I whisked one cup of the homemade crème fraîche to just barely beyond the soft-peak stage.
When I gently stirred about 1/8 to 1/4 cup of the grenadine syrup into the mix, the whole bowl immediately curdled into a watery-looking mess. For what it's worth, my theories about the disaster's cause include acid from the juice and residual heat from the syrup.
The stuff was unsalvageable, but I'd like to try the recipe again with my next batch of crème fraîche. I really like the idea of the pomegranate flavor, and I'd hate to give it up unless I had to. Does anyone have any ideas about how to prevent the same thing from happening again, or should I just try to make the dessert plain?