Recently, I was asked this question: “I love the taste of chocolate and orange but when I add orange zest to my coating it curdles. Why?”
This presents an excellent technical lesson in working with chocolate.
The issue is moisture.
“Curdle” is not the correct term, but I think the idea is clear – chocolate will not function properly if moisture is introduced. Even the tiniest drop of water is problematic. When water and chocolate mix, it will “seize.”
Fresh fruit, including the peel of an orange, is moist and adding it to a chocolate coating spells disaster. For this reason, chocolate candy bars use dried fruit, candied fruit, or an oil based flavoring.
You can cheat a little (and get away with it) by adding a fruit zest or juice to a ganache and then enrobing the ganache in chocolate. If the candy is eaten within a few days, the moisture captured in the creamy center should not be a problem. Truffles tolerate this process the best. Don’t add the moisture to the coating. Instead, add it to the candy center.
Another common problem arises when dipping fresh strawberries in chocolate. Make sure you dry the outer skin completely before covering in chocolate. This will buy you some time before the moisture makes it way through the fruit and to the surface of the chocolate coating. When this happens, the moisture will destroy the appearance (with bloom) and texture (making it bumpy or grainy) of the surrounding chocolate.
