I made a horseradish cream veloute once and it was excellent. The last two times I've made it, there wasn't the "bite" that I was looking for from the sauce. Once thing that I might have done differently was that I simmerred the horseradish (prepared hot, and then fresh grated the second time) in the sauce for a while before serving. I'm starting to think that I should just make the veloute, then add the horseradish at the end. It seems to lose its flavor after simmering. Any similar experiences? I'm not sure what chemical gives the horseradish its flavor.