Most mascarpone recipes you find will warn against using ultra-pasteurized cream. So the recipes say, it gives the finished product an “off” flavor. That’s not true any more than ultra-pasteurized milk has an “off” flavor relative to plain ol’ pasteurized milk. Does better, fresher low-heat-pasteurized cream make better mascarpone than the ultra-pasteurized equivalent? No question. Better ingredients always yield a better finished product. However don’t let the fact that you only have access to supermarket-brand ultra-pasteurized cream prevent you from making mascarpone (or anything else). The results will still be far superior to the pre-packaged stuff.