there is some research that says keeps fruit cold while squeezing preserves more of the enzymes as the blender or juicer produces heat which kills them. That said, a handful of ice thrown in should do the same.
Good idea! Yeah the heat produced if you're using a blender kills the enzymes but does it follow the thought if you refrigerate or freeze veggies and fruits before juicing the enzymes are preserved? How come? If heat is produced while grinding in a high speed blender I'm sure even if your fruit or veggie is frozen, it will still produce heat. But if you're using a juicer it won't kill the enzymes as it slowly rotating and grinding the veggies with minimal heat so enzymes retained.