Do you mean un-cured rubber? I'd guess you'd want to re-mill it before curing, at a minimum.
I don't think there is much you could do about bloom in cured rubber. It's a function of what is in the rubber, and you can't do much after curing it other than let it leach out if it's going to.
Is this a sulfur cured epdm? You could think about switching to a peroxide cure...