I bought some ground round this week to make into hamburgers. The exterior was red, but when I broke it up to make the patties some of the interior was brown. It came from a reputable market prepackaged and wasn't marked down or anything. This is the second time I've experienced this at this particular market. It tasted fine and didn't smell funny. I know that some times this will happen on the surface with the interior staying red, but brown inside with a red exterior is weird. Any thoughts on how this could happen?