Live, Learn, and Read Labels

I made a startling discovery recently. The same whole milk sold under HEB's Central Market Organics label is not the same in the half-gallon as the gallon size. The half-gallon is ULTRA-pasteurized. The gallon is not. I thought maybe this was a mistake, but the expiration dates correspond perfectly. The gallon has a much shorter shelf life than the half-gallon. Needless to say, I am now buying the gallon size exclusively. I don't know why there is a difference. I suspect they are processed/packaged at totally different facilities. I have learned from researching gluten-free candy, that size can make all the difference. A chocolate bar in one size is safe, but the same brand bar in a different size is not safe because it is made in a different facility that also processes wheat products.