SAN FRANCISCO (Standard&Poor's) Nov. 27, 2012--Standard&Poor's Ratings Services today placed its 'BBB' long term corporate credit rating, 'A-2' short term and commercial paper, and all issue-level debt ratings on Omaha, Neb.-based ConAgra Foods Inc. on CreditWatch with negative implications, meaning that we could lower or affirm the ratings following the completion of our review. At the same time, Standard&Poor's placed Ralcorp Holdings Inc.'s (BBB-/Negative/--) issue-level ratings on CreditWatch with negative implications, meaning that we could lower or affirm the ratings following the completion of our review. Ralcorp's 'BBB-' corporate credit rating is affirmed. The outlook on the corporate credit rating is negative. ConAgra's CreditWatch negative listing follows its announcement that it will be acquiring