MICROBIOLOGY OF SOME FROZEN AND DRIED FEEDSTUFFS

Abstract

Frozen meat by-products, liver, and fish used as components in the diets of mink and a dry cereal-type feedstuff were examined for their microbiological condition initially and after 12 and 24 hr of storage at 30 C. The dry product was moistened before incubation.Initially, frozen meat by-products and frozen liver had a similar microbiological profile. Both contained an average per gram of approximately 5.5 million total bacteria, 175 thousand enterococci, 10 to 30 thousand coliforms, and 400 yeasts and molds. Salmonellae and coagulase-positive staphylococci were recovered from 40% of the samples of both products. Salmonellae associated with these products included: Salmonella saint paul, Salmonella typhimurium, Salmonella infantis, Salmonella derby and Salmonella anatum. The frozen fish product contained, on the average, less than 10% of the number of microorganisms found in the other two products and test samples were free from coagulase-positive staphylococci. Salmonellae found in this product included: S. saint paul, S. derby, and S. infantis. Examination of the dried cereal-type mink feed revealed low numbers of microorganisms and an absence of salmonellae and coagulase-positive staphylococci.Incubation of all feedstuffs tested was accompanied by rapid growth of bacteria during the first 12 hr period and continued but slower growth during the second 12 hr period. Multiplication of yeasts and molds was minimal in the frozen feeds but was rapid in the moistened cereal product during the second 12 hr period of incubation. Coagulase-positive staphylococci grew well in the frozen feeds but multiplication of suspected salmonellae was minimal in these products.