This study was designed to evaluate effects of meat composition and freezing by conventional or cryogenic methods on microbial numbers and types in beef patties. Beef patties of different fat content or containing soy protein were frozen by liquid nitrogen, liquid carbon dioxide, or by mechanical freezing and stored at -18°C for 5 months. Cryogenic freezing produced significantly greater reduo tion in total viable mesophiies and paychrotrophs than did mechanical freezing. Patties containing 30% fat provided greater survival than observed with 20% fat or added soy protein. After frozen storage, predominant flora consisted of species of MoraxellaAcinetobacter (42%) and Pseudomonas (32%). The former group was favored by mechanical freezing, but a greater proportion of Pseudomonas app. survived cryogenic freezing than mechanical freezing.

Beef patties composed of fresh beef, blast frozen beef or combinations of fresh and frozen beef were then frozen by liquid nitrogen (LN2) or liquid carbon dioxide (LCO2) and stored at −20 C for 6 months. Analyses for various bacteria were made at monthly intervals to evaluate effects of originally combining fresh and frozen beef on the subsequent microbial flora. Of the different combinations of fresh and frozen meat, the mixture in a 50:50 ratio produced highest bacterial numbers during frozen storage. Lowest bacterial counts resulted from use of fresh beef with no blast frozen meat but frozen subsequently with LN2 or LCO2.

A study was made of the effect of spin chilling and later freezing on possible spread of salmonellae and other bacteria on commercially processed turkeys in a federally inspected plant. Sixty-one turkeys were examined before and after spin chilling, after being "shell-frozen" in brine, after blast freezing and after being held in a freezer storage room. After spin chilling, levels of all organisms tested were reduced, and no salmonellae were recovered. Coagulase positive staphylococci persisted on turkeys during processing and after freezing. As expected, freezing caused further decreases in bacterial populations, but the spin chilling operation itself was highly effective in reducing counts. No undue health hazard was observed from chilling procedures.

Dry packed broilers were cut up or kept as whole carcasses and vacuum packaged in a high barrier or low barrier fii or stretch wrapped in a tray package. In an additional study, chicken was treated with 20 ppm chlorine in a chilled water dip; control chicken had no chlorine added to the water. The poultry was then packaged as previously indicated. The chicken was stored in a display case at about 5°C and examined for various bacteria and odor development at intervals up to 10 days. Vacuum packaging dry packed broilers resulted in signMcantly lower bacterial counts and longer keeping time compared with stretch wrapped chicken. Longest shelf life was obtained with a high barrier film; and chlorine as a dip did not provide increased storage life compared with vacuum packaged broilers maintained in the dry state.

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