Tissue sterility in uneviscerated carcasses.

Sheep muscle tissue removed aseptically from control carcasses, from uneviscerated carcasses held at 20 degrees C for 24 h, and from carcasses of sheep subjected to stress before slaughter was examined for the presence of bacteria. All samples from a total of 68 carcasses were sterile. Whole-body autoradiography of mouse carcasses showed that 14C-labeled fixed bacteria injected after death remained in the lumen of the intestine. Live bacteria did not penetrate the mucosal surface until the tissue structure had been disrupted by proteolytic enzymes. Bacteria were unable to penetrate sections of intestine longitudinally until considerable structural breakdown had occurred, indicating that blood and lymph vessels do not normally offer a pathway for microbial invasion from the intestine. Clostridia, which have been reported to be responsible for deep spoilage of meat, reached maximum numbers 24 to 28 h after death in the intestines of guinea pig carcasses stored at 20 degrees C, but did not invade carcass tissues until the stomach ruptured as a result of proteolysis between 2 and 3 days after death.

Effect of delayed evisceration on the microbial quality of meat.

The postomortem invasion of muscle and other tissues by bacteria from the intestinal tract was studied with the use of radioactive tracers. The injection of 14C-labeled bacteria or spores into the intestines of guinea pig carcasses within 24 h of death resulted in the rapid spread of 14C throughout carcasses. When live bacteria were injected along with the labeled cells, it was not possible to isolate viable organisms from the body tissues if the living animal had been exposed to the bacteria. It appears that animals are immune to their normal intestinal flora and that this immunity persists after death; thus passage of these bacteria into the lymphatic system does not necessarily result in the presence of live bacteria in carcass tissues. It therefore seems that a delay of up to 24 h before evisceration would not lead to deep tissue contamination of the carcass by organisms usually present in the intestines. Further evidence for this hypothesis was obtained by showing that muscle and lymph nodes from uneviscerated lamb carcasses hung for 24 h at 20 C remained sterile.

Methanogenic fermentation of benzoate.

A methanogenic enrichment culture decomposed small concentrations of (14)C-benzoate to (14)C(4) and (14)CO(2) under stringently anaerobic conditions with or without preceding exposure to benzoate.