Shelf-life charts of beef according to level of bacterial contamination and storage temperature

Shelf-life charts of beef according to bacterial contamination and storage temperature were developed via mathematical regressions of the growth curves of spoilage bacteria in beef. Additionally, bacterial contamination in retail beef specimens was investigated using culture-based bacteriological tests, PCR assays, and pyrosequencing analysis. Pathogenic bacteria were infrequently detected in the 100 retail beef specimens, but spoilage bacteria were found in all of the specimens. The populations of spoilage bacteria in retail beef specimens varied from 2.27 to 6.15 log CFU·g−1. Pyrosequencing analysis of retail beef specimens suggested contamination from multiple sources, since both Lactobacillales and Pseudomonadales, which are prevalent in bovine intestine and feces and in bovine hides and beef-processing facilities, respectively, were detected. Growth of spoilage bacteria in beef at 5–25 °C was predicted via mathematical characterization of experimentally determined growth curves at 5, 10, 15, 20, and 25 °C using a modified-Gompertz function and subsequent nonlinear regressions of the growth characteristics, and then transformed to shelf-life charts according to the level of bacterial contamination and storage temperature. The bacterial contamination and bacteriological standards used to generate the shelf-life charts were 0, 1, 2, 3, 4, and 5 log CFU·g−1 and 5, 6, 7, and 8 log CFU·g−1, respectively.