Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2003
Publication Date: 4/1/2003
Citation: Juneja, V.K., Marks, H.M. 2003. Characterizing non-linear concave survival curves for salmonella spp. subjected to different heating rates in sous-vide cooked beef. Innovative Food Science and Emerging Technologies. 4:395-402. Interpretive Summary: Salmonella is a pathogen of major concern for the food industry because of its association with several outbreaks of foodborne illness. One of the most common and effective means of controlling this bacterium is the application of adequate heat treatment. When bacterial populations are heated they usually die at a constant rate, but there are exceptions especially when very mild heating processes are used. Consequently, the food industry and regulatory agencies need a tool to choose the best mild heat treatment to apply for the production of safe food. We have developed a mathematical model that can be used to predict the destruction of the deadly pathogen during slow heating rates employed in the production of "cook-in-bag" beef. This information will be of immediate use to consumers and to the food industry and regulatory agencies to aid in the development of guidelines to ensure safety of the food supply.
Technical Abstract: Inactivation rates of a cocktail of Salmonella spp. in sous-vide cooked beef exposed to varied heating rates of 1 to 3 h from 10 C to the process- ing temperature of 58 C were determined. The primary thermotolerance response of the organism, as a result of increasing cooking times to the target temperature, was a switch to non-linear inactivation kinetics, resulting in the presence of shoulders (lag time) in the survival curves. From the survival curves obtained in this study, values for two parameters: the asymptotic D-value and the "lag" time, were estimated. The computa- tions for the non-linear curves suggested that the treatment affects the initial cell resistance (lag time), but that once this initial period is past, the heat resistance, as measured by the asymptotic D-value, is not affected by rate of cooking. At 58 C, the asymptotic D-value was estimated to be between 5.2-7.4 minutes. These findings should have substantial practical importance to food processors in sous-vide cooked beef that are processed by slow heating rate/long come-up times and low heating temperatures.