INVESTIGATION AND DETERMINATION OF SAFE GUIDELINES FOR SOUS VIDE COOKING

This project seeks to do the following:Determine whether USDA appendix A can be utilized for sous vide cooking. The lowest temperature in Appendix A is 130°F (54.4 °C) with a hold time of 121 minutes. This temperature is typically described as somewhere between Rare and medium, depending on the author. If a beef steak, in vacuum packaging, is submerged in circulating 55 ° water for 121 minutes, plus an experimentally determined come up time (the time for the center to reach 54.4 °C) will it show a 7-log reduction in Salmonella? If so, then it can reasonably be assumed that the table can be relied upon. If not, then additional work will need to be done.Determine whether lower temperature treatments can be extrapolated from Appendix A. Careful examination of the table shows that the USDA is using a z-value of 10°F. That is, for each increase in temperature of 10 °F, the required cooking time is decreased by a factor of 10. Likewise, decreasing the temperature by the same amount results in a ten-fold increase in required hold time. This simple logarithmic relationship for thermal death times should mean that one can determine the required cook time for lower temperatures. So for a 125 °F temperature, it should require a 173.1 minute cook (plus come up time). This would result in a steak described as rare, and should the process be sufficient to inactivate the Salmonella at the 7-log level, that would suggest the table values can be extrapolated across the range of common doneness levels.If temperature/ time combinations cannot be either directly gleaned from Appendix A, extrapolated from Appendix A, or both, then what time/temperature combinations will effect the required inactivation? Can this data be developed into a predictive model, and if so, what are the terms/ relationships? As an example, if the 54.4 °C/ 121 minute sous vide cook is insufficient, how long of a cook (if any) would effect the required inactivation.If one or more sufficient time/ temperature combinations are suitable for producing safe products (as determined by the levels of inactivation in previous experiments), then how do these combinations affect consumer opinions of desirable flavor, texture, and acceptability? Do treatments in excess of the minimum increase or decrease consumer scores? Sous vide has often been described as a means to improve texture vs traditional cooking methods due to increased holding at low temperatures, but does this hold true when the processes are of sufficient rigor to eliminate pathogens?