Objective: Sous vide is a relatively new cooking method introduced in restaurants in British Columbia. Sous vide cooking involves placing vacuum sealed food inside a temperature controlled water bath or steam convection oven. Unlike conventional cooking, sous vide cooking involves cooking food at a lower temperature (usually < 65°C) with a longer cook time. The low temperature allows chefs to precisely control the changes within the food. Thus sous vide cooked dishes have consistent texture and color, with retained flavor, moistness and nutrients. With all the benefits, sous vide cooking does have some disadvantages. Lower cooking temperature may not be sufficient for bacterial count reduction, resulting in unsafe food. In addition, every validated sous vide menu requires chefs to precisely follow the cooking temperature and cook time. Any deviation can cause the food to not reach the required 6.5 log reduction in bacterial count. The purpose of this experiment was to determine the effect on the internal temperature of cooking-in-process pork loin packages when additional chilled pork loin packages with an internal temperature of 4°C are submerged into the water bath.
Methods: Two groups of pork loin packages with data loggers inside (SmartButton) at approximately 4°C were introduced into a 60°C water bath at different intervals. The first group (6 packages) was immersed inside the water bath at time = 0 minute, while the second group (6 packages) was immersed inside the water bath at time = 10 minutes. Both groups were taken out when they were cooked for 31 minutes (at time = 31 minutes and 41 minutes respectively). Water bath temperature was recorded using SPER Scientific 8000024 data logger. Temperature data for pork loin packages was used to calculate the mean lethality achieved by each group. One sample t-test and two sample t-test were used for statistical analysis.
Results: There was a more than 3 mean log lethality difference in group A and group B pork loins. Pork loins cooked sous vide style in group A achieved a mean lethality of 5.12 at 31 minutes (range 0.42 to 12.78) while group B pork loins achieved a mean lethality of 8.44 at 31 minutes (range 3.35 to 11.87). With the same cook time, group A had a statistically significantly lower mean lethality than group B pork loins with p value = 0.003. Although statistically inconclusive whether group A pork loins achieved a mean lethality of 6.5, group B pork loins did reach the recommended mean lethality of 6.5.
Conclusion: The result indicated when new cold pork loin packages at 4°C are introduced into a cooking-in-process sous vide water bath at 60°C, the lethality of the original pork loin packages in the bath will be lowered if the cook time remains unchanged. However, it is inconclusive on whether the original pork loin packages will reach 6.5 lethality recommended by BCCDC. The new pork loin packages will reach 6.5 lethality if the original cook time is used., Peer reviewed, Published., Project submitted in partial fulfillment of the requirement for the degree of Bachelor of Technology in Environmental Health, British Columbia Institute of Technology, 2018.
Background: In the culinary industry, sous vide is a popular cooking method in which lower temperatures are used to cook food to retain more desirable organoleptic characteristics. However, this technique may compromise food safety as the temperature may not be sufficient enough to eliminate pathogens that may be present. The BCCDC’s Guidelines for Restaurant Sous Vide Cooking Safety in British Columbia advises when too many food items are placed in the sous vide water bath, inadequate water circulation may occur with the result that process lethality, measured by calculation of log10 reductions, may not be achieved. The purpose of this study was to determine how overcrowding a sous vide water bath would impact the thermal process of pork loins.
Methods: Each pork loin sample had a SmartButton inserted and was vacuum sealed in a plastic bag. The water bath was preheated to 60˚C by an immersion circulator. Under normal conditions, six pork loin samples were held in the water bath for 1 hour and the process was repeated four more times. Under overcrowded conditions, two runs were conducted for 1.5 to 2 hours, each consisting of 15 samples stacked in three layers. SmartButton temperature values were used to calculate whether a 6.5 log10 reduction for Salmonella spp. was achieved, using the American Meat Institute’s formula.
Results: Using a 31-minute cook time, pork loins in normal conditions reached an average log reduction of 8.85 (range: 0.51 to 21.07), which was significantly higher than the 6.5 log10 reduction objective (p = 0.006). Conversely, pork loins in overcrowded conditions reached an average log reduction of 1.76 (range: 0.05 to 7.93), which was significantly lower than the 6.5 log10 reduction objective (p = 0.000). Furthermore, cooking lethality between the two conditions, pork loins in crowded and overcrowded conditions, were found to be significantly different from each other (p = 0.000). No differences were found in the mean log10 reductions between the pork loins placed in each of the three layers in an overcrowded water bath at 31 minutes (p = 0.094).
Conclusion: Overcrowding sous vide water baths does impact on the thermal process of pork loins. Food products cooked under overcrowded conditions require a longer cook time, (approximately 30 minutes longer) to achieve at least 6.5 log10 reductions. Therefore, it is advised that food handlers using sous vide techniques should avoid overcrowding sous vide water baths. Further research using more samples is recommended to determine potential cold spot patterns in overcrowded water baths due to inadequate water circulation., Peer reviewed, Peer-reviewed article, Published., Project submitted in partial fulfillment of the requirement for the degree of Bachelor of Technology in Environmental Health, British Columbia Institute of Technology, 2018., Sous vide, overcrowding, water bath, pork loin, temperature, public health