Evaluating the risk of contracting salmonellosis from egg yolk "parmesan" based on water activity

Abstract

Background: Egg yolk parmesan recipes have been gaining popularity since 2015. Most recipes include a heat treatment step which would kill egg-associated pathogens such as salmonella, however a significant number of recipes do not; resulting in a higher risk of salmonella growth and thus higher potential to cause food borne illness. Methods: Salt-curing affects an intrinsic factor called water activity (Aw). At 0.93 Aw or below salmonella is unable to grow. This study measured the minimum amount of time required for the salt curing process to inhibit the growth of salmonella. To achieve this batches of egg yolk parmesan were made using varying curing durations and then the water activity of the finished product was measured. A one sample t-test statistical analysis was conducted to determine if, with 99% confidence, the water activity of yolks cured for the chosen duration can reliably reduce water activity below 0.93. Results: The minimum amount of time required for the water activity to decrease below 0.93 was 24 hours. Results were as follows: N = 39; the p-value is 0.0000000 and the power is 1.0000000. Conclusion: This is strong evidence to suggest that large grade A chicken egg yolks cured in a 74% kosher salt and 26% white granulated sugar mixture for 24 hours at refrigeration temperature will have a water activity below 0.93. Therefore, it can be concluded that curing for 24 hours will inhibit potential salmonella growth.