Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2019
Publication Date: 2/26/2019
Citation: Gunther, N.W., Abdul Wakeel, A.Y., Ramos, R.V., Sheen, S. 2019. The evaluation of hydrostatic high pressure and cold storage parameters for the reduction of Campylobacter jejuni in chicken livers. International Journal of Food Microbiology. 82:249-253. https://doi.org/10.1016/j.fm.2019.02.014.
Interpretive Summary: In recent years there has been multiple outbreaks of human disease caused by eating chicken livers contaminated with the bacteria Campylobacter jejuni. The bacteria are very commonly found in chicken livers in large numbers. Chicken livers are often undercooked because of a desire for the finished liver to still have a slight pink color when serving. For this reason the bacteria are often not killed by the limited cooking process allowing the bacteria to infect those eating the undercooked chicken livers. The application of high pressure to food products is a well-respected method for reducing bacteria in raw foods without the application of cooking temperatures. The work presented in this manuscript is the first time high pressure treatments have been applied to chicken livers for the purpose of killing contaminating Campylobacter jejuni. Additionally, this study looks at the application of different cold storage conditions in conjunction with high pressure treatment to determine the best cold storage for additional reductions of bacterial numbers. Finally, we looked an alternative method for applying high pressure that had in previous research produced increased reductions in bacterial numbers. High pressure treatments proved to be moderately successful at killing Campylobacter jejuni in chicken livers. The high pressure was able to reduce the numbers of bacteria contaminating both the surface and interiors of the chicken livers. This is ideal given previous research showing that the bacteria were found both internally and externally during naturally occurring contaminations of chicken livers. However, increased pressure levels needed to kill almost all of the contaminating bacteria in the livers also caused some color changes in the livers that might concern consumers. Lower pressure levels followed by cold storage increased the overall killing of the Campylobacter jejuni but did not reach the levels achieved by the higher pressures that negatively impacted the chicken livers. Previous research had suggested that multiple shorter pressure treatments compared to one longer constant pressure treatments may be more successful at killing bacteria. Unfortunately, when this approach was applied in chicken livers it did not increase the pressure treatments ability to kill Campylobacter jejuni in the livers. In conclusion, the application of moderate levels of high pressure followed by storage in the freezer for at least 48 hours provides a good reduction in the numbers of Camplylobacter jejuni contaminating chicken livers. However, to completely kill all of the Campylobacter jejuni contaminating chicken livers it will be necessary to find an additional technique to add to this process. Future research will look at adding marinades with antimicrobial components to this process.
Technical Abstract: In recent year reoccurring Campylobacter mediated outbreaks of human disease have been linked to undercooked chicken livers. A need exists for interventions to significantly reduce the Campylobacter numbers present in this widely consumed poultry product. In this study high pressure processing (HPP) techniques were applied to experimentally contaminated chicken livers to determine the Campylobacter jejuni reducing potential of this technology in the specific food matrix. HPP was able to significantly reduce C. jejuni numbers in Chicken livers with the application of 350 MPa for 5 minutes producing an average reduction of 3.4 logs. Unfortunately, livers processed in this manner displayed some changes in color. A more modest pressure of 250 MPA applied for 10 minutes did not produce an obvious color change; but only produced an average reduction in cell numbers of 1.3 logs. Cold storage conditions were able to produce 0.2 to 1.3 logs of reduction depending on the temperature and storage time and this effect combined with a HPP reduction in an additive fashion. Pulsed HPP techniques were not observed to produce C. jejuni reductions that exceeded the average reductions observed for constant pressure application at similar time intervals. HPP is a potential method for reducing C. jejuni numbers in chicken livers but given its effects on the appearance of the food product at higher pressure levels it will most likely need to be combined with additional intervention techniques.