Submitted to: 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., Scullen, O.J., Sommers, C.H. 2019. The evaluation of gamma irradiation and cold storage for the reduction of Campylobacter jejuni in chicken livers. 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 and 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. Irradiation of food products is a well-studied method for safely reducing bacterial numbers in raw foods in order to reduce the potential for these foods to cause disease in humans. This study is the first time though that irradiation has been applied to chicken livers with the intent of killing the Campylobacter jejuni bacteria commonly found to contaminate this food product. Additionally, this study applies common cold storage conditions in conjunction with the irradiation to determine the best ways to store chicken livers both before and after irradiation in order to kill the contaminating bacteria. Irradiation was very successful at reducing the Campylobacter jejuni present in chicken livers. Commonly utilized irradiation doses were able to completely destroy all of the bacteria present in the livers. We also discovered that storing livers frozen before irradiation reduced the effectiveness of the irradiation treatment, requiring larger doses of irradiation to achieve the same level of bacteria killed in the livers. Conversely, freezing the livers after irradiation produced even greater reductions in the bacteria numbers than was achieved by just irradiation of the livers alone. Therefore, we can recommend if irradiating chicken livers; that after harvesting the livers they are stored only in refrigerators before irradiation treatment and then after treatment are stored in the freezer for around 48 hours or longer.
Technical Abstract: Recent outbreaks of Campylobacter mediated disease attributed to undercooked chicken livers have highlighted the continuing need for methods to reduce the Campylobacter numbers in these types of food products. In this study gamma irradiation is evaluated for its effectiveness in reducing Campylobacter jejuni numbers in experimentally contaminated chicken livers. A wide range of radiation doses were evaluated in conjunction with cold storage parameters both prior to and after the irradiation treatments. Freezing chicken livers prior to radiation treatment negatively impacted the effectiveness of irradiation in reducing C. jejuni numbers in the liver. Previously frozen livers exhibit D10 values of 0.748 KGy compared to livers not previously frozen which had a significantly lower D10 value of 0.361 KGy. Cold storage conditions post irradiation treatments at both 4 degs C and -20 degs C further reduced the C. jejuni numbers over those reduced by the initial irradiation. Of the combinations evaluated the largest reduction in C. jejuni numbers (3.8 logs) was achieved with 0.8 KGy of irradiation followed by 1 week storage at -20 degs C. However this reduction was not significantly different from the reduction (3.5 logs) produced by 0.8 KGy irradiation and only 48 hours of storage at -20 degs C.