Inactivation of Toxoplasma gondii bradyzoites after salt exposure during preparation of dry cured hams

Authors: Fredericks, Jorrell; Hawkins Cooper, Diane; Hill, Dolores; Luchansky, John; Porto-Fett, Anna; Shoyer, Brad; Fournet, Valsin; Urban, Joseph; Dubey, Jitender

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2020
Publication Date: 5/21/2020
Citation: Fredericks, J.N., Hawkins Cooper, D.S., Hill, D.E., Luchansky, J.B., Porto Fett, A.C., Shoyer, B.A., Fournet, V.M., Urban Jr, J.F., Dubey, J.P. 2020. Inactivation of Toxoplasma gondii bradyzoites after salt exposure during preparation of dry cured hams. Journal of Food Protection. 83(6):1038-1042. https://doi.org/10.4315/0362-028X.JFP-19-461.
DOI: https://doi.org/10.4315/0362-028X.JFP-19-461

Interpretive Summary: Food products continue to be responsible for important outbreaks of disease in consumers. For example, the consumption of raw or undercooked pork has historically been linked to toxoplasmosis, a disease that occurs worldwide and is caused by the protozoan Toxoplasma gondii. Given the possibility of the presence of T. gondii in pork meat, the frequent use of pork for products not intended to be cooked before being eaten (ready-to-eat meats such as pepperoni) increases the potential risk for transmission of this parasite. Studies have demonstrated that T. gondii is killed in the initial stages of dry salt curing during the preparation of pepperoni sausages. In this study, we have investigated the the impact of the dry salt curing process during preparation of dry cured hams on time of killing of the parasite. This study demonstrated that the dry salt curing process kills T. gondii early in the curing process, such that properly prepared dry cured hams are safe for human consumption with respect to T. gondii.

Technical Abstract: Foodborne pathogens continue to pose a public health risk, resulting in significant outbreaks of disease in consumers. The U.S. Code of Federal Regulations (9 CFR 318.10) and recent guidance documents from the U.S. Food Safety and Inspection Service regulate curing methods to reduce exposure to viable Trichinella spiralis in meats, such as dry-cured hams, intended for consumption without cooking; but no specific tests are mandated for assessing viability of another foodborne parasitic threat to food safety, Toxoplasma gondii (T. gondii). Previous studies demonstrated that T. gondii is inactivated in the initial stages of dry curing during preparation of pepperoni sausage. In this study, we have investigated how soon T. gondii is inactivated in dry-cured whole hams processed using methods approved under existing U.S. Food Safety and Inspection Services regulatory standards. Pork hams that were shown to be infected with T. gondii via modified agglutination test (MATs) were salted/cured for 33 days at 3°C and 85 ± 5% relative humidity (RH), and then dried for up to 12 months at 12°C and 67.5 ± 2.5% RH. Inactivation of T. gondii was assessed by mouse bioassay and MATs. We found that T. gondii was inactivated during the salting/curing step (33 days); no viable T. gondii was detected in the mouse bioassay and MATs in any of the samples tested during the entire 12 months of the experiment. These results demonstrate that currently approved and validated protocols for production of dry cured hams in the U.S. are sufficient for inactivating T. gondii as a risk to consumers of this product.