Rapid inactivation of Toxoplasma gondii bradyzoites during formulation of dry cured ready-to-eat pork sausage

D.E Hill,J Luchansky,A Porto-Fett,H.R Gamble,V.M Fournet,D.S Hawkins-Cooper,J.F Urban,A.A Gajadhar,R Holley,V.K Juneja,J.P Dubey

doi:10.1016/j.fawpar.2018.e00029

Abstract

Curing processes for pork meat in the U.S. currently require individual validation of methods to demonstrate inactivation of Trichinella spiralis, a nematode parasite historically associated with pork. However, for protozoan parasites, no such strictures exist. It has been assumed, with little evidence, that curing processes required to inactivate Trichinella also inactivate Toxoplasma gondii. Currently no model of meat chemistry exists that can be correlated with inactivation of T. gondii. Given the possibility of the presence of T. gondii in pork meat, and the frequent use of pork for ready-to-eat (RTE) products not intended to be cooked, curing methods which inactivate T. gondii early in the curing process would be of great value to producers. In this study, we tested the effect of five variables – salt/brine concentration, water activity (aw), pH, temperature, and time on inactivation of T. gondii bradyzoites in tissue cysts using low and high endpoints for common curing treatments during preparation of dry cured pork sausage. Survival of T. gondii bradyzoites at each stage of preparation was assessed using a mouse bioassay. Results indicated that encysted T. gondii bradyzoites do not survive the early stages of the dry curing process within the endpoint parameters tested here, even at levels of NaCl that are lower than typically used for dry curing (1.3%). Exposure of T. gondii encysted bradyzoites to curing components in the formulated batter resulted in rapid inactivation of bradyzoites. These data suggest that the use of dry curing components may be effective for controlling T. gondii potentially transmitted through RTE meats, rendering them safe from risk with respect to T. gondii transmission to human consumers.

Highlights

Though curing processes have been used for centuries as a method to preserve meat products in a state that renders them microbiologically safe for human consumption in the absence of cooking, no dry curing processes have been validated for inactivation of protozoan parasites found in meat, such as Toxoplasma gondii
Five mice each were inoculated with 1 ml of digest material from 50 g samples of the 8 pepperoni batter formulations; all 5 mice were positive in 2 of the formulations; 4 of 5 mice were positive in 5 of the formulations; and 3 of 5 mice were positive in 1 formulation for T. gondii tissue cysts observed microscopically in brain squashes and by ELISA (Table 2)
Five mice each were inoculated with 1 ml of digest material from 50 g samples of the 8 pepperoni batter formulations at 3 h intervals during the fermentation process; 2 mice were positive in 1 of the formulations (1.3% NaCl, pH 4.6 endpoint) for T. gondii tissue cysts observed microscopically in brain squashes and by ELISA at the first 3 h interval; all subsequent tests for T. gondii tissue cysts in brain squashes and ELISA were negative in all batter formulations and at all 3 h intervals (Table 3)

Summary

Introduction

Though curing processes have been used for centuries as a method to preserve meat products in a state that renders them microbiologically safe for human consumption in the absence of cooking, no dry curing processes have been validated for inactivation of protozoan parasites found in meat, such as Toxoplasma gondii. Using the newly developed inactivation data, existing and newly developed curing process that fall within the tested parameters can be assessed for risk mitigation with respect to T. gondii based on the meat chemistry of the final product. These data provide a baseline for the ultimate goal of developing a searchable T. gondii inactivation model which can be used to populate the USDA, ARS Pathogen Modeling Program These data provide a baseline for the ultimate goal of developing a searchable T. gondii inactivation model which can be used to populate the USDA, ARS Pathogen Modeling Program (PMP; download at https://www. ars.usda.gov/northeast-area/wyndmoor-pa/eastern-regional-research-center/residue-chemistry-and-predictive-microbiologyresearch/docs/pathogen-modeling-program/pathogen-modeling-program-v ersion-70-installation/) and used by producers and regulators to assess the safety of new curing processes without the need for individual process validation

Methods

Results

Conclusion