Location: Animal Parasitic Diseases Laboratory
Project Number: 8042-32000-101-20-R
Project Type: Reimbursable
Start Date: May 1, 2014
End Date: Nov 1, 2015
This study will determine if a model of five parameters of curing can be developed that will reliably predict inactivation of two foodborne pathogens, Trichinella spiralis and Toxoplasma gondii. If so, these parameters can be extrapolated to various curing processes and will reduce or eliminate the need for individual product validation.
Curing processes currently require individual validation of methods to demonstrate inactivation of Trichinella spiralis. This is a major undertaking for each process; currently no model of meat chemistry exists that can be correlated with inactivation of Trichinella or Toxoplasma. Development of the curing model will be conducted following experimental design protocols that have been successfully used in the Agricultural Research Service’s Pathogen Modeling Program. Participants involved in the modeling phase include ARS scientists and collaborators, scientists from the Canadian Food Inspection Agency, and faculty at the University of Manitoba (Department of Food Science). A multi-factorial design for curing parameters will be developed in consultation with scientists from ARS, Eastern Regional Research Center where the Pathogen Modeling Program was developed. Using low and high endpoints for common curing treatments, it is anticipated that a minimum of three replicates of 27 to 54 combinations to populate the model will be needed. For the experimental modeling phase, 20 pigs each for Trichinella and Toxoplasma, will be infected at levels consistent with natural infections. Pigs will be grown to near market size, slaughtered and infected muscle tissue will be collected. Meat will be ground, mixed with fat (~17%) and salt, starter culture, dextrose/sugar, and cure (sodium nitrate/nitrite). Product will be mechanically extruded into 55 mm diameter casing to form sausages of approximately 500 g each. Sample product will be placed in a laboratory environmental drying chamber and subjected to an environment for fermentation to achieve pH values from 4.8 to 5.3. Once the targeted pH is achieved, samples will be dried until the target aw of between 0.86 and 0.92 is met. During curing, temperature and pH will be monitored daily while salt concentration, aw, and residual nitrite will be determined by standard methods and monitored weekly. Each cured endpoint sample will be subjected to bioassay to determine the viability of Trichinella and Toxoplasma. Bioassay in rats (Trichinella) and cats (Toxoplasma) will be performed by a combination of tissue digestion, oral inoculation, and microscopic examination of tissues and feces for parasites. Meat chemistry and viability data will be incorporated into the framework of the Pathogen Modeling Program and a predictive model will be developed that can be used in validation studies.