Comparison of Nitrite Derived from Natural and Synthetic Sources on the Inhibition of Clostridium perfringens during Extended Cooling of Turkey Breast

Introduction: Natural and organic processed meats cured with vegetable juice powder as an alternative to synthetic NaNO₂ typically have lower nitrite levels than traditional products and hence have lower ability to inhibit pathogens such as Clostridia.  However, the antimicrobial activity of nitrite from the two sources has not been compared when added at equivalent levels.

Purpose: To compare the inhibition of Clostridium perfringens during extended cooling of turkey breast cured with cultured celery juice powder vs. NaNO_2.

Methods: Seven treatments of deli-style turkey breast (76% moisture, pH 6.1-6.3, 1.4-1.5% NaCl) were prepared with 0, 40, 80, or 120 ppm nitrite derived from cultured celery powder or synthetic NaNO₂, and inoculated with C. perfringens spores (three-strain mixture) to yield 3-log CFU/g.  Individual 100-g portions were vacuum-packaged, cooked to 71.1°C and cooled to 4°C during a 10-hour linear cooling protocol. Triplicate samples were assayed for populations of C. perfringens by plating on tryptose-sulfite-cycloserine at 0, 2.5, 5, 7.5 and 10 h; experiments were replicated three times. 

Results: Control samples (0 ppm NO₂) without antimicrobial supported an average 1.8, 2.9 and 3.6 log increase of C. perfringens at 5, 7.5 and 10 hours, respectively. Addition of 40 ppm NO₂ derived from either source, but without cure accelerator, had no additional inhibition compared to the control.  Inhibition was not significantly different between the two 80 ppm NO₂ treatments with an average 0.8, 1.9, and 1.9 log increase at 5, 7.5 and 10 hours, respectively. Both 120 ppm NO₂ inhibited growth to < 1-log increase during the 10 hour cooling.

Significance: This study confirmed that the concentration of NO₂, rather than source, is the primary factor in the inhibition of C. perfringens during the extended cooling of meats.  Additional studies should be completed to determine the effect of cure accelerators and nitrite from a natural source during extended cooling.