Comparison of Nitrite from Purified and Natural Sources on Inhibition of Clostridium perfringens Outgrowth during Cooling of Cured Turkey Breast According to FSIS Appendix B

Introduction:  USDA, FSIS Appendix B is widely used as a guideline for cooling meat and poultry products and allows extended cooling for products containing an ingoing minimum of 100 ppm NaNO₂.  Currently, however, products cured with nitrite from natural sources do not qualify for the same extended cooling.  The antimicrobial equivalency of nitrite from both purified and natural sources at comparable concentrations has not been evaluated during extended cooling following Appendix B. 

Purpose:  Compare the outgrowth of Clostridium perfringensduring a 15 h cooling curve in turkey breast cured with nitrite from purified and natural sources.

Methods:  Five treatments of deli-style turkey breast (74% moisture, pH 6.2-6.4, 1.4% NaCl) were prepared:  control (0 NaNO₂), 100 ppm NaNO₂ from both purified nitrite and pre-converted celery juice powder, 100 ppm purified nitrite + 547 ppm ascorbate, and 100 ppm pre-converted nitrite + 547 ppm ascorbate from cherry powder.  Treatments were inoculated with C. perfringens spores (three-strain mixture) to yield 3 log CFU/g.  Individual 50-g portions were vacuum-packaged, cooked to 71.1°C and cooled from 54.4°C to 26.7°C in 5 hours and 26.7°C to 7.2°C in 10 additional hours.  Triplicate samples were assayed for growth of C. perfringens at 0, 2.5, 5, 7.5, 10, 12.5, and 15 h by plating on tryptose-sulfite-cycloserine agar; experiments were replicated three times.

Results:  Control, purified nitrite, and pre-converted nitrite treatments showed > 1 log increase after 5 h and 5.3±0.2, 4.2±0.6, and 4.4±0.2 log increases at 15 h, respectively, revealing no difference in growth inhibition between the two nitrite sources and only slight inhibition by 100 ppm NaNO₂ relative to control.  In contrast, < 1 log growth was observed through 15 h in treatments containing 100 ppm nitrite and 547 ppm ascorbate. 

Significance:  This study confirmed that equivalent concentrations of nitrite, regardless of the source, provide similar inhibition of C. perfringens during cooling and suggests greater inhibition exists when combined with a cure accelerator.