Comparative Salmonella Spp. and Listeria monocytogenes Inactivation Rates in Four Commercial Mayonnaise Products

Abstract

Salmonella spp. and Listeria monocytogenes strains were inoculated into four commercial mayonnaise products: sandwich spread, real mayonnaise, reduced calorie mayonnaise dressing, and cholesterol-free reduced calorie mayonnaise dressing. Products represented a broad cross-section of aqueous phase acetic acid, salt, sucrose, and other compositional factors. Results showed that Salmonella spp. inactivation rates were unaffected by formula composition. The organism was rapidly inactivated, decreasing ≥8 log10 CFU/g in ≤72 h, in each of the four products. L. monocytogenes inactivation rates were directly correlated with aqueous phase acetic acid concentrations as follows: sandwich spread ≥ real mayonnaise > cholesterol-free reduced calorie mayonnaise dressing > reduced calorie mayonnaise dressing. L. monocytogenes inactivation rate in sandwich spread and real mayonnaise was similar to Salmonella spp. The reduced calorie mayonnaise dressings showed gradual, incremental population declines. L. monocytogenes decreased 3 and 5 log10 CFU/g in 72 h in reduced calorie and cholesterol-free reduced calorie mayonnaise dressings, respectively. The higher anti-listerial activity in the cholesterol free formulation was attributed to egg white lysozyme. This study documented that commercial mayonnaise, including reduced calorie mayonnaise dressing varieties, represent negligible consumer safety risks.