Evaluation of Vinegar against Listeria monocytogenes in Ready-to-Eat (RTE) Deli Ham Stored at 4°C

Introduction: Consumption of RTE meat and poultry products contaminated with L. monocytogenes has been related to different foodborne outbreaks. Intervention methods to control L. monocytogenes in deli meats exposed to the environment are needed to reduce the risk of foodborne illnesses. Consumer demand for natural antimicrobials is increasing.  Verdad® N8 and Verdad® N9 are liquid vinegars based on fermentation that can provide necessary antimicrobial performance to control the outgrowth of L. monocytogenes in RTE meat and poultry products.

Purpose: The objective is to validate the efficacy of Verdad® N8 and N9 against L. monocytogenes in RTE deli ham products stored at 4°C.

Methods: RTE ham formulation contained lean, inside and outside muscles, water (24.12%), salt (1.8%), sugar (1.7%), sodium phosphate (0.4%), sodium erythorbate (0.055%), sodium nitrite (0.250%), carrageenan (0.250%) and antimicrobial at different levels. RTE ham was sliced, inoculated with a five-strain Listeria monocytogenes cocktail at ca. 2.50 log CFU/g, vacuum packed and stored at 4°C for 120 days.  Twenty-five g samples were homogenized in 0.1% peptone water and plated out onto MOX agar. Plates were incubated at 35°C for 48 h and typical L. monocytogenes colonies were counted.

Results: Ham control samples had the fastest Listeria monocytogenes growth reaching 7.98 log CFU/g at the 25^th day of storage. All tested concentrations of Verdad^® N8 (2.10%) and Verdad®  N9 (2.64%) resulted in < 1 log CFU/g outgrowth of L. monocytogenes over the shelf life (120 days).

Significance: This research substantiates the antimicrobial performance of Verdad® N8 and Verdad® N9 against L. monocytogenes in RTE deli ham. The research provides meat industry with natural antimicrobials for ensuring food safety of RTE meat products.