Internalization of Shiga Toxin-producing Escherichia coli in Beef Products as Influenced by Vacuum Marination

Introduction: Though successful in improving palatability, the risk of pathogen internalization propagated by vacuum-tumbled marination has been documented. As concerns regarding non-O157 Shiga toxin-producing E. coli serogroups rise—particularly those referred to as the “Big Six,” data regarding the internalization in marinated meat products is important. 

Purpose: The purpose of this study was to investigate the internalization and translocation of non-O157 and O157:H7 Shiga toxin-producing Escherichia coli in vacuum marinated beef products.

Methods: This study evaluated the marinade-mediated internalization and translocation of seven individual STEC serogroups (O157:H7, O26, O45, O103, O111, O121, and O145) in surface inoculated beef sirloin flaps. Beef bottom sirloin flaps were inoculated (10⁶ log CFU/cm²) with a multi-strain cocktail prior to vacuum tumbled marination (30 or 60 min) with a standard marination solution containing a food-grade dye and refrigerated storage (14 d). Pathogen presence and marinade migration after marination and storage were evaluated.

Results:  Data suggest that dye penetration was enhanced with vacuum storage for 14 d. Marination length had no influence on the immediate (d 0) internalization of STEC in sirloin beef flap sections, except for O145 (P = 0.03), which was greater after 60 min of tumbling. Marination for as little as 30 min resulted in approximately 10⁴ log CFU/g of internalized STEC, but, marination length did not influence (P > 0.05) the population of STEC present on the subprimal surface immediately after vacuum marination (d 0) or after 14 d of storage.

Significance: Marination length did not influence STEC attachment and had little influence on pathogen internalization; however, 30 min of vacuum marination resulted in substantial pathogen internalization. Likewise, increased marination length (60 vs. 30 min) increased (P < 0.05) the percentage of marinade uptake, regardless of inoculation serogroup.