Inactivation of Shiga Toxin-Producing Escherichia coli in Veal Using High Pressure Processing, Gamma Radiation, and Ultraviolet Light

Introduction: Shiga Toxin-producing Escherichia coli (STEC) are common contaminants in meat and are responsible for numerous foodborne illness outbreaks and product recalls. Recently, veal has received attention from regulatory agencies due to possible contamination with STEC.

Purpose: The purpose of this study was to determine the inactivation kinetics of STEC  in veal using non-thermal process interventions including high pressure processing (HPP), gamma radiation (GR), and ultraviolet light (UV-C).  

Methods: An eight-isolate cocktail (Big Six, O104, O157:H7) STEC was inoculated (10⁸ CFU/g) into veal, treated with the non-thermal process interventions, and the STEC recovered using E. coli Petrifilms.

Results: When the STEC cocktail was suspended in 95% lean ground veal and irradiated (0 - 1.8 kGy, 5°C) the D-10 was 0.39 kGy. When the STEC cocktail was inoculated in the ground veal and subjected to HPP (450 mPa, 0-30 min, 5°C) the D-10 was 5.69 min. The ability of the STEC cocktail to grow in ground veal following treatment with GR (1.8 kGy) and HPP (450 MPa, 30 min) during storage (10°C, 14 d) was examined. The STEC were able to grow ca. 2 log in the untreated veal, but were unable to grow in the HPP and GR treated veal. When the STEC cocktail was surface-inoculated onto veal cutlets and subjected to UV-C (5 mW/cm², 0 - 2.0 J/cm², 5°C), ca 1.5 log was inactivated.  When the ability of UV-C to inactivate the STEC suspended in veal purge inoculated onto food grade high density polyethylene and stainless steel surfaces was examined, ca. 4 log (0.5 J/cm²) and 6 log (1.0 J/cm²) reductions were observed.

Significance: This indicates these non-thermal process interventions, which do not require the use of exogenous water or chemicals to inactivate microorganisms, can inactivate STEC in veal products, therefore reducing the risk of foodborne illness to consumers.