INACTIVATION OF SHIGA-TOXIN PRODUCING Escherichia coli (STEC) O157:H7 IN MILK BY COMBINED TREATMENT WITH HIGH HYDROSTATIC PRESSURE AND AQUEOUS POMEGRANATE EXTRACT

Robert Alvin Bernedo-Navarro Et Al

doi:10.15414/jmbfs.2016.6.1.636-640

Abstract

The aim of this work was to evaluate the synergistic effect of combined treatment with high hydrostatic pressure (HHP) and an aqueous extract of Punica granatum (pomegranate) peels on the survival of Shiga toxin-producing Escherichia coli (STEC). Our results showed that HHP (250 MPa, 60 min, 25 ºC) reduced the STEC bacterial load in milk and tryptic soy broth culture medium by about 2.5 and 3.5 logs, respectively. Under these conditions, HHP did not alter the cytotoxicity of Shiga toxins in Vero and human umbilical vein endothelial cells. Treatment with up to 30 mg of pomegranate extract/mL caused negligible inactivation, but a combination of HHP and pomegranate extract (3 mg/mL) produced bacterial inactivation from 109 CFU/mL to undetectable levels of viable bacteria. These findings suggest that a combination of HHP and pomegranate extract may be potentially effective in bacterial inactivation during food processing, particularly in the elimination of important foodborne pathogens such as STEC. a

Highlights

Shiga toxin-producing Escherichia coli (STEC) are important food and waterborne bacterial pathogens
The combination of high hydrostatic pressure (HHP) with pomegranate aqueous extract in tryptic soy broth (TSB) and milk contaminated with this pathogen resulted in total inactivation of the bacterial load (Fig 2)
Despite a low initial bacterial load of STEC O157:H7 in milk, this pathogen can grow during cheese processing to reach levels high enough to be considered a threat to human health (Montet et al, 2009)

Summary

Introduction

Shiga toxin-producing Escherichia coli (STEC) are important food and waterborne bacterial pathogens. Many cases of foodborne diseases worldwide are associated with the consumption of STEC-contaminated ground beef, water, raw milk, unpasteurized fruit juices, vegetables and other fresh produce (Yoon and Hovde, 2008; FDA, 2012). Non-thermal techniques, including high hydrostatic pressure (HHP), have received considerable interest from the food industry, with pressures of 100-1200 MPa being effective in the inactivation of a wide variety of microorganisms, including foodborne pathogens. Another important attribute of HHP is that this technique improves rennet or acid coagulation of milk with no detrimental effect on nutritional quality, flavor and texture (Chawla et al, 2011)

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