Synergistic Effect of Propolis and Heat Treatment Leading to Increased Injury to E scherichia coli O157:H7 in Ground Pork

Abstract

This study was conducted to determine the thermal inactivation of Escherichia coli O157:H7 in the presence of propolis in culture and in ground pork. Overnight cultures (∼106 cfu/mL) or inoculated ground pork (1.0 g, ∼106 cfu/g) were heat treated at 57, 60 and 63 ± 0.1C for predetermined times. The surviving cell populations were enumerated on appropriate media, from which D and z values were determined. The D values for E. coli O157:H7 in broth were 7.33 ± 1.33, 1.34 ± 0.29 and 0.85 ± 0.04 min, respectively (z = 6.4C), whereas in the presence of propolis (8.98 mg/mL), the D values were 0.53 ± 0.02, 0.25 ± 0.00 and 0.17 ± 0.00 min (z = 10.3C). For ground pork, the D values of E. coli O157:H7 were 4.88 ± 0.23, 0.77 ± 0.00 and 0.37 ± 0.00 min, respectively (z = 5.4C), whereas the D values in the presence of propolis (35.92 mg/g) were 2.98 ± 0.02, 0.46 ± 0.03 and 0.26 ± 0.02 min (z = 5.5C). Thermal injury was more pronounced in the presence of propolis at all temperatures. These data suggest that propolis and heat treatment may have a synergistic effect that could have potential applications in the case of meat products. Practical Applications The addition of propolis to Escherichia coli in broth and meat rendered the pathogen more sensitive to the lethal effects of heat at all temperatures, resulting in smaller D values than those obtained with E. coli heat treated alone in both culture and meat samples. These data suggest that propolis and heat treatment may have a synergistic effect that could have potential applications for meat products.