Effect of Citral on the Thermal Inactivation of Escherichia coli O104:H4 in Ground Beef.

ABSTRACT: The objective of the present study was to analyze the combined effect of heat treatment (55 to 62.5°C) and citral (0 to 3%) on the heat resistance of Escherichia coli O104:H4 inoculated into ground beef. Inoculated meat packages were immersed in a circulating water bath stabilized at 55, 57.5, 60, or 62.5°C for various times. The surviving microbial cells were counted after culture on tryptic soy agar. A factorial design (4 × 4) was used to analyze the effects and interaction of heat treatment and citral. Heat and citral promoted E. coli O104:H4 thermal inactivation, suggesting a synergistic effect. At 55°C, the incorporation of citral at 1, 2, and 3% decreased D-values (control = 42.75 min) by 85, 89, and 91%, respectively (P < 0.05). A citral concentration-dependent effect (P < 0.05) also was noted at other evaluated temperatures. These findings could be of value to the food industry for designing a safe thermal process for inactivating E. coli O104:H4 in ground beef under similar thermal inactivation conditions.

Effects and interactions of gallic acid, eugenol and temperature on thermal inactivation of Salmonella spp. in ground chicken.

The combined effects of heating temperature (55 to 65°C), gallic acid (0 to 2.0%), and eugenol (0 to 2.0%) on thermal inactivation of Salmonella in ground chicken were assessed. Thermal death times were determined in bags submerged in a heated water bath maintained at various set temperatures, following a central composite design. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. D-values were analyzed by second-order response surface regression for temperature, gallic acid, and eugenol. The observed D-values for chicken with no gallic acid or eugenol at 55, 57.5, 60, 62.5, and 65°C were 21.85, 5.43, 2.83, 0.58, and 0.26min, respectively. A second-order polynomial model developed to inactivate Salmonella was found to be significant (p<0.0001) with a R2=0.95 and a no significant lack of fit (p>0.1073). Efficacy of the additives in increasing the sensitivity of the pathogen to heat was concentration dependent. The model developed in this study can be used by processors to design appropriate thermal process to inactivate Salmonella in chicken products used in the study and thereby, ensuring an adequate degree of protection against risks associated with the pathogen.

Modeling the effects of temperature, sodium chloride, and green tea and their interactions on the thermal inactivation of Listeria monocytogenes in turkey.

The interactive effects of heating temperature (55 to 65°C), sodium chloride (NaCl; 0 to 2%), and green tea 60% polyphenol extract (GTPE; 0 to 3%) on the heat resistance of a five-strain mixture of Listeria monocytogenes in ground turkey were determined. Thermal death times were quantified in bags that were submerged in a circulating water bath set at 55, 57, 60, 63, and 65°C. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. D-values were analyzed by second-order response surface regression for temperature, NaCl, and GTPE. The data indicated that all three factors interacted to affect the inactivation of the pathogen. The D-values for turkey with no NaCl or GTPE at 55, 57, 60, 63, and 65°C were 36.3, 20.8, 13.2, 4.1, and 2.9 min, respectively. Although NaCl exhibited a concentration-dependent protective effect against heat lethality on L. monocytogenes in turkey, addition of GTPE rendered the pathogen more sensitive to the lethal effect of heat. GTPE levels up to 1.5% interacted with NaCl and reduced the protective effect of NaCl on heat resistance of the pathogen. Food processors can use the predictive model to design an appropriate heat treatment that would inactivate L. monocytogenes in cooked turkey products without adversely affecting the quality of the product.