Inactivation of Pathogenic Bacteria by Fd&c Red No. 3 and High-Pressure Processing Combination Treatment in Food Systems

Combinations of FD&C Red no. 3 and high-pressure processing (HPP) effectively inactivate various important processing-resistant spoilage and pathogenic bacteria in buffer; however, the lethality is unverified in food. The objective of this study was to determine the efficacy of HPP-Red 3 to inactivate Listeria monocytogenes and Escherichia coli O157:H7 in two food systems. Sterile carrot juice and turkey product were inoculated with stationary-phase cells and treated with HPP-Red 3. Red 3 concentrations of 10–100 ppm in carrot juice with HPP (500 MPa, 1 min, 23C) produced synergistic inactivation of L. monocytogenes. HPP-Red 3 (100 ppm) combinations in carrot juice caused synergistic inactivation of E. coli. HPP was ineffective at reducing L. monocytogenes in pre-cooked luncheon turkey product. HPP reduced E. coli in turkey product (3.9 log reduction); however, combination treatment did not significantly increase lethality, regardless of Red 3 concentration. Food systems significantly impact the efficacy of HPP-Red 3 against foodborne pathogens. PRACTICAL APPLICATIONS FD&C Red no. 3 is approved for use in most food products at levels up to 300 ppm to enhance the color of products. This colorant also possesses antimicrobial properties against gram-positive bacteria, due to the production of photooxidative species (superoxide, singlet oxygen, etc.). Interestingly, combining Red 3 with high-pressure processing (HPP) treatment produces synergistic inactivation of both gram-positive and gram-negative bacteria with and without light exposure (485 lux). Inclusion of Red 3 in product formulation and inclusion of HPP as a lethal processing step could be utilized by the food industry to enhance the shelf-life and safety of food products. Other certified food colorants could be used to adjust the color of the final product without altering the antimicrobial effect of the combination treatment. Efficacy of combination treatment needs to be validated for specific food systems.