Combination of ultra-high pressure and xanthene-derivatives to inactivate food-borne spoilage and pathogenic bacteria

by Waite, Joy Gail

Abstract (Summary)
Food processing methods designed to produce safe food occassionally lead to development of processing-resistant spoilage and pathogenic microorganisms. Thus, inactivation of these potentially problematic bacterial strains by combinations of physical and/or chemical treatments requires thorough investigation. Previous studies have shown antimicrobial peptides, oxidants, and phenolic compounds to enhance the efficiency of emerging processing methods, such as ultra-high pressure (UHP). The current study investigates the use of UHP in combination with hydroxyxanthenes, including FD&C Red No. 3, to inactivate pressure-resistant strains of Lactobacillus plantarum, Listeria monocytogenes, and Escherichia coli O157:H7. Combination treatments of UHP (400 MPa, 3 minutes) and Red No. 3 (3 to 10 ppm) resulted in synergistic inactivation of pressure-resistant bacterial strains. Red No. 3 is a known photosensitizer and led to inactivation of Gram-positive species with short exposure to ambient light (15-30 minutes); however this compound was ineffective against Gram-negative species without UHP. Irreversible changes in the barrier properties of the outer membrane occurs with UHP >250 MPa leading to accumulation of Red No. 3 and cell inactivation. Inactivation of Gram-positive and Gram-negative species by combination treatment was light-dependent with low UHP treatments (<400 MPa), indicating a role of photooxidation. With increasing pressures (>400 MPa) a light-independent mechanism was identified. Efficacy of light-dependent and light-independent inactivation was determined in two food systems: carrot juice and turkey meat product. Combination treatment was effective against L. monocytogenes and E. coli O157:H7 in carrot juice with Red No. 3 at concentrations of 10 to 100 ppm. These strains were resistant to inactivation by combination treatment in turkey meat product, indicating that specific food components or composition may decrease the efficacy of these treatments. Pressure-resistant strains were treated with UHP alone or UHP-Red No. 3 combinations under aerobic and anaerobic conditions to determine the impact of type I and type II photooxidation. Inactivation by combination treatment with light exposure is primarily due to type I photooxidation. Interestingly, inactivation without light exposure was oxygen dependent for all microorganisms tested. In conclusion, inactivation of UHP processing-resistant microorganisms can be achieved using UHP-Red No. 3 combinations in food systems.
Bibliographical Information:


School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:ultra high pressure food microbiology xanthene derivatives colorants escherichia coli o157 h7 listeria monocytogenes lactobacillus plantarum


Date of Publication:01/01/2007

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