Sensitizing processing-resistant foodborne spoilage and pathogenic bacteria to ultra-high pressure by food colorants
Creators:Waite, Joy G.
Advisor:Yousef, Ahmed E.
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Series/Report no.:Food Science and Technology. Graduate student poster competition, 2007
Treating foods with ultra-high pressure (UHP) causes significant inactivation of microbial load, however a small number of survivors are often observed after extreme pressure treatments (a tailing phenomenon). Consequently, it is important to identify conditions and additives that enhance the efficacy of pressure against foodborne pathogenic and spoilage microorganisms. Based on preliminary work, it was hypothesized that food colorants could be used in combination with UHP to enhance pressure lethality. The seven U.S. certified food colorants (FD&C Blue No. 1, Blue No. 2, Green No. 3, Red No. 3, Red No. 40, Yellow No. 5, and Yellow No. 6) were tested for synergy with UHP against Lactobacillus plantarum in citrate-phosphate buffer (pH 7.0). FD&C Red No. 3 was the only food colorant exhibited antimicrobial properties as well as enhancing UHP lethality. Further studies were performed using FD&C Red No. 3 against processing-resistant Listeria monocytogenes and Escherichia coli O157:H7 strains. Synergy of inactivation occurred with FD&C Red No. 3 concentrations as low as 3 ppm when the pathogens were treated with 400 MPa for 3 minutes. FD&C Red No. 3 (10 ppm) and UHP (400 MPa for 3 minutes) inactivated a large population (>7 log cfu/ml) of the processing-resistant L. monocytogenes OSY-328; UHP treatment alone inactivated ~0.3 log cfu/ml, whereas dye treatment alone inactivated 1.8 log cfu/ml. Gram-positive strains were sensitive to FD&C Red No. 3 alone, while E. coli O157:H7 was only affected when treated with the colorant in combination with UHP.
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