Date of Award

8-2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Food Technology

Advisor

Dawson, Paul L

Abstract

Food safety can be improved by various antimicrobial applications through the effective inhibition of microorganisms for certain periods by controlled release. Antimicrobials in powders and films were studied to investigate their activities and properties. Nisin (Nisaplin®) (200, 400, 600, 800, and 1000 IU/ml) was adsorbed to silica and different corn starches and their antimicrobial activities against Listeria monocytogenes were evaluated by agar diffusion assay. Nisin-adsorbed silica (Celpure P-65) powder had the highest antimicrobial activity at 600 IU/ml and also confirmed that the highest amount of nisin was adsorbed onto silica at the same concentration. Efficacy of both unmodified corn starch and modified corn starch for adsorption of nisin was less than that of silica due to low retained activity onto powder and much loss activity in supernatant during nisin-adsorbed powder processing. Nisaplin® and Guardian® incorporated gelatin films were evaluated for their film properties, and antimicrobial activities against Listeria monocytogenes in liquid media, solid media and ready-to-eat turkey bologna. As antimicrobial concentrations increased in films, intensity of yellowness increased and lightness decreased. Also, film tensile strength was reduced and elongation increased. Both oxygen permeability (OP) and water vapor permeability (WVP) of gelatin-based Nisaplin® films increased as antimicrobial concentration increased. OP of gelatin-based Guardian® films increased as level of incorporated antimicrobial increased while WVP decreased. Gelatin-based Nisaplin® films (0.025 ~ 0.5%) completely inhibited Listeria monocytogenes within 6 hours. Gelatin-based Guardian® films (0.5 ~ 3%) inhibited Listeria monocytogenes in liquid media and two lower concentrations (0.5% and 1%) were more effective at inhibiting Listeria monocytogenes than two higher concentration (2% and 3%). Antimicrobial activity of both films against Listeria monocytogenes on solid media were evaluated for 16 weeks and gelatin-based Guardian® films were more stable than gelatin-based Nisaplin® films. Both antimicrobial films effectively inhibited Listeria monocytogenes on bologna at 4℃ for 56 days. Gelatin films containing trans-2-dodecenal were developed and their antimicrobial activities against Listeria monocytogenes and Escherichia coli O157:H7 were evaluated in model system using peptone solution and turkey bologna. Also, film properties were evaluated. Trans-2-dodecenal gelatin films completely inhibited Listeria monocytogenes in 0.1% peptone solution within 8 hours. Also, this film reduced E. coli O157:H7 populations for 48 hours compared to control. Total color difference (∆E) of all treatments inoculated with Listeria monocytogenes increased during storage at 4℃ for 56 days. Films inoculated with E. coli O157:H7 also showed increased ∆E as storage time increased while there was no change in bologna from day 1 to 56 and ∆E was higher in order as follow 2% TD > 1% TD > Control > Bologna. Trans-2-dodecenal impregnated gelatin film suppressed Listeria monocytogenes and E. coli O157:H7 on bologna pieces during storage at 4℃ for 56 days. Antimicrobial activity of films against Listeria monocytogenes was more effective than activity against E. coli O157:H7.

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Food Science Commons

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