DECONTAMINATION OF POULTRY PRODUCTS BY PULSED UV-LIGHT
Open Access
- Author:
- Keklik, Nene Meltem
- Graduate Program:
- Agricultural and Biological Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- August 21, 2009
- Committee Members:
- Ali Demirci, Dissertation Advisor/Co-Advisor
Ali Demirci, Committee Chair/Co-Chair
Virendra Puri, Committee Member
Paul Heinz Heinemann, Committee Member
Paul H Patterson, Committee Member - Keywords:
- decontamination
Listeria
Salmonella
poultry
pulsed UV light - Abstract:
- Poultry meat consumption has been increasing since the 1960s, and is estimated to grow fastest among livestock products until 2030. Low production costs and high nutritional value are the main reasons behind the popularity of poultry products. However, during processing, poultry carcasses are unavoidably exposed to bacterial contamination due to large bacterial load of the birds. Contamination risk of poultry increases with larger numbers of the birds and amount of poultry undergoing processing. Pulsed ultraviolet (UV)-light is an FDA-approved novel technology, which has the potential to inactivate microorganisms on food surfaces. The effectiveness of pulsed UV-light on microorganisms has been demonstrated by many researchers. Being a non-chemical, non-ionizing, and non-thermal (for short treatment time) process, pulsed UV-light may be a better alternative to decontaminate raw and/or minimally processed foods. Therefore, the efficacy of pulsed UV-light as a decontamination method for fresh poultry carcasses and products was evaluated in this research. Firstly, the effectiveness of pulsed UV-light was investigated for the surface decontamination of raw boneless chicken breast. The top surfaces of chicken breast samples were inoculated with an antibiotic-resistant strain of Salmonella Typhimurium. The artificially contaminated chicken breasts were then vacuum-packaged or remained unpackaged. Each unpackaged or vacuum-packaged sample was treated with pulsed UV-light for 5, 15, 30, 45, or 60 s at 5, 8, or 13 cm distance from the quartz window in a pulsed UV-light chamber. An input voltage of 3800 V and three pulses per second generated 5.6 J/cm2/pulse of radiant energy at the lamp surface. Based on the visual appearance of treated chicken breast pieces, the optimum treatment conditions were determined to be 5 cm-15 s for unpackaged samples and 5 cm-30 s for vacuum-packaged samples, both of which resulted in about 2 log10 CFU/cm2 reduction (~99%). The total energy and temperatures of samples increased with longer treatment time and shorter distance from the quartz window in the pulsed UV-light chamber. The changes in chemical quality and color of samples were determined after mild (13 cm; 5 s), moderate (8 cm; 30 s), and extreme (5 cm; 60 s) treatments. Neither malonaldehyde (MDA) content nor color parameters changed significantly (p>0.05) after mild or moderate treatments. Mechanical properties of the packaging material were analyzed before and after pulsed UV-light treatments. The elastic modulus both along and perpendicular-to-machine direction, and yield strength perpendicular-to-machine direction changed significantly (p<0.05) only after extreme treatment. In the second phase of the study, a pilot-scale pulsed UV-light continuous system was designed, built, and evaluated for its effectiveness on microbial load of whole chicken carcasses. The pulsed UV-light system consists of a total of four 16 in lamp housings facing each other in series, and a linear rail mounted along the midpoint of the chamber roof. Each chicken surface was inoculated with antibiotics-resistant Escherichia coli K12 inoculum and treated at the 5 cm distance from the quartz window of the lamp housing on each side. The treatment times of 30, 45, 60, 90, 120, and 180 s were selected, which correspond to the time each chicken would spend in one set of the systems. The log10 reductions ranged from 0.87 to 1.43 CFU/ml rinse solution after 30-s and 180-s treatments, which correspond to the actuator velocity of 78 and 13 cm/min, respectively. Energy levels for the lamps ranged from 0.24 to 0.25 J/pulse/cm2. Sample temperatures increased significantly (p<0.05) with longer treatment times; and ranged from 11.1 to 44.1 ¢ªC. CIELAB color parameters of carcasses after 45, 90, and 180-s treatments were determined. A significant (p<0.05) decrease in L* and increase in b* values were observed after 90-s and 180-s treatments, while a* values did not change significantly (p>0.05) after treatments. The optimum treatment time was identified as 45-s treatment, which resulted in ~1 log10 reduction (90% reduction). In the third phase of the study, the effectiveness of pulsed UV-light on the microbial load and quality of unpackaged and vacuum-packaged chicken frankfurters was investigated. Frankfurters were inoculated with Listeria monocytogenes Scott A on the top surfaces, and then treated with pulsed UV-light for 5, 15, 30, 45, and 60 seconds at 5, 8, and 13 cm distance from the quartz window in the pulsed UV-light chamber. Based on the visual appearance, the optimum treatment condition for both unpackaged and vacuum-packaged samples was identified as 60-s treatment at 8 cm, which resulted in about 1.6 and 1.5 log10 CFU/cm2 reductions (both ~97%), respectively. Temperature changes of samples and total energy (J/cm2) level increased with longer treatment time and shorter distance from the quartz window. Malonaldehyde (MDA) contents of samples did not change significantly (p>0.05) after mild (13 cm; 5-s) and moderate (8 cm; 30-s) treatments. Significant differences (p<0.05) in color parameters were observed after treatments of both unpackaged and packaged samples. Packaging material was also analyzed for mechanical properties. The elastic modulus, yield strength, percent elongation at yield point, maximum tensile strength, and percent elongation at break did not change significantly (p>0.05) after mild treatment. In the final phase of the study, the effectiveness of pulsed UV-light was evaluated for the decontamination of shell-eggs. Shell-eggs inoculated with antibiotic-resistant Salmonella Enteritidis on the top surface at the equator were treated with pulsed UV-light for 1-30 seconds at 9.5 and 14.5 cm from the UV-strobe in the pulsed UV-light chamber. A maximum log10 reduction of 7.7 (CFU/cm2) was obtained after 20-s treatment at 9.5 cm from the UV-lamp (at total dose of 23.6 J/cm2) without any visual damage to the egg. Temperatures of egg-shell surfaces and energy levels showed increases with longer treatment times and shorter distance from the UV-lamp. Pulsed UV-light treatments for 3, 10, and 20 s at either 9.5 or 14.5 cm did not change the albumen height, egg-shell strength or cuticle presence significantly (p>0.05). These results demonstrated that pulsed UV-light has potential to inactivate microorganisms on poultry products in both lab-scale and pilot-scale settings. The effect of pulsed UV-light on the shelf-life of poultry products as well as the ability of the light to penetrate into their surface still needs to be evaluated.