Chicken fillets subjected to UV-C and pulsed UV light: Reduction of pathogenic and spoilage bacteria, and changes in sensory quality

Abstract

We have compared the efficacy of continuous ultraviolet (UV-C) (254 nm) and pulsed UV light in reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, Staphylococcus aureus, enterohemorrhagic Escherichia coli, Pseudomonas spp., Brochothrix thermospacta, Carnobacterium divergens, and extended-spectrum β-lactamase producing E. coli inoculated on chicken fillet surface. Fluences from 0.05 to 3.0 J/cm² (10 mW/cm², from 5 to 300 s) used for UV-C light resulted in average reductions from 1.1 to 2.8 log cfu/cm². For pulsed UV light, fluences from 1.25 to 18.0 J/cm² gave average reductions from 0.9 to 3.0 log cfu/cm². A small change in the odor characterized as sunburnt and increased concentration of volatile compounds associated with burnt odor posed restrictions on the upper limit of UV treatment, however no sensory changes were observed after cooking the meat. Treatments under modified atmosphere conditions using a UV permeable top film gave similar or slightly lower bacterial reductions.

Practical applications: Ultraviolet (UV) light may be used for decontaminating the surface of food products and reduce viability of pathogenic and spoilage bacteria. Exposure of raw chicken fillet surface to various doses of continuous UV-C or pulsed UV light proposed in the present work represent alternatives for microbiological improvement of this product. Chicken fillets can be treated in intact packages covered with UV permeable top film, thus avoiding recontamination of the meat. UV-C light treatment is a low cost strategy with low maintenance, whereas pulsed UV light involves more elaborate equipment, but treatment times are short and less space is required. Both methods can be helpful for producers to manage the safety and quality of chicken fillets.

Figure 1

Flowchart illustrating the experimental set‐up. Reduction of bacteria on skinless chicken fillets using UV light treatments (a), and sensory analyses of chicken fillets treated with UV light (b). Chicken fillets inoculated with pathogens and bacteria often found as natural contaminants on fresh chicken meat were exposed to different UV light treatments in air, representing unpackaged chicken, and for two selected species on modified atmosphere packaged (MAP)‐chicken. The bacterial species are listed in Table 1. Sensory analyses of chicken fillets with no added bacteria were conducted after UV light treatments of both unpackaged chicken and MAP‐chicken

Figure 2

Reductions of (a) S. Enteritidis, (b) L. monocytogenes, (c) S. aureus, (d) enterohemorrhagic E. coli (EHEC), (e) Pseudomonas spp., (f) B. thermospacta, (g) C. divergens, and (h) ESBL‐producing E. coli on chicken fillet meat after continuous UV‐C (white bars) and pulsed UV light (grey bars) exposures at different fluences (J/cm²). The chicken samples were treated in air, representing unpackaged chicken. Three separate ANOVA were performed for each species, represented by upper case letters (comparing UV‐C and pulsed UV light treatments), numbers (comparing UV‐C light treatments) and lower case letters (comparing pulsed UV light treatments). Samples containing the same letter/number were not considered different

Figure 3

Reductions of (a) C. divergens and (b) ESBL‐producing E. coli on MAP‐chicken exposed to continuous UV‐C (white bars) and pulsed UV light (grey bars) at different fluences (J/cm²). A gas mixture of 60% CO₂ and 40% N₂ and a UV permeable top film was used for the packages. Three separate ANOVA were performed for each species, represented by upper case letters (comparing UV‐C and pulsed UV light treatments), numbers (comparing UV‐C light treatments) and lower case letters (comparing pulsed UV light treatments). Samples containing the same letter/number were not considered different

Figure 4

Weibull models for bacterial log reduction as a function of UV exposure. Models for each species (black continuous line) and common models (red dotted line) are shown for bacterial reduction on unpackaged chicken fillet meat after (a) continuous UV‐C and (b) pulsed UV light exposures at different fluences (J/cm²)

Figure 5

Sensory analysis of (a) raw chicken fillet samples and (b) cooked chicken fillet samples. Chicken samples were exposed to continuous UV‐C light at 10 mW/cm² for 10 s (UVC‐10) and 60 s (UVC‐60), giving fluences of 0.1 J/cm² and 0.60 J/cm², respectively, and pulsed UV light to a low pulse with fluence of 1.25 J/cm² (PUV‐L) and three times to a high pulse giving a fluence of 10.8 J/cm² (PUV‐Hx3), both in air (O₂) and anaerobic (CO₂ : N₂) atmospheres, representing unpackaged chicken and MAP‐chicken, respectively. The intensities of different odors of raw samples and odor/taste/flavor of cooked samples were registered, 1 = no intensity and 9 = high intensity. The letters above the columns indicate grouping according to ANOVA and Tukey multiple comparison test. Samples with the same letter are considered being equal for the specific property

Figure 6

Volatile organic compounds from chicken which showed an increase in concentration (pg/g) as a result of exposure to UV light. The samples included were chicken exposed to pulsed UV light at low intensity at fluence 1.25 J/cm² (PUV‐L) treated under anaerobic (CO₂:N₂) atmosphere (MAP‐chicken), an untreated control (Untreated), chicken exposed to UV‐C light at 10 mW/cm² for 60 s (UVC‐60) giving a fluence of 0.60 J/cm² and pulsed UV light three times at high intensity (PUV‐Hx3) giving a fluence of 10.8 J/cm² treated in air (O₂). The precision of replicate measurements were within 15%