The effect of hot‐water immersions on the appearance and microbiological quality of skin‐on chicken‐breast pieces

Summary Immersion in hot water is one of many potential methods for reducing levels of pathogenic bacteria on the surface of poultry meat. However, if the meat is to be sold in the raw state reductions in microbiological numbers need to be achieved without changing the appearance of the meat. Samples of vacuum-packed skin-on chicken breast were immersed in hot water for a range of temperatures and times. Samples were then water cooled to arrest further heating. The final appearance of the samples was assessed visually and instrumentally with a chroma meter. Surface and internal temperatures were also measured. From this series of initial experiments a range of maximum temperature–time treatments were identified that would not cause unacceptable changes to surface appearance. Microbiological tests were then conducted on samples inoculated with a nalidixic acid resistant strain of Escherichia coli serotype O80 subjected to these treatments. The results showed that determining changes to the appearance of skin from samples by using a chroma meter was difficult. The changes caused to the samples by heat treatment were initially textural rather than colourimetric and thus could be identified visually but not instrumentally with a chroma meter. Visual changes were found for immersion times greater than 120 s at 50 °C, 60 s at 60 °C, 9 s at 70 °C, 6 s at 80 °C, 2 s at 90 °C and 1 s at 100 °C. The average temperatures measured on the surface after 2 s immersion at 90 °C and after 60 s at 60 °C were 20.5 °C and 54.8 °C, respectively. No reductions in counts of E. coli serotype O80 were measured on samples treated under these conditions. The results indicate that there is no immersion heat treatment (below 90 °C) capable of reducing contamination with E. coli, or similar thermotolerant microorganisms, on poultry without causing adverse changes in the product.