Combined steam and ultrasound treatment of broilers at slaughter: a promising intervention to significantly reduce numbers of naturally occurring campylobacters on carcasses.

Steam or hot water decontamination treatment of broiler carcasses is hampered by process limitations due to prolonged treatment times and adverse changes to the epidermis. In this study, a combination of steam with ultrasound (SonoSteam®) was investigated on naturally contaminated broilers that were processed at conventional slaughter speeds of 8,500 birds per hour in a Danish broiler plant. Industrial-scale SonoSteam equipment was installed in the evisceration room, before the inside/outside carcass washer. The SonoSteam treatment was evaluated in two separate trials performed on two different dates. Numbers of naturally occurring Campylobacter spp. and TVC were determined from paired samples of skin excised from opposite sides of the breast of the same carcass, before and after treatments. Sampling was performed at two different points on the line: i) before and after the SonoSteam treatment and ii) before the SonoSteam treatment and after 80 min of air chilling. A total of 44 carcasses were examined in the two trials. Results from the first trial showed that the mean initial Campylobacter contamination level of 2.35 log10 CFU was significantly reduced (n=12, p<0.001) to 1.40 log10 CFU after treatment. A significant reduction (n=11, p<0.001) was also observed with samples analyzed before SonoSteam treatment (2.64 log10 CFU) and after air chilling (1.44 log10 CFU). In the second trial, significant reductions (n=10, p<0.05) were obtained for carcasses analyzed before (mean level of 2.23 log10 CFU) and after the treatment (mean level of 1.36 log10 CFU). Significant reductions (n=11, p<0.01) were also found for Campylobacter numbers analyzed before the SonoSteam treatment (2.02 log10 CFU) and after the air chilling treatment (1.37 log10 CFU). The effect of air chilling without SonoSteam treatment was determined using 12 carcasses pre- and postchill. Results showed insignificant reductions of 0.09 log10 from a mean initial level of 2.19 log10 CFU. Numbers of TVC before treatments ranged between 3.47 and 4.79 log10 CFU. In all cases, TVC was significantly (p<0.001, n=45 in each trial) reduced by approximately 0.7 log10 CFU. An authorized sensory panel at the Danish Veterinary and Food Administration concluded that broiler carcasses treated with SonoSteam were acceptable for purchase. These conclusions were based on organoleptic differences (smell, skin/meat consistency, texture and color) of treated vs. untreated carcasses. Results obtained from this study suggest that steam-ultrasound treatment of carcasses at broiler processing plants can significantly reduce numbers of Campylobacter on naturally contaminated broilers.

Inactivation of pathogens on pork by steam-ultrasound treatment.

The objective of the study was to evaluate a new pathogen inactivation concept that combines application of pressurized steam simultaneously with high-power ultrasound through a series of nozzles. On skin and meat surfaces of pork jowl samples, counts of total viable bacteria were reduced by 1.1 log CFU/cm(2) after treatment for 1 s and by 3.3 log CFU/cm(2) after treatment for 4 s. The mean reduction of 1.7 to 3.3 log CFU/cm(2) on the skin surface was significantly higher than the reduction of 1.1 to 2.5 log CFU/cm(2) on the meat surface. The inactivation of Salmonella Typhimurium, Salmonella Derby, Salmonella Infantis, Yersinia enterocolitica, and a nonpathogenic Escherichia coli was studied on inoculated samples that were treated for 0.5 to 2.0 s. With one exception, no significant differences in reduction were observed among the bacterial types. After treatment for 0.5 s, the 0.9-to 1.5-log reductions of E. coli were significantly higher than the 0.4- to 1.1-log reductions for Salmonella and Y. enterocolitica. Overall, reductions increased by increasing treatment time; reductions were 0.4 to 1.5 log CFU/cm(2) after treatment for 0.5 s and 2.0 to 3.6 log CFU/cm(2) after treatment for 2 s. Reductions on the skin (1 to 3.6 log CFU/cm(2)) were significantly higher than reductions on the meat surface (1 to 2.5 log CFU/cm(2)). The reduced effect on the meat surface may be explained by greater protection of bacteria in deep structures at the muscle surface. No significant difference in reduction was observed between samples inoculated with 10(4) CFU/cm(2) and those inoculated with 10(7) CFU/cm(2), and cold storage of samples for 24 h at 5°C after steam-ultrasound treatment did not lead to changes in recovery of bacteria.