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.