Steam-Vacuum Treatment of Pig Carcass Surfaces

The aim of this study was to evaluate the efficiency of a steam-vacuum treatment of the surface of industrially slaughtered pig carcasses after evisceration but before chilling. Both the reduction of the microbial load after contamination with stomach contents, bile, or tubular rail fat and color changes of the carcass surface were investigated. Up to 25 samples per type of contamination were examined within an experimental setting under regular slaughterhouse conditions. The steam-vacuum treatment was applied on the approximately 30 cm long carcass rind between 2 and 8 s. This led to a statistically significant reduction (p < 0.0001) in total bacterial counts of up to 2 log₁₀ levels to values near or below the lower detection limit for all types of contamination considered (stomach contents (-1.2 log CFU/cm²) (p < 0.0001), bile (-1.6 log CFU/cm²) (p < 0.0001) and tubular fat (-2.2 log CFU/cm²) (p < 0.0001). Noncontaminated, nontreated carcasses underwent a color change of ΔE = 2.5 ± 1.2 (ΔE represents the overall color difference, where higher values indicate more noticeable color changes.) during storage of the carcass surface at 2 °C after 24 and 48 h. After steam-vacuum treatment, no statistically significant color differences (24 h storage: 2 s p = 0.7403, 4 s p = 0.8769, 6 s p = 0.1755, 8 s p = 0.0971; 48 h storage: 2 s p = 0.9710, 4 s p = 0.9967, 6 s p = 0.5648, 8 s p = 0.5360) were observed compared to untreated carcasses after storage (ΔE = 3.2 ± 1.3). Stomach content could be completely removed by the steam-vacuum treatment without affecting the color (48 h storage: 2 s p = 0.9704, 4 s p = 1.000, 6 s p = 1.000, 8 s p = 0.9996) compared with the control group. The color changes caused by bile (ΔE = 12.9 ± 4.12; p < 0.0001) and tubular rail fat (ΔE = 8 ± 3; p < 0.0001) could not be reversed completely by vacuum steam treatment. After contamination and decontamination, significant color differences remained in the b* (yellowness) range for bile (p < 0.0001) and in all three color ranges for tubular rail fat (p < 0.0001). Overall, steam-vacuum treatment appears to be a suitable microbiological decontamination method, as the microbial levels after treatment were below the detection limit.