Effect of dehairing operations on microbiological quality of swine carcasses

To develop a hazard analysis and critical control point plan for food processing operations, critical control points must be determined. Swine slaughtering and dressing operations were investigated to establish their critical control points. We monitored the microbiology of swine carcasses by surface swabbing carcass bellies at various steps during the process and by quantitating total aerobic plate count (APC) and coliforms. Starting with a dehaired carcass, the sequential steps monitored included presingeing, postsingeing, polishing, and chilling. Initial results indicate that singeing and chilling substantially reduced the levels of APC and coliforms, whereas polishing increased their levels. The hygienic characteristics of individual operations involved in dressing swine carcasses were then evaluated in the second experiment. A set of 40 randomly selected carcasses leaving singeer, polisher, shaver, and washer were sampled. Carcasses were heavily contaminated during the final polishing procedure, and the APC increased threefold compared with prepolishing levels. Washing reduced the bacterial numbers by 69%. To reduce the microbial load on swine carcasses, final polishing and manual shaving steps were not used during the dressing operation on a set of 90 carcasses. APCs on singed carcasses were reduced from 1.34 to -0.15 log10 CFU/cm2 when the final polisher and manual shavers were not used. However, carcasses were subsequently recontaminated with bacteria after evisceration, and the APCs were similar (P > 0.05) regardless of whether the final polishing and manual shaving steps were used, averaging 1.30 and 1.46 log10 CFU/cm2. These results indicated that individual operations can be identified as critical control points, appropriate limits can be set and monitored in a hazard analysis and critical control point system, and steps where further changes to reduce bacterial levels may be needed for swine slaughtering plants.