Evaluation of the hygienic performances of the processes for cleaning, dressing and cooling pig carcasses at eight packing plants

The hygienic performances of the processes for the production of cooled car casses at eight pork packing plants were assessed from small sets of microb iological data. At each plant, a single sample was obtained from a randomly selected site on each of 25 randomly selected carcasses at each of three s tages of processing, which were after polishing, after washing at the end o f the dressing process, and after cooling. The aerobic bacteria, coliforms and Escherichia coli recovered from each sample were enumerated. When bacte ria of one type were recovered from greater than or equal to 20 of 25 sampl es, the log mean number of those bacteria on the population of carcasses un dergoing processing was estimated on the assumption that the set of counts was normally distributed. The log of the total number recovered from 25 sam ples was calculated for each set of counts. The log mean numbers of total a erobic bacteria recovered from the polished carcasses at different plants r anged from about 1.9 to 3.8 log cfu cm(-2). At six of the plants, the log m ean numbers of total aerobes on the cooled carcasses did not differ substan tially from the log mean numbers on the polished carcasses, but the log mea n numbers on the cooled carcasses were substantially higher at one plant. a nd substantially lower at another than on the polished carcasses. Coliforms and E. coli were recovered from too few samples in most sets from cooled c arcasses for estimation of their log mean numbers. However, the log total n umbers of coliforms and E. coli recovered indicated that substantial number s of those organisms were added to carcasses during the dressing processes at four of the plants, and that the numbers on the carcasses were substanti ally reduced by the processes for cooling without spraying at two of the pl ants. At seven of the plants, the total numbers of coliforms and E. coli re covered from cooled carcasses were <3.1 and <2.2 log cfu 2500 cm(-2), respe ctively. The findings indicate that production processes for pig carcasses can be operated to give cooled carcasses with log mean numbers of total aer obes <2 cm(-2), and log total numbers of coliforms and E. coli each <1 2500 cm(-2). (C) 2000 Elsevier Science B.V. All rights reserved.