Influence of Certain Processing Steps on Attachment of Microorganisms to Pork Skin1

Abstract

Pseudomonas putrefaciens and lactobacillus counts of inoculated pork skin obtained with the maceration method usually were higher than were those obtained with the rinse method. Scalding and dehairing and shaving caused extensive destruction of the test organisms when placed on the skin before these slaughter-dressing steps. Smaller decreases in count occurred during singeing and washing and during evisceration and washing. Increases in S value (log count by maceration method minus log count by rinse method) for P. putrefaciens and a Lactobacillus sp. after freezing-thawing of inoculated pork skin may be related to a higher death rate of bacteria in the water film than for those entrapped in skin crevices. P. putrefaciens and the Lactobacillus sp. that were attached to pork skin exhibited greater heat resistance than did those bacteria which were not attached to skin. During storage of inoculated pork skin, S values of P. putrefaciens and the Lactobacillus sp. increased; this increase probably reflects increased strength of attachment of bacteria to the skin. Scanning electron microscopy of inoculated pork skin showed the formation of extracellular structures which may play a role in attachment of bacteria to skin or meat surfaces.