ASYMMETRIC DISTRIBUTION AND GROWTH OF BACTERIA IN SLICED VACUUM-PACKAGED HAM AND BOLOGNA

Commercially sliced vacuum-packaged cooked ham and bologna were found to contain significantly greater numbers of total and lactic acid bact eria (LAB) on package surface slices than on internal slices. This asy mmetric distribution persisted in most samples to beyond the manufactu rer's ''best before'' date. Enterobacteriaceae and bacterial spores we re detected infrequently. Bacterial spores were found most often on th e surface slices of commercially packaged sliced bologna. Where they o ccurred, aerobic and anaerobic sports were detected in equal numbers. Center slices of bologna were less hospitable sites for spores and LAB than were surface slices in vacuum packages. When freshly cooked ham and bologna were sliced together with uncooked fermented sausage, LAB from the sausage (pediococci and thermo-tolerant homofermentative lact obacilli) contaminated the cooked meats immediately causing an equal d istribution of bacteria throughout the slices. Pediococci did not surv ive in the vacuum-packaged cooked meats more than 2 weeks at 7 degrees C, The pH of co-sliced bologna prematurely dropped. The shelf life of refrigerated co-sliced ham was reduced by 44%, probably because of ad ventitious lactobacilli from the sausage. Brochothrix thermos-phacta w as not present in co-sliced or sliced control meats. Homofermentative lactobacilli predominated in co-sliced and control samples packaged in the laboratory, but in commercially packaged sliced cooked ham and bo logna heterofermentative LAB species were dominant, Prolonging cooked ham and bologna shelf life is possible if handling of uncooked ferment ed sausage is kept separate from the slicing and packaging of cooked c ured products.