Microbial Progression in Sliced Vacuum Packaged Bacon at Refrigeration Temperatures

Abstract

Three hundred and forty eight strains of micro-organisms were isolated from packaged bacon which had been cured by one or other of 2 methods (A and B) and stored at &loo for 7 weeks. Before storage, Micrococcus sub-group 7 (47%) and corynefonn bacteria (33%) were the principal contaminants of bacon cured by method A and Micrococcus subgroup 1 (20%) and Microbacterium thermosphactum (21%), in bacon cured by method B. After 7 days at O", coagulase negative staphyIooocci accounted for 10 and 33% of the microflora in bacon A and B, respectively: other organisms were micrococci, 60% (A) and 25% (B); corynebacteria, 20% (A) and 12.5% (B), yeasts (ToruZopsis candida and T . dattila) 5% (A) and 29% (B). In the following month at loo, Micrococcus sub-group 5 was the dominant (43-88%) contaminant of bacon B; the incidence of Streptococcus Group N ranged from 27-36y0 and that of unidentified lactic acid bacteria from 23-32%. Towards the end of storage, the order of dominance was Micrococcus sub-group 3 (38-58%) and atypical streptobacteria (38%) in A; Streptococcus Group N (42%) and Gram positive rods ( 6 2 0 % ) in B. Staphylococci tended to die out during storage of bacons cured by the 2 methods and coagulase positive staphylococci were not isolated. THE MANY reports on the microbial changes which occur during storage of vacuum packed bacon (Ingram, 1960;Cavett, 1962Cavett, , 1963; Tonge, Baird-Parker & Cavett, 1964 ; Patterson, 1965) indicate that the microflora consists mainly of Xtaphylococcus, Micrococcus, lactobacilli, Xtreptococcus Group D, leuconostocs, and pediococci. Minor components of the microflora have rarely been discussed. This communication presents data on the major and minor components of the microflora of packaged bacon, the effect of 2 curing techniques on the types of micro-organisms, and the changes in the flora of bacon during refrigerated storage. Materials and MethodsBacon Cure method A Packs of bacon were taken randomly from the production line of a factory where de-fatted pork middles, from which the rind had been removed, were immersed for 10-15 sec in hot (98") brine [composition (g/l): NaC1, 200; NaN02, 1.11 with the aim of reducing contamination. A multi-needle injection apparatus (Anco Universal Supplies, Chicago) was used to inject a brine [containing (g/l): NaCl, 250; NaNO,, 1.5, NaNO,, 1; sodium ascorbate, 4-51. The injected meat was immersed for 2 days in freshly prepared brine [containing (g/l): NaCl, 260; NaNO,, 0.75; NaNO,, 1.51, L.5431

The Effect of Nitrate and Nitrite on the Microbial Flora of Wiltshire Bacon after Maturation and Vacuum‐packed Storage

“…Our results confirm previous findings that lactic acid bacteria and micrococci are the commonest bacteria on vacuum-packed bacon after storage below 25OC (Eddy & Gatherum 1961;Tonge et al 1964;Dempster 1973). There were, however, considerable differences in both the numbers and types of organisms on the fat and lean portions of the same bacon.…”

“…Tonge et al (1964) found that group D streptococci was the commonest type in their low-salt bacon after storage at 20° and 30 OC. Dempster (1973) studied two bacon samples during storage at 1 OC. Aciduric lactobacilli grew on bacon produced by a 'hygienic process', whereas group N streptotocci, non-aciduric lactobacilli and, to a lesser extent, group D streptococci were detected on a smoked 'sweet-cured bacon'.…”