Heat injury and recovery of Streptococcus faecium associated with the souring of chub‐packed luncheon meat

Abstract

The presence of NaCl in the heating medium provided some protection from lethal heat damage for cells of a Streptococcus faecium strain isolated from luncheon meat whereas the presence of NaNO2 either alone or in addition to NaCl, had no significant effect on cell survival. Subsequent recovery and growth of heat-damaged cells was retarded by the presence of NaCl. When NaNO2 was present in addition to NaCl the inhibitory effect of the latter was reduced. These principal components of the luncheon-meat-cure are apparently opposed in their activities on post-heating recovery and growth of Strep. faecium. Product stability, i.e. duration of the lag before growth occurs, is directly related to the severity of the heat treatment and to the concentration of NaCl in the product. Therefore the resistance of pasteurized chub-packed luncheon meat to streptococcal spoilage during storage at temperatures conducive to microbial growth results from a prolonged heat-induced salt-maintained pre-growth adjustment phase rather than to any inherent inhibitory property of the luncheon meat to the growth of non-heat-damaged Strep. faecium cells.

The death and lysis of microorganisms in environmental processes

“…although it was originally intended that the use of such media should be for the isolation and growth characterisation of microbes. Despite the repeated and often vehement criticism which has appeared in the literature [15][16][17][18][19], agar colony counts continue to be used extensively for the enumeration of microbes for estimation of survival [20][21][22][23], in stress studies [24][25][26], and perhaps most surprisingly in public health [27][28][29][30], even though alternative accurate techniques are available [31].…”

Thermal Inactivation Kinetics of Salmonella and Listeria in Ground Chicken Breast Meat and Liquid Medium

“…The heat resistance of pathogens in meat is influenced by meat species, muscle type, pH, fat content, and other environmental factors (Ghazala and others 1995;Veeramuthu and others 1998). Thermal resistances of some bacteria were higher in cooked meat broth than in conventional 0.05 M phosphate buffer at pH 7.0 (Bell and Delacy 1984). D-values ranging from 1.99 to 26.42 min were cited by Ghazala and others (1995) for Streptococcus faecium heated under pasteurization conditions in different heating media, such as brain-heart infusion broth, luncheon meat emulsion, ham broth, normal saline, nonfat milk, infant food, and buffalo milk.…”

THERMAL KINETICS of STREPTOCOCCUS FAECIUM IN NUTRIENT BROTH/SOUS VIDE PRODUCTS UNDER PASTEURIZATION CONDITIONS

“…Higher values than those in our study are perhaps due to the different strain, the more complex media (BHI), and the different plating agar. Other researchers obtained a Dm = 1.99 min for S. fuecium heated in BHI broth and plated on BHI agar, while the value increased to Dm = 4.00 min using luncheon meat emulsion as the heating medium (Bell and DeLacy 1984). Upon studying the thermal resistance of S. fuecium E-20 in ham broth using all purpose medium with Tween (APT) agar for plating, values obtained were: D, = 26.42, D, = 7.75, and D, = 3.42 min (Magnus et ul.…”

“…Since the presence and growth of S. faecium in sous vide foods may interfere with quality factors and possibly with safety, a heat resistance investigation of S. faecium in the present study was conducted in cooked ham broth. Furthermore, broth was used in this study because thermal resistance of S. faecium was higher in broth than conventional 0.05 M phosphate buffer of pH 7.0 (Bell and Delacy 1984), and also the broth resembles a food system more than a buffer system (Simpson et al 1994). A repair step incorporated into common isolation procedures would help detect injured yet viable cells.…”