Thermal resistances and lactate and diacetate sensitivities of bacteria causing bologna discolouration

This report describes the effects of heat, sodium lactate, and sodium diacetate on the viabilities of Weissella viridescens ATCC 12706, Aerococcus viridans MPL-1 and MPL-B, and Carnobacterium viridans ATCC BAA 336. The latter three organisms were isolated from commercial product and have previously been shown to produce green discolourations in cooked cured bologna. W. viridescens was heat resistant in beef bologna (D60 °C=14.7 min) but not in APT broth. A. viridans and C. viridans were much more sensitive to heat (D60 °C in beef bologna ≤1.3 min), indicating that these organisms were probably post-pasteurization contaminants. Sodium lactate (3.0%) alone or in combination with 0.3% sodium diacetate slowed the growth rate and reduced the final cell numbers of A. viridans and C. viridans in inoculated bologna. W. viridescens was only slightly affected by the combined antimicrobials. The combination of sodium lactate and sodium diacetate prevented A. viridans and C. viridans from affecting the colour of beef bologna. However, lactate and diacetate themselves reduced red colour, as measured by HunterLab colourimetry. HunterLab a values for fresh beef bologna were 13.4 (no antimicrobial added), 9.6 (3.0% sodium lactate), 8.0 (0.3% sodium diacetate), and 7.9 (3.0% sodium lactate+0.3% sodium diacetate).