EVALUATION OF BIFIDOBACTERIA FOR THE PRODUCTION OF ANTIMICROBIAL COMPOUNDS AND ASSESSMENT OF PERFORMANCE IN COTTAGE CHEESE AT REFRIGERATIONTEMPERATURE

Twelve strains of bifidobacteria were identified which exhibited a bro ad spectrum of antagonistic activity against both Gram-positive and Gr am-negative indicators, especially Pseudomonas species, using deferred antagonism spot plate assays. Inhibitory action was shown to be unrel ated to hydrogen peroxide production and not solely dependent on acidi ty. However, attempts to detect inhibitory activity in cell-free super natant fluids from these strains were unsuccessful. The production of inhibitory compound(s) by Bifidobacterium infantis NCFB 2255 was shown tn be an unstable trait resulting in phenotypic alternation between p roduction and non-production. Results from food trials using commercia l cottage cheese which was inoculated with the inhibitor-producing str ains of Bif. infantis NCFB 2255 and Bif: breve NCFB 2258 indicated tha t levels of Pseudomonas were reduced, but this observation was species -dependent. The viability of bifidobacteria themselves during storage in cottage cheese at refrigeration temperature was found to be a strai n variable trait.