Abstract
Azide esculin agar plate method (AE agar, 1% polypeptone, 0.5% yeast extract, 0.5% NaCl, 0.4% K2HPO4, 0.15% KH2PO4, 0.05% NaN3, 0.1% esculin, 0.05% ferric ammonium citrate, 1.5% agar, pH 8.0) for enterococcus test of frozen foods was developed in this work.
Among 221 enterococcus strains including 179 strains freshly isolated from feces, polluted water and frozen foods, and 42 stock strains 217 (98.2%) strains formed typical colonies surrounded by black halos on AE agar plates after 24hr incubation at 45°C. On the other hand, 234 (96.3%) of 243 typical colonies produced in AE agar test of 26 frozen food samples were identified with enterococci by completed test. Using AE agar plate method and Most Probable Number (MPN) method of AC-AC (Azide Citrate) broth procedure, enterococcus counts of 50 frozen food samples were determined. It was shown that although enterococcus counts obtained by both methods were comparable, AE agar plate method was preferable to the MPN method because of the simplicity and rapidity of the test procedures.
AE agar plate test followed by AC broth confirmation test may successfully be used for a rapid determination of enterococci in frozen foods.
