COMPARISON OF THE SIMPLATE(TM) TOTAL PLATE-COUNT METHOD WITH PETRIFILM(TM), REDIGEL(TM), AND CONVENTIONAL POUR-PLATE METHODS FOR ENUMERATING AEROBIC MICROORGANISMS IN FOODS

The SimPlate(TM) Total Plate Count (TPC) method, developed by IDEXX La boratories, Inc., is designed to determine the mast probable number of aerobic microorganisms in foods. The 24-h test was compared to the co nventional plate count agar (PCA) method, the Petrifilm(TM) Aerobic Co unt plates, and the Redigel(TM) Total Count procedure for enumerating microflora in 751 food samples. Results using the SimPlate(TM) TPC met hod were highly correlated (r greater than or equal to 0.96) with resu lts from other test methods. Slopes (0.96-0.97) were not significantly different from 1, and) y intercepts (-0.03-0.08) were not different f rom 0. The SimPlate(TM) has a high counting range (>1600 most probable number per single dilution), thus requiring fewer dilutions of sample s compared to other methods evaluated. Some foods, e.g., raw liver, wh eat flour, and nuts, contain enzymes that gave false-positive reaction s on SimPlates(TM). Overall, however, the SimPlate(TM) TPC method is a suitable alternative to conventional PCA, Petrifilm(TM), and Redigel( TM) methods for estimating populations of mesophilic aerobic microorga nisms in a wide range of foods.