COMPARISON OF MACERATION AND ENUMERATION PROCEDURES FOR AEROBIC COUNT IN SELECTED SEAFOODS BY STANDARD METHOD, PETRIFILM(TM), REDIGEL(TM), AND ISOGRID

The first objective of the study was to compare two methods of macerating samples: manual shaking versus homogenizing in a Waring blender. The two methods were applied to 12 replicates of raw clams, raw cod, cooked lobster, and cooked shrimp. The second objective was to compare three commercial methods - Isogrid, Redigel(TM), and Petrifilm(TM) - with the standard aerobic plate count method. For this, raw cod, raw mussels, and frozen cooked shrimp were used as test material. The manual shaking method was highly correlated (r = 0.98) with the blender homogenization method. Compared with conventional blender homogenization, the manual shaking technique gave recoveries of 98.2% for clams, 99.7% for cod, 101.6% for lobster, and 97.2% for shrimp. No significant differences were found between the four enumeration methods applied to cod, mussels, and shrimp; F = 0.25; P = 0.86, respectively. Correlation coefficients obtained by plotting log10 CFU/g for one enumeration method against a second method ranged from 0.86 to 0.99. Counts obtained with the three commercial methods were from 97.6 to 104.0% of the counts obtained by the standard method. These results suggest that for fish products, die Isogrid, Redigel(TM), and Petrifilm(TM) methods are suitable alternatives to the conventional standard plate count method.