Comparison of Maceration and Enumeration Procedures for Aerobic Count in Selected Seafoods by Standard Method, Petrifilm™, Redigel™, and Isogrid

Abstract

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™, and Petrifilm™ - 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, the Isogrid, Redigel™, and Petrifilm™ methods are suitable alternatives to the conventional standard plate count method.