Technical note: Enumeration of mesophilic aerobes in milk: Evaluation of standard official protocols and Petrifilm aerobic count plates

Dispersion of mesophilic aerobes counts in raw and pasteurised milk obtained by conventional (x-axis) and Petrifilm Aerobic Count (y-axis; Petrifilm, 3M, St. Paul, MN) plating and incubated at 3 distinct conditions [30°C for 72h (ISO, 2003); 32°C for 48h (American Public Health Association; Wehr and Frank, 2004); and 36°C for 48h (Brasil, 2003)]. In each graphic: y=ax + b [correlation formula, indicating slope (a) and intercept (b); correlation index ®, determination coefficient (r²); number of repetitions (n); mean variance (mv); and level of significance (P).