Evaluation of 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate for Enumeration of Yeasts and Molds in Beverages

Introduction: Yeasts and molds are significant in the beverage industry; they can cause product spoilage and some species are pathogenic via the production of toxins. These organisms are important quality indicators, however the 5 - 7 days for traditional methods is a burden on the beverage industry. 3M™ Petrifilm™ Rapid Yeast and Mold (RYM) Count Plate were developed to address the need for rapid detection.

Purpose: The performance of Petrifilm RYM was evaluated by comparing yeast and mold counts in beverages with the USFDA BAM procedure. 

Methods: A total of eight beverage samples were analyzed; five naturally contaminated and three spiked with heat-treated Saccharomyces cerevisiae and Aspergillus niger spores. Three contamination levels were prepared; low (1-100 CFU/ml), medium (100-1,000 CFU/ml) and high (>1,000 CFU/ml). Two methods were used: Plate Count Agar pour-plate with 0.01% chloramphenicol incubated at 25 + 1°C for 5 - 7 days (USFDA BAM 2001); Petrifilm RYM incubated at 25 + 1°C and 28 + 1°C for 48 + 2 hours and 72 + 3 hours.

Results: Petrifilm RYM incubated at 25°C and 28°C for 48 h and 72 h, gave Pearson correlation coefficient scores (r) of 0.9986, 0.9990, 0.9996 and 0.9995, respectively. The accuracy profile was accomplished by setting the β-expectation tolerance intervals (β-ETI) at 80% and the acceptability limits (λ) at ± 0.3 and + 0.4 log units/ml. At 28°C, β-ETI limits were within λ = + 0.3 log units/ml. At 25°C, β-ETI limits fell outside λ = + 0.3 log units/ml but were within λ = + 0.4 log units/ml.

Significance: The 3M method correlated to the standard method at the incubation conditions of 25°C (48 h and 72 h) and 28°C (48 h and 72 h). Petrifilm RYM can detect yeast and mold in beverages within 48 - 72 hours whereas the standard method takes 5 - 7 days.