Evaluation of the petrifilm dry rehydratable film for the enumeration of yeasts and moulds in naturally contaminated foods

• Published in: Journal of food safety Vol. 30; no. 2; pp. 506 - 514
• Main Authors: Tournas, V. H, Feliciano, L, Katsoundas, E. J
• Format: Journal Article
• Language: English
• Published: Malden, USA Malden, USA : Blackwell Publishing Inc 01.05.2010; Blackwell Publishing Inc; Wiley; Blackwell Publishers Inc
• Subjects: Biological and medical sciences; dairy products; dried fruit; films (materials); food contamination; Food contamination & poisoning; food grains; Food industries; food pathogens; Food safety; fresh-cut foods; fruit juices; Fundamental and applied biological sciences. Psychology; Fungi; General aspects; grain products; Hygiene and safety; linear models; microbial colonization; microbial contamination; microbial detection; microbial growth; molds (fungi); nuts; produce; Regression analysis; Testing; Yeast; yeasts; Evaluation; Yeast; Microbiological testing; Film; Alteration; Mould; Food; Enumeration(counting)
• ISSN: 0149-6085; 1745-4565
• DOI: 10.1111/j.1745-4565.2010.00223.x

Two hundred thirty-seven samples from six food groups (tree nuts, grains and grain products, dried fruits, fresh produce, fruit juice and dairy products) were tested for levels of fungal contamination using the Petrifilm dry rehydratable film for yeast and mould (PYM ) enumeration (3M Microbiology, St. Paul, MN) and the Food and Drug Administration (FDA) official method. Results indicated that PYM performed very well for all tested commodities giving YM counts similar to those of the FDA method. Statistical analysis of the data (t-test) revealed no significant differences between the two methods for all foods tested. Linear regression analysis showed that the correlation coefficients between the two methods were over 0.90 for 91% of the commodities tested. Some difficulties were encountered during counting of the colonies on PYM as yeast colonies on this medium tend to be very small with rather faded colorations. Assessment of the efficacy of Petrifilm and determining its equivalence to traditional, validated methods will give the testing laboratories and the industry an alternate option for the enumeration of fungi in foods. The use of Petrifilm would be especially useful when analyst time is limited as it requires no media preparation and minimal time for sample inoculation.