Enumeration of Fungi in Fruits by the Most Probable Number Method

Abstract

In this study, enumeration methods for fungi in foods were evaluated using fruits that are often contaminated by fungi in the field and rot because of fungal contaminants. As the test methods, we used the standard most probable number (MPN) method with liquid medium in test tubes, which is traditionally used as the enumeration method for bacteria, and the plate-MPN method with agar plate media, in addition to the surface plating method as the traditional enumeration method for fungi. We tested 27 samples of 9 commercial domestic fruits using their surface skin. The results indicated that the standard MPN method showed slow recovery of fungi in test tubes and lower counts than the surface plating method and the plate-MPN method in almost all samples. The fungal count on the 4th d of incubation was approximately the same as on the 10th d by the surface plating method or the plate-MPN method, indicating no significant differences between the fungal counts by these 2 methods. This result indicated that the plate-MPN method had a number agreement with the traditional enumeration method. Moreover, the plate-MPN method has a little laborious without counting colonies, because fungal counts are estimated based on the number of plates with growing colonies. These advantages demonstrated that the plate-MPN method is a comparatively superior and rapid method for enumeration of fungi.

Influence of Airflow on Laboratory Storage of High Moisture Corn Stover

“…Water extracts were prepared by creating a 1:10 ratio of wet biomass (50 g) to BupH phosphate buffered saline (Thermo Scientific, Rockford, IL) and shaking at 200 rpm for 3 h at room temperature. Fungal plate MPNs were performed based on the method by Watanabe et al [25] using potato dextrose agar with 100 mg/L chloramphenicol and were incubated at room temperature for 10 days. All MPNs were performed with dilutions from 10 −2 to 10 −7 in Fig.…”