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Direct plating versus dilution plating in qualitatively determining the mold flora of dried beans and soybeans
Abstract:
Two methods presently used for examining whole foods and feeds for viable molds were evaluated for their relative effectiveness in the qualitative determination of the total number of mold species present in soybeans and dried beans: the direct plating method and the serial dilution method. Sixty-nine soybean samples and 40 dried bean samples were examined. Although the quantitative results of this study were inconclusive, the qualitative results show that the direct plating method was substantially more effective in detecting individual mold species. An average of 12.9 and 10.9 species was detected by the direct plating method in whole soybean and dried bean samples, respectively. An average of 4.4 and 2.8 species was detected by the dilution method in ground soybean and dried bean samples, respectively. A total of at least 37 mold species were found in the study, including 10 toxicogenic species. With few exceptions, detection rates of the 37 individual species were substantially greater among the samples examined by direct plating than those examined by serial dilution.
Insights
The direct plating method is superior for detecting mold species in soybeans and dried beans compared to serial dilution. This method identified significantly more mold species, including toxicogenic ones, in food and feed samples.
Area of Science:
- Food microbiology
- Mycology
- Agricultural science
Background:
- Molds in food and feed pose risks, including potential toxicity.
- Accurate detection of mold species is crucial for food safety and quality assessment.
- Current methods for mold enumeration in agricultural commodities require evaluation.
Purpose of the Study:
- To compare the effectiveness of direct plating and serial dilution methods for qualitative mold detection.
- To determine the relative ability of each method to identify diverse mold species in soybeans and dried beans.
- To assess the detection rates of specific mold species, including toxicogenic ones.
Main Methods:
- Evaluation of two methods: direct plating and serial dilution.
- Analysis of 69 soybean and 40 dried bean samples.
- Qualitative assessment of mold species diversity and detection rates.
Main Results:
- Direct plating detected significantly more mold species per sample (average 12.9 in soybeans, 10.9 in dried beans) than serial dilution (average 4.4 in soybeans, 2.8 in dried beans).
- Overall, at least 37 mold species were identified, with 10 being toxicogenic.
- Detection rates for individual species were consistently higher with the direct plating method.
Conclusions:
- The direct plating method is substantially more effective for the qualitative determination of mold species in soybeans and dried beans.
- This method offers improved detection of fungal diversity, including potentially harmful species.
- Findings support the use of direct plating for comprehensive mold analysis in agricultural commodities.