Purpose: The objectives of this study were to validate this PCR-based test method in plant extracts to detect yeast and mold at as low as 25 CFU/g and to compare the effectiveness of sample processing through different preparation procedures against growth/PCR inhibition issues coming from the complexity of food matrices.
Methods: Twenty naturally contaminated plant extracts were tested by the test method and China GB reference method. For the test method, samples were incubated at 25°C for 44 - 52hrs, followed by lysis and PCR processes according to the test kit User Guide. To avoid growth/PCR inhibition from the samples, various incubation time, different pooled sample procedures and lysate dilutions were investigated.
Results: For the twenty tested samples, the preferred sample processing was worked out for the test method, which gave identical results to the reference method. Chi-square analysis indicates the test method and the reference method returned statistically equivalent results.
Significance: The results demonstrate this PCR-based assay can be used to reliably and accurately detect yeast and mold in plant extracts at low levels to meet manufacturers’ product specifications. Furthermore, the faster time to result allows the analysis lead time for Quality Control procedures to be reduced to 2 days, compared to 5 days required with the reference method, resulting in faster release of product, reductions in inventory and gains in working capital.