👤 Mark Mozola

Soleris® Direct Yeast and Mold (DYM) is a growth-based, automated method for detection of yeast and mold in select foods and other sample types including nutraceuticals and cosmetics. The Soleris method is used in a "dilute-to-specification" or threshold manner in which a result is scored as positive or negative around a predetermined cutoff (in CFU/g) established by the dilution and volume of sample homogenate tested. The objective of this study was to validate the method for testing of dried cannabis flower. The validation was conducted under the Emergency Response Validation program of the AOAC Research Institute. The study included inclusivity and exclusivity testing, in particular testing of yeast and mold species associated with cannabis, and a matrix study in which Soleris method presumptive results were compared with Soleris confirmed results using Dichloran Rose-Bengal Chloramphenicol (DRBC) agar for confirmation. Samples at four different levels of natural yeast and mold contamination were tested at two test thresholds. In inclusivity testing, all 63 yeast and mold strains tested produced positive results within the specified test duration of 72 h. In exclusivity testing, 36 of 37 strains tested produced no detection within 72 h. In matrix testing, there were no significant differences between Soleris presumptive and confirmed results for any contamination level or test threshold as determined by probability of detection analysis. Results indicate that the Soleris method is an effective procedure for detection of yeast and mold in dried cannabis flower. With the Soleris method, results are available within 72 h compared with the 5-7 days required for microbiological culture methods. Show less

Here we describe results of a study to validate minor reagent formulation changes to the Soleris Direct Yeast and Mold (DYM) automated growth-based method for semi-quantitative detection of yeast and mold in food products. In order to reduce the maximum concentration of the selective agent chloramphenicol in the Soleris reagents, chloramphenicol was removed from the selective supplement and added to the vial growth medium itself. Therefore, both the vial medium and supplement have been reformulated in an alternative version of the method. A probability of detection (POD) statistical model was used to compare Soleris results at multiple test thresholds (dilutions) with plate counts determined using the U.S. Food and Drug Administration Bacteriological Analytical Manual dilution plating procedure. Three matrixes were tested; yogurt, tomato juice, and cocoa powder. POD analysis showed that the percentage of positive Soleris tests at various test thresholds were within the limits predicted by the reference method plate counts for all matrixes evaluated. Real-time stability data on three manufactured lots showed that the modified Soleris vial and supplement are stable for at a minimum of 10 months when stored at 2-8°C. In sum, results presented here demonstrate that the modifications to the Soleris DYM vial and supplement do not impact method performance. The modified Soleris DYM method can be used as an accurate alternative to conventional dilution plating procedures for semi-quantitative determination of yeast and mold at threshold levels, while saving as much as 3 days in analysis time. Show less

A study was carried out to determine the efficacy of the Soleris Direct Yeast and Mold (DYM) automated growth-based method for semiquantitative detection of yeast and mold in a variety of food products. A probability of detection (POD) statistical model was used to compare Soleris results at multiple test thresholds (dilutions) with plate counts determined using the U.S. Food and Drug Administration Bacteriological Analytical Manual, Chapter 18, dilution plating procedure. Fourteen naturally contaminated food products were tested, with Soleris testing performed at three or more threshold levels for each food. Using the POD model, the majority of Soleris test results were in statistical agreement with the reference plating procedures. The exceptions included a single threshold level in yogurt, black pepper, dried fruit, and dry pet food, and two levels in nonfat dry milk and saw palmetto powder. In all but one of these instances, the exception being pet food, the statistical disagreement was due to Soleris estimating a higher level of contamination than the reference method. Results of ruggedness testing showed that the Soleris method produced accurate results even when significant variances in a critical operating parameter, incubation temperature, were introduced. Results of the internal and independent laboratory validation studies showed that the Soleris DYM method can be used as an accurate alternative to conventional dilution plating procedures for evaluation of yeast and mold counts at threshold levels, while saving as much as 72 h in analysis time. Show less