E. Mycotoxin Testing
Detection of mycotoxins in sorghum is complex. The fungi producing the mycotoxins often do not grow uniformly in a field or across a geographic area. As a result, the detection of any mycotoxin in sorghum, if present, is highly dependent upon the concentration and distribution of the mycotoxin among kernels in a lot of sorghum, whether a truck load, a storage bin, or a railcar.
The objective of the testing for the 2015/2016 Harvest Survey is only to report the frequency of occurrences of the mycotoxin in the current crop, but not specifc levels of the mycotoxin in sorghum exports. To report the frequency of occurrences of aflatoxins and DON for the harvest samples, AGE performed the mycotoxin testing using FGIS protocol and approved test kits. FGIS’s protocol requires a minimum of a 908-gram (2-pound) sample from trucks to grind for aflatoxin testing and approximately a 200-gram sample to grind for DON testing. For this study, a 1000-gram laboratory sample was subdivided from the 2.5-kg survey sample for the mycotoxin analysis. The 1-kg survey sample was ground in a GIPSA-FGIS-approved Romer Model 2A mill so that 60-75% would pass a 20-mesh screen. From this well-mixed ground material, a 50-gram test portion was removed for each mycotoxin tested. ROSA AFQ-FAST and DONQ-FAST5 quantitative test kits were used for the aflatoxin and DON analysis, respectively. The DON was extracted with water (5:1), while the aflatoxins were extracted with 70% methanol and 30% distilled water. The extracts were tested using the ROSA lateral flow strips, and the mycotoxins were quantified by the Charm EZ-M system.
The ROSA quantitative test kits report specifc concentration levels of the mycotoxin if the concentration level exceeds a specifc level called a “Limit of Detection” (LOD). The LOD is defined as the lowest concentration level that can be measured with an analytical method that is statistically different from measuring an analytical blank (absence of a mycotoxin). The LOD will vary among different analytical methods developed for different types of mycotoxins and commodity combinations. The LODs for the ROSA AFQ-FAST and DONQ-FAST5 are 2.0 parts per billion (ppb) aflatoxins for diluted extract, and 0.1 parts per million (ppm) DON for diluted extract.
A letter of performance has been issued by FGIS for the quantification of aflatoxins and DON using the ROSA AFQ-FAST and DONQ-FAST5 kits, respectively.
The mycotoxin tests performed by AGE for the 2015/2016 Export Cargo Survey were conducted using the same methods as the 2015/2016 Harvest Survey. The 47 samples for which aflatoxin testing was performed at the FGIS field offces were tested in accordance with FGIS offcial procedures. A sample of at least 10 pounds of sorghum was used according to FGIS offcial procedures. The 10-pound sample was ground using a FGIS-approved grinder. Following the grinding stage, two 500-gram ground portions are removed from the 10-pound comminuted sample using a riffle divider. From one of the 500-gram ground portions, a 50-gram test portion is randomly selected for testing. After adding the proper extraction solvent to the 50-gram test portion, aflatoxin is quantified. The following FGIS-approved quantitative test kits may have been used: VICAM AflaTest™, Romer Labs FluoroQuant Afla or FluoroQuant Afla IAC, Envirologix QuickTox™ for QuickScan Aflatoxin (AQ 109 BG and AQ 209 BG), Neogen Reveal Q+ for Aflatoxin or Veratox® Aflatoxin Quantitative Test, Charm Sciences ROSA® FAST or WET-S5™ Aflatoxin Quantitative Tests, or R-Biopharm RIDASCREEN® FAST Aflatoxin SC test or RIDA QUICK Aflatoxin RQS.