Is Your Grind Size the Right Size? Grain Preparation for Mycotoxin Testing

Author: Alex Kostin, Applications Scientist

Mycotoxins are toxic fungal metabolites produced by molds such as Aspergillus and Fusarium. They are commonly found in grains, nuts, coffee, spices, and other agricultural commodities when soil, weather, and storage conditions favor mold growth. Mycotoxins including aflatoxin, deoxynivalenol (DON), fumonisin, ochratoxin, and zearalenone pose serious health risks to both humans and animals. They can be carcinogenic and cause damage to the liver, kidneys, immune system, and nervous system.

Lack of testing or inaccurate test results can lead to product loss, costly recalls, or even legal consequences. For these reasons, accurate mycotoxin testing is essential in agricultural products and feed formulations.

Sample Preparation Challenges

To perform mycotoxin testing with either lateral flow, ELISA, or chromatographic reference methods, everyone starts at the same place - a sample is collected from a truckload or incoming lot of material. However, pulling a representative sample for test preparation can be challenging. One very important step in the process that can get overlooked is the grind size or particle size of your sample.

Grind size and uniformity can dramatically impact the accuracy, repeatability, and reliability of your mycotoxin test results. Because mycotoxins are not evenly distributed in a batch, a few contaminated kernels could cause one sample to exceed limits while another appears clean. This makes sampling and grinding very difficult but very important to get a true representation of the batch.

Recommendations for Effective Grind Size

Grinding improves sample homogeneity, but the particle size matters. If the grind is too coarse, there is a risk of pockets of contamination that don't get evenly distributed and could lead to over or under reporting.

Studies done by Trilogy® Analytical Laboratory have shown that the finer the particle size of a sample, the tighter the distribution of results and less variability observed. When comparing a grind size:

• 10-mesh sieve (2,000 microns, 50% pass-through): variability between 20-50% across mycotoxins.
• 20-mesh sieve (850 microns, 50% pass-through): improved consistency.
• 20-mesh sieve (95% pass-through): variability reduced to <10%.

Based on these findings, USDA GIPSA guidelines recommend that 95% of the ground sample pass through a 20-mesh sieve. This grind size minimizes variability and can be achieved using mills such as the Sasso Mill or Bunn® grinder.

Following Regulations Leads to Success

In regulated industries, incorrect grind size and results can lead to non-compliance with official methods. This means your results might not be accepted by regulatory agencies or trading partners. Mycotoxin testing is all about accuracy and confidence in the sample and the test method. Grind size plays a big role in achieving this. By following the correct particle size guidelines outlined by standards organization such as AOAC and regulatory bodies like USDA FGIS using the proper grinding equipment, and routinely verifying the grind, customers can help ensure that test results are accurate and reflective of the product's quality and compliance.

Reduce Sample Variability with Neogen®

Our Sasso Mill is an innovative commercial grade grain grinder (with FGIS approval) meeting industry needs for effective grind size and consistent sample preparation for mycotoxin testing. It has been designed to advance the efficiency of your workflow and consistency of your test results. Reach out to our team to learn more!

Need mycotoxin test kits? Learn more about our Reveal® lateral flow devices (LFD) and Veratox® enzyme-linked immunosorbent assay (ELISA) test kits here. With over 45 years in mycotoxin testing, Neogen is dedicated to providing industry-leading technology with hands-on technical support to meet your needs.

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References:

• USDA FGIS Mycotoxin Handbook, January 2023
• Aubert, Wong. 2024. Monitoring and Verification Technologies of Support Preventative Control Programs- Feed Regulations
• Maune C., Maune C. 2021. The Effect of Grind and Extraction Size on Aflatoxin Result Variability.
• Brunkhorst V., Maune C. 2021. The Effect of Grind and Extraction Size on Dexoynivalenol Result Variability.
• Maune C., Maune T. 2021. The Effect of Grind and Extraction Size on Fumonisin Result Variability.
• Brunkhorst V., Maune C. 2021. The Effect of Grind and Extraction Size on Zearalenone Result Variability.

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