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United States Department of Agriculture

Agricultural Research Service

Title: Sample Comminution for Mycotoxin Analysis: Dry Milling Or Slurry Mixing?

Authors
item Spanjer, M - FOOD & CONSUMER SAFETY
item Scholten, J - FOOD & CONSUMER SAFETY
item Kastrup, S - WIERTZ, EGGERT & JORISSEN
item Jorissen, U - WIERTZ, EGGERT & JORISSEN
item Schatzki, Thomas
item Toyofuku, Natsuko

Submitted to: Journal of Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2005
Publication Date: January 1, 2006
Citation: Spanjer, M.C., Scholten, J.M., Kastrup, S., Jorissen, U., Schatzki, T.F., Toyofuku, N. 2006. Sample comminution for mycotoxin analysis: dry milling or slurry mixing?. Journal of Food Additives & Contaminants. 23(1):73-83.

Interpretive Summary: A comparison was made between dry milling (grinding samples in a large blender without liquids which results in a powder) and slurry mixing (blending samples in a blender with liquid which results in a thick liquid). Both of these methods are used to prepare samples for mycotoxin (a carcinogenic material found in granular foodstuffs like pistachios) analysis. Cacao, green coffee, almonds and pistachio samples of 10 kg were dry milled by a Romer Analytical Sampling mill and all three samples were analyzed for aflatoxin B1 or ochratoxin A content. The samples were tested on how well the milling process homogenized the sample and the distribution of particle sizes produced by the dry milling process. The results from the dry milling were more variable than for slurry mixing. This difference was explained on the basis of measured particle size distributions for both milling types. Measurements also showed slight differences in mycotoxin content of samples on the basis of milling procedures. This might lead to food products being wrongly accepted or rejected on the basis of an erroneous sampling result. It was concluded that sample preparation was best performed by slurry mixing which produced smaller particles and, consequently, more homogeneous samples with lowest variation. Additional data are given on analytical results in 10 kg subsamples taken from the 30 kg samples as described in Commission Directive 98/53/EC.

Technical Abstract: A comparison was made between dry milling and slurry mixing as a comminuting step preceding mycotoxin analysis. Sample schemes of up to 30 kg are mandated by EC legislation. Cacao, green coffee, almonds and pistachio samples of 10 kg were milled by a Romer Analytical Sampling mill and all three samples were analyzed for aflatoxin B1 or ochratoxin A content. The homogenization process was evaluated in view of the analytical results, coefficients of variation for different mills and particle size distributions. CV values for the comminuting step were higher for dry milling then for slurry mixing. This difference was explained on the basis of measured particle size distributions for both milling types. Measurements also showed slight differences in mycotoxin content of samples on the basis of milling procedures. This might lead to lots being wrongly accepted or rejected on the basis of an erroneous subsample result. It was concluded that sample comminution was best performed by slurry mixing which produced smaller particles and, consequently, homogeneous samples with lowest CV. Additional data are given on analytical results in 10 kg subsamples that originate from the aggregate 30 kg sample as described in Commission Directive 98/53/EC.

Last Modified: 9/20/2014