In 2008, Health Canada announced it was considering the establishment of maximum levels for ochratoxin A (OTA) in unprocessed wheat, oats, and their products. The Canada Grains Council and Canadian National Millers Association initiated two studies to measure the variability and distribution among sample test results for unprocessed wheat and oats so that scientifically based OTA sampling plans could be designed to meet regulatory and industry requirements. Sampling statistics related to detecting OTA in oats has been published. 54 OTA contaminated wheat lots representing three wheat classes were identified for the sampling study. Each lot was sampled according to a nested experimental protocol where sixteen 2-kg laboratory samples were taken from each lot, multiple 5-g test portions were taken from each comminuted 2-kg laboratory sample, and multiple OTA measurements were made on each test portion using liquid chromatography. The sampling, sample preparation, and analytical variances associated with each step of the OTA test procedure were found to be a function of OTA concentration and regression equations were developed to predict the functional relationships between variance and OTA concentration. When sampling a wheat lot containing 5 µg/kg OTA with an OTA test procedure consisting of a sampling step employing a single 2-kg laboratory sample, sample preparation step employing a single 100-g test portion, and an analytical step that used liquid chromatography to quantify OTA, the sampling step accounted for 95.3% of the total variability. The observed OTA distribution among the 16 OTA sample results was found to be positively skewed and the negative binomial distribution was selected to model the OTA distribution among sample test results. The sampling statistics were incorporated into the FAO Mycotoxin Sampling Tool and the chances of rejecting good lots and accepting bad lots were calculated for various sampling plan designs.
RESEARCH ARTICLE
Variability and distribution among sample test results when sampling unprocessed wheat lots for ochratoxin A
T.B. Whitaker Related information
1Biological and Agricultural Engineering Department, North Carolina State University, Weaver Laboratories, P.O. Box 7625, Raleigh, NC 27695-7625, USA
*whitaker@ncsu. edu
, A.B. Slate Related information*whitaker@ncsu.
1Biological and Agricultural Engineering Department, North Carolina State University, Weaver Laboratories, P.O. Box 7625, Raleigh, NC 27695-7625, USA
, T.W. Nowicki Related information2Consultant to Canada Grains Council, 220 Portage Avenue, Winnipeg, MB R3C 0A5, Canada
, F.G. Giesbrecht Related information3Department of Statistics, North Carolina State University, SAS Hall, P.O. Box 8203, Raleigh, NC 27695-8203, USA
†deceased
†deceased
World Mycotoxin Journal: 9
(2)- Pages: 163 - 178
Published Online: December 21, 2015
Abstract
Keywords: sampling plan, maximum level, buyer’s risk, seller’s risk, OC curve
2023 Journal Impact Factor
2.0
source: Journal Impact Factor 2023™ from Clarivate™
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