Technical profile: sampling secrets
August 01, 1997
by Teresa Acklin
Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was written by Fred Norwood, vice-president of marketing, Cereal Ingredients Laboratory Services, Kansas City, Missouri, U.S.
Testing laboratories provide a valuable service to milling operations by determining and documenting the quality of the grain you take in and the finished product you put out. To ensure the accuracy of your laboratory results, however, it's important to make sure grain or finished product samples are taken correctly.
The U.S. Federal Grain Inspection Service offers guidelines for proper collection of grain. However, these guidelines also are useful for sampling flour or other finished products.
Representative samples may be drawn from truck lots, car lots and barge lots either by probe, pelican, Ellis cup, woodside sampler or diverter-type mechanical sampler. The F.G.I.S. requires that samples from export cargoes, ship lots or barge lots be collected by a diverter-type sampler.
Sample sizes should be about 2.4 liters but not less than 1.9 liters. They should be handled securely, protected from manipulations, substitution or careless handling.
Regulations aside, there are a number of steps you can take to help your testing laboratory do a thorough and accurate job with your samples.
Always send enough sample to run the analysis two or three times. This allows for rechecks of the sample in case of a dispute between buyer and seller.
When you send your samples out, always mark sample numbers clearly on the outside of each sample bag. This is especially critical with rail cars, since these usually involve a large number of samples from a large number of cars.
Never reuse sample bags as contamination may occur from one sample to another. While this is most important when testing for mycotoxins, the rule applies to all samples.
Never clean a sample prior to bagging, or it will not be representative of the storage unit, whether it's a rail car, bin, barge or ship hold. This is especially important when testing for mycotoxins because the highest levels of contamination often are found in foreign materials rather than in the product.
When sending large bagged samples of 23 kilograms or more, double-bag the product to protect it from contamination from puncture or tearing during transit.
Most laboratories store samples for only 30 days. If you need to retain samples for longer periods, in the case of export shipments or long deliveries, let the lab know in advance.
Always retain another sample of the product in-house in case the original sample is lost during shipment to the testing laboratory.