Optional Quality Assessment Services 

USDA Grain Inspection, Packers and Stockyards Administration
STOP 3601, 1400 Independence Ave., SW,  Washington, D.C. 20250-3601

USDA 22jan01

[About the USDA GIPSA]

Corn Oil, Protein and Starch

For several years, producers of specialty varieties of corn grown for a particular end-use expressed an interest and need to analyze corn for oil, protein and starch. A 1996/97 quality report estimated that approximately 3.2 to 3.8 percent of the U.S. harvested acreage were specialty varieties.

Future crop production estimates identified High-Oil Corn (HOC) as the fastest growing specialty corn in the United States. By the year 2000, production of HOC is expected to reach 3 million acres and represent a significant part of the specialty varieties produced and traded in the marketplace. HOC is used primarily by livestock feeders to replace animal fat previously added to livestock rations and to help animals gain weight more rapidly.

Due to the anticipated increase in specialty corn production and market demand for reliable official testing procedures, GIPSA offers protein, oil, and starch testing as an official testing service. This lets GIPSA provide the corn industry with accurate results that the industry can rely on to negotiate price while providing the best information possible to determine end-product yield.

The testing service is provided by GIPSA and official agencies equipped with standardized NIRT instruments. The NIRT calibrations were developed to automatically provide protein, oil, and starch percentages on a dry matter basis.

Ethylene Dibromide Testing

Ethylene dibromide (EDB) is a fumigant used to kill insects.  Fumigants are used because once insects are inside a grain mass, only fumigation can reach the infestation. The objective of fumigation is to permeate the grain mass with the gas at high enough levels for a sufficient length of time to kill all stages of insects present.  Food safety is the primary reason for testing grain for fumigant residues (fumigants are very toxic). Ethylene dibromide ingested can cause gastroenteritis, liver necrosis, and renal tubular damage.

GIPSA tests for EDB residues on wheat, corn, and soybeans - by request on a fee basis.  To conduct EDB testing, a sample is ground in a sealed blender with sodium sulfate. After grinding, the "head space" above the mixture is sampled and injected onto a gas chromatograph with an ECD detector.  Results are reported as either < or > 10 ppb (pass/fail type test).  It generally takes 12 business hours from sample receipt to receive test results.  Due to the nature of the test, it is run only at the Technical Services Division.

Falling Number Determinations

Shortly before sprouting can be seen, there is a dramatic increase in the alpha-amylase enzyme activity of wheat kernels. Millers and bakers are very concerned about the level of alpha-amylase activity in wheat flour because excessive amounts break down starches to the extent that the flour's baking properties are adversely affected.

The Falling Number (FN) determination indirectly measures alpha-amylase activity in a manner that simulates some of the changes flour undergoes during baking. Specifically, the "falling number" is the number of seconds required to stir and allow the stirrer to fall a measured distance through a hot aqueous flour gel undergoing liquefaction. A high falling number indicates low alpha-amylase activity whereas a low falling number indicates high alpha-amylase activity. There is very little alpha-amylase activity in samples with a FN result above 400.

The FN test is requires two 7-gram representative portions taken from 250-grams of a wheat sample after grinding. All FN determinations are performed in duplicate and the average of the duplicate test results are reported on the official certificate. FN results are reported on a 14 percent moisture basis unless the applicant specifies another basis. Retest and appeal services are available.

GIPSA offers Falling Number determinations for both wheat (grain) and all wheat flours (commodities). For grain samples, testing services are available at selected GIPSA field offices, official state agencies, and the Technical Services Division. However, testing of commodity samples (wheat flours) is only available at the Technical Services Division. For both grain and commodities, the maximum sample turnaround time is 2 working days.

To request service, contact your nearest GIPSA field office or the Technical Services Division.

Heavy Metal Analysis

The presence of heavy metals in grains is a concern for many countries importing grains. In response to this concern, GIPSA developed an analytical procedure to analyze corn and wheat for lead and cadmium. The procedure involves microwave digestion of the sample and quantitation using atomic absorption spectroscopy. The analysis is an optional service available from GIPSA's Technical Services Division.

Mycotoxin Analyses

Mycotoxins are toxic substances produced by a wide variety of fungi (molds). GIPSA has been asked by farmers, grain dealers, and foreign buyers to quantitatively measure aflatoxin, vomitoxin, zearalenone, and fumonisin. GIPSA currently measures aflatoxin and vomitoxin using commercial mycotoxin test kits that are of relatively low cost, rapid, and accurate. Results are available using the reference method at the Board appeal level. The accuracy of the test kits is monitored by a reference method involving complex  instrumentation and lengthy test procedures. Future activities will include the development of reference methods for fumonisin and zearalenone, and the evaluation of commercially available test kits for these two mycotoxins.

Pesticide Residue Analysis Service

The U.S. food supply is one of the safest in the world.  However, to address public concerns about the effects of agricultural pesticides on human health and environmental quality, GIPSA offers optional screening on corn (including popcorn), wheat, soybeans, and barley.  GIPSA screens samples for multiple compounds (specific pesticides for each grain are listed in Directive 918.4). 

A unique aspect of GIPSA's pesticide residue testing service is that, for one fee, a sample is screened for compounds in all three classes of pesticides (organo-nitrogen, organo-chlorine, and organo-phosphates).  Most of the common pesticides in each of these classes are included in our screen.  The compounds included in GIPSA's screening list were selected based on the commonly used pesticides for that grain, concentrating on insecticides.  The Agricultural Chemical Usage report was used as a basis for determining commonly used pesticides.  All compounds are screened using gas chromatography/mass spectrometry.

Results are provided within 2 working days of laboratory receipt of the sample.  (Weekend analysis services are available upon request.)

For more information on pesticides tested or obtaining service, please see FGIS Program
Directive 9180.40, Pesticide Residue Testing for Grain. (local file)

Soybean Protein & Oil

To provide information concerning intrinsic properties of soybeans related to user economics, GIPSA offers protein and oil testing of soybeans as an optional service. Protein and oil contents determine the amount and quality of end products, soybean meal and soybean oil, that can be produced from a bushel of raw soybeans. Upon request, GIPSA tests soybeans for their protein and oil content using Near-infrared Transmittance (NIRT). Using NIRT allows GIPSA to provide a simple, timely, repeatable and cost effective means of determining the oil and protein content in soybeans.

Soybean Cracked Seedcoats

The Soybean Cracked Seedcoats assessment was added to GIPSA's optional quality assessment services in response to increasing trade requests. The purpose of this test is to determine the percent of cracked seedcoats of sound soybeans. The determination is made on approximately 125 grams after the removal of foreign material and damaged kernels. Soybeans with cracked seedcoats are sound soybeans which have readily discernible cracked seedcoats, sound soybeans which have all or part of the seedcoat removed, or sound soybeans which are ¾ or more of a whole soybean.

The Soybean Seed Count assessment was added to GIPSA's optional quality assessment services in response to increasing trade requests for the service. GIPSA reports the number of whole soybeans contained in a specified weight. The determination of the seed count per gram is made on approximately 25 grams after the removal of foreign material and non-whole soybeans. This is then mathematically converted to the requested number per weight.

Soybean Seed Sizing

The Soybean Seed Sizing assessment was added to GIPSA's optional quality assessment services in response to increasing trade requests for the service. Seed sizing is a measurement of the percentage of soybeans passing through or remaining on top of a sieve size specified by the applicant for service. The test is run on a sample of approximately 125 grams after the removal of foreign material.

Soybean White Hilum

The Soybean White Hilum assessment was added to GIPSA's optional quality assessment services in response to increased trade requests. The purpose of this test is to determine the percent of whole soybeans with a clear white hilum. Upon request, tests for other hilum color (buff, brown, etc.) can be provided. The determination is made on approximately 125 grams after the removal of foreign material and non-whole soybeans.

TCK Smut Spores

GIPSA offers testing of wheat and other grains for the presence of TCK smut spores on an optional, for-fee basis. Both quantitative and qualitative services are available. Unless a qualitative analysis (screening for presence of TCK) is requested, quantitative analysis is provided. Quantitative analysis provides the actual number of spores per 50 grams.

TCK (Tilletia controversa Kuhn), also called Dwarf Bunt, is a smut fungus found in the soil or on the surface of wheat kernels. The organism only infects plants that grow during the winter. High levels of the disease are usually found after early and persistent snow cover. Wheat infected with TCK is obviously dwarfed in contrast to healthy plants and the inside of the kernel is converted into millions of fungus spores. The spores are not harmful to humans or livestock.

Original testing and appeal services are provided through the Wheat Marketing Center (WMC) laboratory in Portland, Oregon. GIPSA's Analytical and Testing Services Branch (ARTS) at the Technical Services Division in Kansas City provides oversight of the WMC. In addition, GIPSA's Analytical, Reference and Testing Services Branch performs any requested Board appeal services.

To request this optional testing service, contact your nearest GIPSA field office.

Vitamin Analysis

GIPSA offers testing for niacin in corn-soy blend upon request. Corn-soy blends are fortified through the addition of a vitamin premix of which niacin is a key ingredient. The amount of premix added is very small relative to the lot size. Therefore, it is essential that it be evenly distributed so as to produce a consistent product.  Niacin testing is provided by Analytical, Reference, and Testing Services (ARTS), a branch of GIPSA's Technical Services Division, at the GIPSA Technical Center in Kansas City, Missouri, using a high pressure liquid chromatography (HPLC) method.

Wheat Hardness

Kernel hardness is an important characteristic since it influences the way wheat performs during processing. It affects the way in which wheat must be (1) tempered; (2) the yield and particle size, shape, and density of flour particles; and (3) the end-use properties in milling, bread making, production of soft wheat products, and noodle-making.

GIPSA offers an optional wheat hardness test that uses specialized technology developed by the ARS Grain Marketing Research Laboratory in Manhattan, Kansas. The instrument analyzes exactly 300 kernels from a 15-20 gram portion of wheat which is free from dockage, shrunken and broken kernels, and foreign material. Individual kernel size, weight, crushing profile (hardness) and moisture are measured by the instrument, which then generates a histogram of values, including the range, average, and standard deviation for each of the four factors. Based on the sample's average hardness and distribution of single kernel hardness, the wheat is characterized as being Hard, Soft, or Mixed.

source: http://www.usda.gov/gipsa/programsfgis/inspwgh/other/qualityassessments.htm 22jan01

About the USDA GIPSA

Grain Inspection, Packers and Stockyards Administration

The United States Department of Agriculture’s (USDA) Grain Inspection, Packers and Stockyards Administration (GIPSA) facilitates the marketing of livestock, poultry, meat, cereals, oilseeds, and related agricultural products and promotes fair and competitive trading practices for the overall benefit of consumers and American agriculture. GIPSA is part of USDA’s Marketing and Regulatory Programs, which are working to ensure a productive and competitive global marketplace for U.S. agricultural products.

source: http://www.usda.gov/gipsa/aboutus/bkgd2.htm 22jan01