James Giese

It has been called the first recall of a U.S. food product containing a gene-modified ingredient not approved for human consumption. LABORATORY

The Food and Drug Administration announced on October 4, 2000 that it was officially recalling nearly 636,000 cases of Taco Bell brand taco shells sold in grocery stores. The agency announcement came nearly two weeks after Kraft Foods Inc., the manufacturer of the taco shells, launched its own voluntary recall of the product. The action was a Class 2 recall, defined as a situation where use of the produce may cause temporary adverse health effects.

The recall came about after a variety of an Aventis SA biotech corn was found in the taco shells. The corn was approved for use only in animal feed because of concerns that some people might be allergic to it. The corn uses a gene transplanted from a common soil microorganism, Bacillus thuringiensis (Bt), to make a protein that is toxic to certain insects. Federal regulators have approved several lines of so-called Bt corn for use in food. But this variety of corn, called StarLink, makes a unique toxin, Cry9C. This toxin has yet to be identified as not a potential food allergen.

The recall was precipitated when an anti-biotech environmental group found traces of the StarLink corn in taco shells purchased in suburban Washington, D.C. The recall brings up the issue of how companies can test and confirm if their products contain biotech ingredients or make sure their products do not contain these ingredients. There are two ways of doing this: identity preservation or finished product testing.

To keep crops straight—processors can make sure the crop is identity-preserved. This means that the identity of the crop is established at its origin and then traced from planting through harvest, distribution, processing, and labeling in a way that preserves the identity of the product throughout the entire process. This is difficult to do under current agricultural practices. However, identity preservation is useful to tout the added value of biotech crops.

For example, Cargill’s Illinois Cereal Mills (ICM), Paris, Ill., is launching a new brand of identity-preserved (IP) corn products and a system for producing such products called “InnovaSure™.” The system is designed to maintain the integrity of specialty whole corn, yellow goods, and masa through comprehensive procedures that start with the seed and continue through to customers’ doorsteps. Steps in the system involve: working closely with seed companies and customers to develop hybrids with the characteristics demanded by consumers; contract-growing all the corn and training growers in IP protocols; handling and storage in selected system elevators dedicated to IP corn; continuous in-house testing of product throughout the supply chain for such criteria as food grade starch content, genetic enhancement, and detection of foreign material; and providing full traceability and documentation on all products. For more information on this product, visit the InnovaSure web site at www.innovasure.com.

It is also possible to determine whether a food contains ingredients derived from biotech crops by checking a representative sample for novel DNA or its resulting protein.

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Currently, tests allow the detection of both proteins and nucleic acids. Specific DNA sequences in plant material can be detected using a technique called polymerase chain reaction (PCR). PCR requires specific DNA sequence information, which may be proprietary. The DNA is extracted from the ground sample. Then, primers are used to select only the DNA unique to the inserted genes. This DNA is then amplified in a cyclic reaction. In conventional PCR, these fragments of multiplied DNA are then separated on an agarose gel. The size and intensity of the DNA band(s) indicates the presence and relative level of targeted DNA within the sample. The conventional PCR technique is very sensitive, and can detect <0.1% biotech material in a sample (i.e., 1 bean in 1,000).

According to David R. Shipman, Grain Inspection, Packers and Stockyards Administration, USDA, in a speech given at Agricultural Outlook Forum 2000 entitled, “Testing for Biotechnology-Enhanced Grains and Oilseeds” (text of the speech can be found on the Web at www.usda.gov/oce/waob/oc2000/speeches.htm), newer PCR technologies have increased the sensitivity and reliability of PCR quantification beyond conventional methods. The newest innovation is referred to as real-time PCR. One important feature of this new technology is that the DNA amplification and analysis occur in the same reaction vessel, simplifying detection. Amplification of target DNA is measured via fluorescence during the PCR reaction. This technology can produce accurate quantitative results for as low as 0.01% biotech material. Real-time PCR is also more rapid (1-2 days) than conventional PCR (2 - 3 days), significantly decreasing the time needed for confirmation of positive results.

However, PCR is susceptible to errors due to contaminants, DNA breakdown, or improper implementation, and testing must be performed under rigorous laboratory conditions with appropriate controls. Personnel performing PCR assays must be highly skilled. Equipment for PCR testing is costly, ranging from $20-30,000 for conventional PCR to $60-100,000 for real-time PCR. For these reasons, PCR is not easily adaptable for rapid on-site testing at elevators or processing plants. Currently, PCR testing of crops and processed products for the presence of biotech products is offered commercially at a cost of $200-450 per test. The tests routinely take 3–10 days to get a result.

Novel proteins can be also detected in biotech crops and processed food fractions using ELISA (enzyme-linked immunosorbent assay) tests. ELISA tests analyze for a specific antibody reaction that marks the presence of the expected protein. Two types of ELISA kits are available: microwells and lateral flow or strip tests. Microwell kits are easy to use and can provide a semi-quantitative determination of GMO content. Results are obtained in 2-4 hours at a cost of approximately $2-20 per test. Lateral flow tests give qualitative results for GMO material in less than 20 min., at a cost of $1-5 per test.

According to Shipman, the level of detection ELISA tests varies for each product tested (due to differing levels of foreign protein in each product) and for each kit (due to the quality of the antibody). Current ELISA test kit manufacturers claim that the dipstick tests will reliably detect 0.1% GMO for Roundup Ready soybeans and 2% GMO for Bt corn. Caution must be exercised in interpreting ELISA test results. Quantification is difficult, as protein composition and expression levels for a given trait can vary widely.

The ELISA test allows testing at the first point-of-sale, enabling verification of identity on the spot by non-technical personnel. ELISAs are being marketed to seed developers, elevators, and processors both in the U.S. and abroad. Used as a risk management tool in conjunction with a segregation system, ELISAs can be highly effective when applied properly. Likewise, PCR testing is valuable for confirmation of sample identity and composition to facilitate final sale. When performed by a credible laboratory, PCR can be accurate, quantitative, and specific. More information on these types of tests may be obtained from Strategic Diagnostics Inc., Newark, Del., www.sdix.com.

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Method of and apparatus for automating detection of microorganisms. U.S. patent 6,122,396, filed 8/17/1999, issued 9/19/2000 to C. King and R. Hallowitz, assigned to Bio-Tech Imaging, Inc. Describes a unit for detecting microorganisms and consists of a fluorescence microscope section which is furnished with a motor-driven xyz stage for placing a slide sample subject to fluorescent staining. It also includes an illumination subsystem for projecting excitation light of predetermined wavelength on the sample and a filter assembly for emission, which limits the band of frequencies emitted to a video camera which captures the images of fluorescent stained microorganisms from the sample slide mounted on the stage. A computer reads the output value of the band-limited signal from the video camera and processes the read output. A subsystem device has controllers, which drive the stage so as to permit the microorganism sample to be scanned over its whole area. Each image is displayed on a video display monitor and detected microbes in the sample are stored on a hard drive and in an imaging archive system to permit verification or reexamination.

Products & Literature
MINI DIGITAL REFRACTOMETER, Model 502246, may be used to measure Brix from 0 to 45% with 0.1% resolution in fruit, soft drinks, wine, and other liquid food products. The refractive index measurements range from 1.3330 to 1.4100. Temperature measurements range from 0 to 40°C with 0.1°C resolution. The display provides units in Brix (%), refractive index (nD), energy Kcal per 100g solution (Cal) or temperature (oC). Features include a built-in, easy-to-clean prism with cover, automatic temperature compensation, zero adjustment function, and auto power off. Error messages inform the user if the battery is low, the meter needs recalibration, or the temperature is outside of range. For more information, contact Extech Instruments Corp., 285 Bear Hill Rd., Waltham, MA 02451-1064 (phone 781-890-7440; fax 781-890-7864) —or circle 300.

STEAM STERILIZERS are available in 17, 19, 23, 50, 65, and 140 L capacities. The autoclaves are microprocessor controlled and have inner and outer walls made in AISI 304 stainless steel for long shelf-life. The units have front panel instructions for operator convenience and safety. For more information, contact International pbi, Spa., Via Novara, 89, 20153 Milano, Italy (phone 39-02-48-779-1; e-mail [email protected]) or circle 301.

GAS CHROMATOGRAPH/MASS SPECTROMETER, the Saturn 2100, is said to be an economical unit that will meet the requirements of most GC/MS methods. The instrument features a new split/splitless injector with electronic flow control, which allows pressure pulse injections and constant flow reparations. It has a smaller GC oven that still accommodates standard capillary columns and provides improved access to the injector for faster routine maintenance. The system can be outfitted with an autosampler with 100-vial capacity. For more information, contact Varian, Inc., Marketing Dept., 2700 Mitchell Dr., Walnut Creek, CA 94598 (www.varianinc.com) —or circle 302.

FILTRATION UNIT, the UOP 12, is a pilot-plant scale instrument allowing investigations into filtration. It is a bench-top unit designed to introduce students to the fundamentals of solid/ liquid filtration. It demonstrates the principles of batch filtration using a fully functional plate and frame filter system with an optional continuous tangential flow microfiltration unit using a hollow fiber filtration cartridge. Both types of filter are widely used in industry. The filter is clear acrylic so students can see the whole filtration process. The practical training exercises included are appropriate to chemical and all other process-related engineering courses. An economic investigation allows the student to take experimental data and use it to help make decisions on the size and operation of a filtration plant to meet economic and output targets. An optional interface is available to allow linking to a personal computer. For more information, contact Armfield, Inc., 510 N. Main St., Denison, IA 51442 (phone 712-263-5885; fax 712-263-8884; www.armfield.co.uk) —or circle 303.

MASS SPECTROMETER, the PerkinElmer-Bruker Daltonics OmniFlex™ Matrix-Assisted Laser Desorption Ionization-Time-Of-Flight Mass Spectrometer, may be used in quality control and production testing applications in the biotechnology and dietary supplement industries. The unit is said to provide the sensitivity, resolution, and mass accuracy of larger and more complex systems in a benchtop model. For more information, contact Perkin Elmer Instruments, 761 Main Ave., Norwalk, CT 06859-0226 (phone 203-762-4003; fax 203-761-2898; www.perkinelmer.com) —or circle 304.

ORGANIC ANALYZER, the OptiQuant™, may be used to continuously monitor chemical oxygen demand, biological oxygen demand, and total organic compounds. The unit is said to be ideal for use at each stage of the wastewater treatment process for measuring residual organics in drinking water or monitoring industrial water to ensure that it is free of organics–such as PCBs and chlorofluorocarbons. The analyzer uses ultraviolet light absorption technology and does not require reagents or sample conditioning. It has a self-cleaning probe. The instrument’s stainless-steel probe detects UV absorption of organics with a dual-beam photometer that automatically compensates for turbidity. For more information, contact Hach Co., P.O. Box 389, Loveland, CO (phone 800-227-4224 or 970-669-3050; fax 970-669-2932; www.hach.com) —or circle 305.

Associate Editor