Ensuring Accurate Labeling of Processed Fish Products

In recent years the variety of fish products available to consumers has grown dramatically, ranging from low-cost frozen fish sticks to premium-grade fish steaks. However, recent studies suggest the type of fish described on a product's label may not be in the package—a practice that is illegal in the U.S. and elsewhere.

To improve compliance with labeling laws, some regulatory agencies want to enhance their ability to verify the origin and authenticity of the fish used in consumer products. Visual identification based on physical characteristics works well with whole fish but becomes less reliable as fish are processed. Because genetic material remains detectable in all but the most heavily processed products, DNA-based methods can provide consistent, repeatable identification of fish species virtually anywhere along the processing chain.

Improving resolution and detection

Direct sequencing of DNA is the most definitive approach but, unfortunately, it cannot be easily applied to products that contain more than one type of fish. One alternative is polymerase chain reaction (PCR), which can handle mixed samples and identify individual species through their DNA profiles. An extension of PCR that adds restriction fragment length polymorphism (PCR-RFLP) has been used successfully for identification of salmon species.

In research funded by the British Food Standards Agency, Steve Garret and John Dooley from Campden & Chorleywood Food Research Association further developed the PCR-RFLP method for identification of 19 commercially important species of salmon and white fish. The relevant measurements were performed using the Agilent 2100 bioanalyzer and DNA 500 LabChip kit.

The results of that work are documented in the Agilent application note "Determination of PCR-RFLP Profiles for Fish Species Using the Agilent 2100 Bioanalyzer." The bioanalyzer generated precise, consistent results for a variety of samples and was able to clearly differentiate between the tested species. Compared to traditional slab gel electrophoresis (SGE) methods, the bioanalyzer produced profiles with improved fragment resolution and detection—and revealed fragments that SGE missed. The resulting DNA profiles were also more consistent than with SGE.

Further studies that expand the number of species in the analysis database will enhance this method's ability to check the veracity of fish-product labels and give consumers greater confidence in what they're buying.

For more information

To learn more about related applications, please see the Genomics and Foods & Flavors pages. For additional information about these and other Agilent life sciences products and resources, please visit the Life Sciences/Chemical Analysis main page.