VIS/NIR Spectroscopy Spots Adulterated Crabmeat

Anne L. Fischer

One way that food manufacturers may seek to boost profits is to add inferior ingredients to high-end products. Doing so generally does not pose a health hazard to consumers, but the failure to correctly identify ingredients defrauds customers and undercuts legitimate industry prices.

To address this economic adulteration in seafood, researchers at North Carolina State University in Raleigh and at Florida Gulf Coast University in Fort Myers have used visible and near-infrared spectroscopy to detect the presence of surimi, an inexpensive whitefish filler, in samples of crabmeat.

Samples of two types of crabmeat were adulterated in 10 percent increments with surimi, an imitatin crabmeat made from whitefish. The samples were blended and stored in plastic bags for subsequent analysis by VIS/NIR spectroscopy.

Previously, such inspection involved more expensive methods such as gas chromatography and mass spectrometry. The researchers chose to use VIS/NIR spectroscopy because the technique requires minimal sample preparation and does not damage the sample.

They used two types of crabmeat in the investigation: Atlantic blue and an imported blue swimmer. They adulterated samples of each with surimi in 10 percent increments from 10 to 90 percent. They examined pure crab, adulterated crab and pure surimi with a Foss NIRSystems 6500 spectrometer, collecting spectra from 400 to 2498 nm at 2-nm intervals. For each sample, the recorded spectra consisted of an average of 32 scans. Each was randomly scanned four times and averaged to obtain the new data set.

The spectra showed a decrease in absorbance values as adulteration increased. By analyzing the spectral changes via chemometrics, the researchers identified and predicted adulteration.

According to Scott A. Hale, professor in the department of biological and agricultural engineering at North Carolina State, both the visible and near-IR techniques equally identified adulteration. The group is now working on feasibility studies and plans to put together a package to deal with species, quality and authenticity issues that might become a commercial inspection tool.

Journal of Agricultural and Food Chemistry, online Jan. 31, 2006, doi: 10.1021/jf051636i.