Food Safety Magazine, August/September 2011

Surface-Enhanced Raman Spectroscopy (SERS)

Dr. Labuza realized that the threat to
milk could be minimized if he, Dr. Lili
He, and his research team developed
a quick and accurate way to test
each batch of milk as it arrived at the
processing plant—and this is why he
turned to surface-enhanced Raman
spectroscopy (SERS). SERS, as Dr.
Labuza explains, is a “simple, robust,
and quick assay method” and could
be used for “detecting important bio-
logical or chemical agents,” meaning
anything from melamine, to com-
monly available insecticides such as
malathion and diazinon, to difficult-to-
obtain but deadly fungal by-products
such as aflatoxin, ricin, and others.

Adsorbed Analyte

Thermo Scientific DXR Raman Microscope

In a “proof of concept” laboratory experiment, Dr. Labuza’s research team added ovalbumin (egg protein) to milk. Using standard enzyme-linked immu-

532 nm ExcitationSurface Plasmons Silver Surface Raman Scattering

nosorbent assay (ELISA) techniques, the ovalbumin was captured and then the captured proteins were dropped onto special, prepared silver dendrite plates that present a nano-structured SERS active surface. These plates were then inserted into a Thermo Scientific DXR Raman microscope for analysis. The DXR, says Dr. Labuza, is “simple to use” and, because most of the functions are fully automated, “you can teach someone how to use it in half an hour.” He also likes the ability of the DXR to distinguish between very similar molecules, such as proteins, using its built-in principal component analysis (PCA) software, as well as its ability to analyze multiple plates. The whole process, from sampling the milk to characterizing the contaminant (to the microgram/milliliter level), he says, can be completed in less than 30 minutes.

Food Defense in the Future

With continued funding for his research, Dr. Labuza wants to create a simple laboratory kit (a test plate) that will capture a large variety of potential contaminants from milk, and then use a hand-held SERS device to analyze the test plate for the presence of any potentially harmful compounds. This, he says, would fulfill the DHS requirement for an analytical technique that is both quick and robust, allowing milk processors to screen incoming milk before products are made. The ability to analyze milk at such an early stage in the process would be an important step to ensuring product safety without having to rely solely upon downstream laboratory testing.