Photonics Food Detectives

Paula M. Powell, Senior Editor

Whether inspecting for E. coli O157:H7 on a slab of beef or for ethylvinylacetate in a hot dog wrapper, manufacturers in the food processing industry are turning more and more to photonics for help — and not just for laboratory-based detective work. Increasingly, IR detectors and other photonics-based instruments are making their way into the field. From farmers who are producing genetically modified grains to beef inspectors, the draw is a combination of system compactness and testing speed.

Often, politics fuels the demand for inspection tools, from laser-diode-based biosensors to spectrometers. Consider the Meat and Poultry Products Safety Improvement Act of 2002 sent recently to the Senate Agriculture Committee. One component is the need for high-speed detection of chlorophyll on carcasses, which could indicate the presence of E. coli. A possible solution detects fluorescence of gastro-intestinal tract digestive metabolites, from chlorophyll to enzymes, using a detector held close to the carcass.

Another political hot spot, especially for the European Union, is genetically modified food. Researchers at the Grain Quality Laboratory in Ames, Iowa, believe that near-IR spectroscopy could provide a nondestructive testing technique that is lower in cost and less time-consuming than those now used. Although not able to detect compounds at the DNA concentration level, a portable spectrometer might be able to spot spectral differences from larger structural changes.

And then there’s the US-based researcher who believes that IR imaging may someday be able to spot whether an apple is sweet. Although this research is still preliminary, several photonics-based tools — including machine vision-based systems — are either already in the field or in beta testing, as illustrated by the applications that follow.