Stuff assorted meat products, salt, potassium lactate, flavoring, hydrologized beef stock, sodium phosphate and sodium nitrite into a casing of ambiguous origin, and you have a preservative-laden hot dog that could probably last for years. Nevertheless, vendors still want to protect that dog with wrappers that also withstand the elements. Now they have a little more test and analysis help from fast IR imaging. According to scientists at Digilab Inc., the process, which extends the capabilities of the IR microscope, can collect a 600-μm2 image in 20 seconds, using a focal plane array detector to collect up to 65,000 individual IR spectra simultaneously. The system features spatial resolution approaching 5 μm and a high signal-to-noise ratio because each detector element or pixel is fully illuminated. And, because a spectrum correlates with each pixel of the array, end users can rapidly examine the distribution of components within packaging as well as in a variety of foods. In fast IR imaging, wrapper images generated from three wavelengths highlight different positions and, thus, different polymers in the wrapper. “Food wrappers in general have several layers,” said Norman Wright, Digilab applications manager. “The goal is to protect what’s inside from the outside environment and what’s outside from what’s inside, with both issues related to moisture and odor concerns.” He added that wrappers also require strength and flexibility. Typical layers providing these properties are polyethylene, polypropylene, ethylvinylacetate and polyamide. In the application for the hot dog vendor, the inspection system generated wrapper images from three wavelengths, highlighting different positions and thus different polymers in the wrapper. A benefit of the fast IR imaging process is that using a variety of stains to identify components is unnecessary. The natural chemistry of the material and the IR spectrum associated with each component act as the stain. Wright said that inspection costs drop because it is no longer necessary to use a step-scan spectrometer. End users can collect all data in rapid-scan mode using a Fourier transform IR spectrometer, a microscope and an IR array detector with 32 x 32- or 16 x 16-pixel format. Contact: Norman Wright, Digilab Inc., Spectroscopy Div., Randolph, Mass.; +1 (781) 794-6400; e-mail: norman_wright@digilabglobal.com.