Paula M. Powell, Senior Editor
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: [email protected].