A national restaurant chain received a complaint from a customer about an unidentified green material found on a piece of bread used in a top selling menu item. To adequately address the complaint, the restaurant needed to identify the green material and determine if their product had been tampered with or if the issue was the result of problems with preparation, packaging, or processing.
Examination of the green material was conducted utilizing polarized light microscopy (PLM), scanning electron microscopy (SEM), coupled with energy dispersive x-ray spectrometry (EDS), and by micro-Fourier infrared spectrophotometry (micro-FTIR).
The foreign green material was concentrated locally in the bread interior with only a small portion exposed at the surface, and was found to be associated with a stain or dye as opposed to discrete individual particles.
The foreign green material appeared to be a stain or dye locally concentrated in the interior bread layer indicating that contamination occurred during mixing and prior to baking. Trace quantities of dyes are often all that are necessary to impart color to a variety of products. Based on this information, the restaurant was able to successfully trace the problem back to the baker that supplied their bread.