Characterization of morphological changes to an epoxy-based polymer used as a corrosion-preventative lining in retorted canned tomatoes

This study investigated how heat-induced changes to compounds in tomatoes initiated morphological changes to the lining in metal cans. X-ray diffraction, Fourier transform near-infrared spectroscopy, and scanning electron microscopy characterized these morphological changes and we investigated the elemental composition of the lining in the cans before and after heat processing. All tomato-filled cans were sealed, retorted (121 °C, 30 min), then stored at 49 °C for 50 days. Selected-ion flow-tube mass spectrometry then measured the concentrations of volatile compounds in the polymeric linings of unprocessed and processed cans. Results showed that thermal degradation of amino acids in the tomatoes gave rise to volatile methyl sulfides that were subsequently sorbed by the can linings. This process caused breaches in the lining, moisture uptake by the polymer, delamination, and exposure of the base-metal in the cans. These effects allowed electrolytes in the tomatoes to initiate corrosion in the wall of the cans.