Depth profiling of a heterogeneous food-packaging model using step-scan Fourier transform infrared photoacoustic spectroscopy Original Research Article

Fourier transform infrared (FTIR) spectroscopy with a photoacoustic (PA) detector was used to study a multi-layer starch–protein–polyethylene composite system. Non-destructive depth profiling was performed to identify the spectral peaks corresponding to the absorbing chemical groups of the individual components that reside in the respective layers. Well-separated peaks corresponding to starch, protein, and polyethylene were obtained from the FTIR-PA spectra. The analysis was confirmed by comparing the peaks from the composite layers with the peaks of the individual components. Overlapping peaks that correspond to protein and starch in the mid-infrared region were resolved using the generalized two-dimensional (G2D) correlation analysis for spectra enhancement. The study indicated that a starch–protein composite system wrapped in a polymer package could be non-destructively identified using FTIR-PA spectroscopy with G2D analysis.