Recent advancements of EC-QCL based mid-IR transmission spectroscopy of proteins and application to analysis of bovine milk

KULIGOWSKI, JULIA; SCHWAIGHOFER, ANDREAS; LENDL, BERNHARD; ALCARAZ, MIRTA RAQUEL

Amsterdam

Conferencia; The 17th European Conference on the Spectroscopy of Biological Molecules; 2017

AbstractBACKGROUND: High emission powers of external cavity-quantum cascade laser (EC-QCL) light sources allow to employ significantly larger path length for infrared (IR) transmission measurements compared to conventional Fourier-transform infrared (FTIR) measurements employing thermal emitters.OBJECTIVE: An EC-QCL based IR transmission setup is presented as a viable alternative for analysis of proteins in both, academic protein structure studies as well as in process analytical applications. The 4-5 times higher applicable transmission path length allows robust measurements of the protein amide I band. Here, the application of EC-QCL based IR transmission spectroscopy is introduced for rapid screening of the thermal history of commercial milk samples without prior sample preparation.METHODS: Proteins present in milk were measured by QCL-IR and FTIR spectroscopy and spectra were compared. Dynamic conformational changes were followed by QCL-IR spectroscopy after chemical denaturation. Sixteen commercial milk samples were surveyed by QCL-IR spectroscopy and classified according to the experienced heat load during processing.RESULTS: A classification analysis of commercial bovine milk samples based on their thermal history was accomplished. Furthermore, it was shown that IR spectra of the protein amide I band acquired by EC-QCL transmission spectroscopy are comparable to FTIR spectra.CONCLUSIONS: The potential application as a fast screening method for estimating the heat load applied to commercial milk is demonstrated.