Aplicación de la espectroscopia de resonancia magnética nuclear al análisis de embutidos
The present doctoral thesis focuses on the application of medium field (400 MHz) nuclear magnetic resonance (NMR) spectroscopy to the analysis of the fatty fraction of dry sausages, such as chorizo. NMR spectroscopy is known to be advantageous in fat analysis such as oil; however, high field NMR or derivatization strategies must be considered in order to achieve its full potential. Our work aims to optimize the methodology of analysis in order to make it feasible for routine analysis of fats. Challenges such as detection limit and signal overlapping were overcome by means of adjusting adquisition parameters (number of scans, relaxation delay and heteroatom broadband decoupling) Additionally, a big improvement in resolution was achieved when using solvent mixtures involving hexadeuterodimethyl sulfoxide. The new methodology allows the detection and quantification of diacylglycerides, monoacylglycerides, free fatty acids, and other minor components in one single, short experiment, as well as the characterization of the main constituents of the fat. We analyzed the evolution of chorizo fat along the whole ripening and storage time in actual manufacturing conditions. We compared the evolution of different batches of chorizo, including both minor composition changes (salt reduction, antioxidant addition) as well as major composition changes (meats from different breeds). We corroborated that the nature of meat affected the lipolysis evolution more than changes in ingredients. In conclusion, this optimized analytical NMR methodology is simple and straightforward and can be easily applied to the monitoring of the evolution of dry sausages throughout the whole manufacturing process.
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