This research project addresses three independent studies that are related to the authentication of olive oil and sherry wine vinegar through the usage of UV-Vis spectroscopy. In the first study, an adulteration study was carried out in olive oils by using colored vegetable oils with natural colorants.. Two different procedures were developed aiming at detecting the falsification. The second study presents a novel method based on the standard deviation of normalized spectra at adequate wavelengths. This method has provided an accurate resolution of spectra at individual components in a two-component system which can be used for multicomponent systems with bigger sizes. The method then was effectively applied to different olive oil sets. Finally, the third study was performed in order to determine the characterization of sherry wine vinegars. For the first time, chromatic parameters were used for characterizing sherry wine vinegar according to the type of the wine used and the acetification process followed during the elaboration process. Once again, the results were satisfactory. The UV-Vis spectroscopic technique has been proven to be a versatile tool for a rapid and nondestructive analysis in oil and vinegar samples based on the study of their spectra.