Roberto Megias Perez

• The present thesis reports the development and use of chromatographic techniques coupled to mass spectrometry for the characterization of low molecular weight carbohydrates (LMWC) in dietary foods of economic relevance or identified as “functional food”. The interest for the analysis of LMWC in different dietary foods is based on the involvement of these compounds in biological reactions in plants and the bioactive properties reported for some LMWC. A general overview of the carbohydrates, the analytical methodologies to perform their analysis and a brief description of the different dietary foods selected for this study (cocoa beans, commercial green tea and kale) are reported in the different chapters (chapter 1-3) of the introduction. The study of LMWC in cocoa beans includes three chapters (chapter 4-6). The content of chapters 4 and 5 is a comprehensive characterization of the LMWC profile in cocoa beans using HILIC-ESI-TOF MS, HILIC-ESI-MSn and GC-MS, the quantification of the main and minor LMWC from different origins and a proposal of different indicators of fermentation. Chapter 6 covers a detailed chemometric and kinetic approach to monitor the LMWC changes during the spontaneous fermentation of cocoa beans. The study of commercial green tea (chapter 7) evaluates the LMWC together with other physical and chemical established quality indicators (soluble solids, color and antioxidant capacity) to characterize CGT. This approach has resulted to be useful for the characterization of the samples according to the type of processing employed during the manufacturing. Chapter 8 reports the identification for the first time of different LMWC in kale. This chapter also includes the analysis of the LMWC content in three types of kale during the development of the plant, as well as the monitoring of the changes produced as a consequence of cold temperature during farming.