Evaluation of Fructooligosaccharides and Inulins as Potentially Health Benefiting Food Ingredients by HPAEC-PED and MALDI-TOF MS

This paper describes the complementarity of high-performance anion exchange chromatography coupled with pulsed electrochemical detection (HPAEC-PED) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) to evaluate commercial available fructans (fructooligosaccharides (FOS) and inulins), having different degrees of polymerization (DP) which are usually employed by food industry as functional ingredients either for their prebiotic properties or as a fat replacer, giving a fat-like mouth feel and texture. The developed HPAEC-PED methods are able to analyze FOS (fructans with DP 3–10) and inulins (DP ranging from 3 to 80) with a good resolution and relatively short retention times to evaluate structural differences between fructooligosaccharide and inulins and the possible presence of inulooligosaccharides as well as of branching. To characterize FOS and inulin at different degrees of polymerization and to assure correct molecular assignment, MALDI-TOF MS analysis was also investigated. The 2,5-dihydroxy benzoic acid (2,5-DHB) was found to be the best matrix for FOS analysis as Actilight and Raftilose P95 products, while 3-aminoquinoline (3-AQ) seems to be the best matrix for inulin with higher DP. The applicability of the optimized methods to the identification and determination of FOS contained in a symbiotic milk as well as a type of inulin added as functional ingredient to a cooked ham is demonstrated

Caratterizzazione di carboidrati come marker di qualità, di processo e di tipicità degli alimenti mediante l'ottimizzazione e la validazione di metodi HPAEC-PAD

Questa tesi di dottorato riguarda lo sviluppo e la validazione di metodi mediante cromatografia anionica ad alte prestazioni con rivelazione amperometrica pulsata (HPAEC-PAD) utilizzati per l'analisi di carboidrati di interesse alimentare. Lo studio è stato condotto inizialmente su carboidrati semplici e complessi in alimenti quali ad esempio pasta e leguminose al fine di impiegarli quali possibili markers di qualità e di processo. Successivamente sono state analizzate fibre solubili con proprietà prebiotiche denominate fruttani ed è stata verificata la loro sicurezza alimentare tramite analisi del contenuto di nitrati. Al fine di caratterizzare i fruttani in alcuni alimenti sono state ottimizzati e confrontati sia metodi HPAEC-PAD che di spettrometria di massa (in particolare MALDI-TOF-MS), che sono risultati complementari per l’analisi della frazione oligo e polisaccaridica dei fruttani. Parallelamente è stato condotto uno studio sulla risposta del rivelatore amperometrico pulsato in relazione al grado di polimerizzazione delle fibre alimentari solubili analizzate. Tale indagine ha permesso di effettuare analisi quantitative di fruttani naturalmente presenti negli alimenti (ad esempio nella cipolla) o aggiunti come ingredienti funzionali (ad esempio latti fermentati e prosciutti cotti). Infine sono state effettuate analisi chemiometriche per la caratterizzazione di cipolle di differenti varietà e origine geografica mediante il profilo cromatografico.This PhD thesis concerns the development and validation of high performance anion exchange chromatography with pulsed amperometric detector (HPAEC-PAD) methods for the analysis of carbohydrates of food interest. The study was initially conducted on simple and complex carbohydrates in foods such as pasta and leguminosae in order to employ them as potential markers of quality and process markers. Subsequently, soluble fibers with prebiotic properties, named fructans, have been analyzed and their food safety has been verified by nitrate analyses. With the aim to characterize fructans in some foods, HPAEC-PAD and Mass Spectrometric (in particular MALDI-TOF-MS) methods have been optimized and compared for the analysis of fructans oligo and polysaccharidic fractions. In parallel a study about the pulsed amperometric detector response was conducted in relationship with the degree of polymerization of the soluble dietary fibers analyzed. This survey has allowed to perform quantitative analysis of fructans naturally present in foods (such as in onion) or added as functional ingredients (e.g. fermented milks and cooked ham). Chemometric analyses were also performed for the characterization of onions of different varieties and geographical origin by the chromatographic profile