NUOVI METODI ANALITICI PER MIGLIORARE IL CONTROLLO DI QUALIT\uc0 DEL CAFF\uc8

Il caff\ue8 \ue8 la bevanda pi\uf9 commercializzata al mondo, e il suo consume ha visto un sorprendente sviluppo nel corso dei secoli. Il controllo della sua qualit\ue0 \ue8 per questo di grande importanza, in ogni fase del processo produttivo. Lo scopo di questa tesi \ue8 quello di presentare il nostro contributo al miglioramento del controllo della qualit\ue0 del caff\ue8. Met\ue0 del lavoro qui descritto \ue8 stato svolto in ambiente industriale, presso Aroma Lab di illycaff\ue8 e presso Demus Lab S.r.L. L\u2019altra met\ue0 \ue8 stata invece svolta in ambiente accademico, presso il Dipartimento di Scienze Chimiche e Farmaceutiche dell\u2019Universit\ue0 di Trieste, e presso la School of Biological and Chemical Sciences all\u2019Universit\ue0 Queen Mary di Londra. L\u2019arogomento principale \ue8 stato la differenziazione tra le due principali variet\ue0 di interesse commerciale presenti sul mercato, Coffea arabica e Coffea canephora, perseguita in due modi: \uf0b7 Attraverso la sintesi di polimeri ad imprinting molecolare specifici per il cafestolo e per il 16-metil-cafestolo. E\u2019 noto che queto composto \ue8 presente solo in robusta mentre il cafestolo \ue8 presente in entrambe le variet\ue0 di caff\ue8. I due terpeni sono stati isolati e purificati da campioni di caff\ue8 robusta tostato, e sono stati identificati monomeri funzionali capaci di interagire con i due composti in maniera selettiva. Si \ue8 scelto l\u2019approccio dell\u2019imprinting covalente, e per il cafestolo sono stati sintetizzati boronati polimerizzabili, in quanto la molecola contiene un raggruppamento diolico. Il 16-metil-cafestolo \ue8 stato invece utilizzato per ottenere suoi esteri polimerizzabili con acidi cinammici. Sono stati quindi sintetizzati polimeri ad imprinting sotto forma di nano/microgel in condizioni di alta diluizione. I polimeri sono stati caratterizzati per quanto riguarda le loro propriet\ue0 fisiche e la loro capacit\ue0 di rilegare selettivamente le due molecole, con promettenti risultati. \uf0b7 Attraverso lo sviluppo di una metodologia analitica colorimetrica per quantificare la composizione di miscele di arabica e robusta. La metodologia prevede l\u2019utilizzo di antimonio cloruro su estratti di caff\ue8 in solventi non polari. Negli spettri UV-Vis degli estratti trattati si ritrovano due picchi caratteristici a 726 nm ed a 819 nm per robusta e arabica rispettivamente. Il sistema permette la quantificazione di robusta in arabica con ottima sensibilit\ue0. \uf0b7 Inoltre, durante il periodo svolto presso Demus Lab, \ue8 stato sviluppato un metodo HPLC-UV per la quantificazione dell\u2019acrilamide nel caff\ue8 tostato.The differentiation between the two species is gaining attention, since Arabica is, due to giving a beverage with a superior taste, far more popular than Robust. As Arabica occupies more than 75% of the global coffee market while being about twice as expensive as Robusta, and as the beans of both species are visually relatively similar, often leads to fraudulence. Differentiating between the beans of both species by eye or under a microscope is generally possible, but it yields biased results and is deemed unpractical on the large scales of coffee production. Search for chemical markers of authenticity of Arabica is on the rise, as their analysis would give far more reliable results. Currently developed methods, however, often require tedious and time-consuming sample preparation techniques and analysis using expensive laboratory equipment. One of such analytical methods is the DIN 10779 method for quantification of 16-O-methylcafestol (16-OMC) in coffee, a marker to determine the degree of contamination of Arabica with Robusta. 16-OMC is a diterpene alcohol, found in significant amounts in the beans of Robusta coffee and in minor amounts in the beans of Arabica. Structurally, it is similar to cafestol, with the only difference on the carbon 16, where a methoxy group can be found in 16-OMC and a hydroxyl group in cafestol. The DIN 10779 method consists of Soxhlet extraction and saponification of coffee oil, followed by HPLC-UV analysis. By creating a selective molecularly imprinted polymer for 16-OMC, we wanted to simplify its extraction from the coffee matrix, and possibly try to integrate the imprinted material into a sensing device in the future. Namely, imprinted polymers are essentially highly selective porous materials, cross-linked around the template molecule. Thus, molecular memory is introduced into the structure. Upon the removal of the template selective rebinding of the target molecule is possible. As a significant amount of cafestol is present in the beans of Arabica and Robusta, we decided upon synthesis of imprinted polymers for both diterpenes. Having the information on their content in the coffee extract could give us a more precise information on the degree of contamination of Arabica with Robusta. First, the diterpenes were isolated from roasted and ground Robusta coffee beans. Appropriate functional monomers were selected to gain optimal molecular recognition for each diterpene. Upon synthesizing the polymerizable derivatives for both, a palette of imprinted polymers was synthesized via high dilution radical polymerisation. Covalent imprinting was attempted, as thusly synthesized polymers usually exhibit a more specific rebinding. The polymers were characterized and based on the results of the rebinding studies, the most perspective ones were determined. Upon preliminary studies, chloroform and dichloromethane extracts of Robusta and Arabica have been found to give a characteristic colour when treated with a 30% solution of antimony(III) chloride in chloroform. In the UV-Vis spectra of the treated extracts, peaks at 726 nm and 819 nm were found, the first being characteristic for Robusta and the second for Arabica. With further optimisation of the preparation of coffee extracts, composition of the antimony(III) chloride solution, kinetic studies and selection of a working wavelength, a simple, fast and reliable method for quantification of contamination of Arabica with Robusta coffee was developed. Our final contribution to the improvement of quality control of coffee was development of an HPLC-UV method for quantification of acrylamide in roasted coffee, in collaboration with Demus Lab S.r.l