Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine UNIVERSITY OF UDINE ________________________________________ FACULTY OF AGRICULTURE Doctoral course in Food Science Department of Food Science (Course XXIV) DOCTORAL DISSERTATION Effects of Origin and Treatment of the Roasting Process on the Aromatic and Sensorial Composition of Coffee Ph.D. Course Coordinator: Prof. Alessandro Sensidoni Ph.D. Supervisors: Prof. Roberto Zironi Ph.D. student: Dr. Giovanni Mastronardi ACADEMIC YEAR 2011-2012 Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine UNIVERSITY OF UDINE Faculty of Agriculture Doctorate in Food Science XXIV cycle This thesis is presented By Giovanni Mastronardi and approved by the Supervisor: Prof. Roberto Zironi Department of Food Science University of Udine Giovanni Mastronardi, Doctoral Dissertation: Effects of Origin and Treatment of Roasting Process on the Aromatic and Sensorial Composition of Coffee. I Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine ACKNOWLEDGMENTS Many thanks to Professor Roberto Zironi and Dott. Franco Battistuta, my major advisors. They have not only supported me with encouragement and challenges, but have also been exceptional mentors and friends. I would also like to thank my colleagues who have helped me in many situations: dr. Piergiorgio Comuzzo, dr. Lara Tat, dr. Stefano Micolini, dr. Laura Brotto, dr. Sergiu, dr. Deborah and all the others, Paolo, Stefano, Lorena, Milena, Matteo, Lavinia and ACAUD association for my sensorial analysis. I want to extend my gratitude to Dott. Alessandro Rettore, general manager Julius Meinl and quality manager Dott. Sonia Castracane who gave me opportunity to provide coffee samples and analysis support together with Ugo, Michele, Giovanna, Federico and Massimo. I would also like to thank Luigi Pallotti manager at Pura Vida Cafè and Alberto Polojaz manager at Imperator coffee who gave me help and support in organizing sensory analysis and panel (judges) training for my project. Finally thanks to my parents, Vito and Nicoletta my sister Michela my grandmother Margherita, who gave me a solid foundation not only for academics, but also for life and love. Giovanni Mastronardi, Doctoral Dissertation: Effects of Origin and Treatment of Roasting Process on the Aromatic and Sensorial Composition of Coffee. II Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine ABSTRACT The quality of espresso coffee generally arises from raw quality (genetic factors, typical of species and variety, soil, weather, agronomic processing, post harvesting processing) and roasting degree. From the ripe coffee cherry to roasted coffee roasting is the most important step in the processing chain. Physical and chemical properties of roasted coffee are highly influenced by process conditions during roasting, in particular by the time- temperature parameters (roast curve) within the coffee bean as a function of heat transfer. Chemical changes take place during the roasting process and reaction pathways lead to the formation of a wide range of volatile organic compounds that are quite abundant in coffee headspace. Numerous publications have appeared on the nature of reactions leading the roasted coffee flavour explaining that there are several hundred volatile compounds identified in coffee. Around 30 of these have been identified as aroma impact compounds. Scientific information on how new technologies affect the aroma quality of coffee roast and the brewed beverage is poor and sometimes contradictory. This scientific work was sampling of different single coffee raw and for every coffee was roasted with degree roast light, medium and dark. There were three replicates for treatment. The first step of the current work was the identification of the different provenance of 6 Arabica raw coffee samples and their “quality markers” analyzing thoroughly the respective peculiarity. This study had the merits of identifying the volatile compounds of single green coffee and so in this way, it was possible to conclude how the different provenance had present a strong influence on the chemical compounds affecting the final quality. Investigation of potent odorants from green coffees was performed using head space solid-phase microextraction in conjunction with gas chromatography-olfactometry. The second step of the current work was the identification of aroma compounds in roast coffee. All trials were run to an equal roast end point as defined by the lightness of coffee beans. The raw Arabica samples were roasted Giovanni Mastronardi, Doctoral Dissertation: Effects of Origin and Treatment of Roasting Process on the Aromatic and Sensorial Composition of Coffee. III Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine to 3 different roast degree (light, medium, dark). The developing aroma compounds profiles were characterized by gas chromatography, mass spectrometry, and olfactometry. Another objective of this work was to verify how different roasting processes might affect sensory properties of coffees of different provenience. The third step was to identify the possible molecules called quality of “markers” able to correlate positively the singles roasted coffee based on the composition of the volatile fraction and the overall point of view of the sensory analysis. The main goal was to investigate, also the evolution of classes aroma compounds during roasting under with different time conditions and to compare experimental results with sensory analysis of espresso coffee. The results were evaluated by statistical analysis using PCA, Cluster Analysis, and Variance analysis. It was observed that the aromatic profile of roasted coffee was totally different from raw coffee, and comparing different roasted coffee the effect origin green coffee results more important than effect treatment roasting. As a result of sensory analysis together with analytical valuation of the aroma compounds, there are several behavior of the coffees tested in relation to the roasting degree and the provenance. Moreover 19 note odours, possible “markers” were identified for all samples describing the coffee aroma in accordance with a few odours reported in literature. These possible “markers” provided sufficient differentiation for coffee samples of different origin and roasting treatment. The “markers” also present a good correlation with many flavour compounds and after-taste descriptors and it is possible to characterize the single coffee. A system is already in place to assess the intensity of the roasting process placing it alongside a sensorial analysis. Compounds like these are true examples of “cause and effect”. They show that the variable degree of intensity of a process brings about a variation in the sensorial profile. With this in mind, a further series treatment “markers” has been established, although there is still some way to go before a definitive system can be set up due to the complexity of the “markers”. Giovanni Mastronardi, Doctoral Dissertation: Effects of Origin and Treatment of Roasting Process on the Aromatic and Sensorial Composition of Coffee. IV Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine Giovanni Mastronardi, Doctoral Dissertation: Effects of Origin and Treatment of Roasting Process on the Aromatic and Sensorial Composition of Coffee. V Tesi di dottorato di Giovanni Mastronardi, discussa presso l’Università degli Studi di Udine CONTENTS CONTENTS FIRST CHAPTER ............................................................................................. “INTRODUCTION TO GREEN COFFEE” ......................................................IX 1.1 RAW COFFEE QUALITY.........................................................................1 1.1.2 MAIN DEFECTS IN COFFEE BEANS .......................................................... 3 1.2 RAW COFFEE (ABOUT ARABICA AND ROBUSTA)...............................4 ARABICA (COFFEA ARABICA) .............................................................................. 4 ROBUSTA (COFFEA CANEPHORA) ....................................................................... 6 1.3 HARVESTING .......................................................................................11 1.3.1 THE DRY PROCESS CALLED “NATURAL COFFEE OR UNWASHED”................... 14 1.3.2 THE WET METHOD CALLED “WASHED” ....................................................... 16 1.3.2.1 Key concepts of the “wet” fermentation method .......................... 17 1.3.3 SEMI WET METHOD ................................................................................. 21 1.4 BAGGING AND STORING ....................................................................22 1.5 METHODS FOR EVALUATING THE COFFEE QUALITY (CUPPING) ....23 1.6 REFERENCES ......................................................................................25 SECOND CHAPTER ........................................................................................ “CHARACTERIZATION OF VOLATILE COMPOUNDS IN RAW ARABICA COFFEE OF DIFFERENT GEOGRAPHIC ORIGINS”....................................27 2.1 INTRODUCTION ...................................................................................28 2.2 MATERIAL AND METHODS...................................................................30 2.2.1 BIOLOGICAL MATERIAL....................................................................30