BSC THESIS FOOD TECHNOLOGY Chairgroup Food Quality and Design, WUR Supervisors Vincenzo Fogliano and Xandra Bakker-de Haan September 2016 – May 2017 S. A. Pijnenburg THE IMPACT OF SPECIES, 940819675120 ROASTING AND FERMENTATION ON MELANOIDIN CONTENT AND ANTIOXIDANT CAPACITY IN PROCESSED THEOBROMA BEANS Abstract The aim of this thesis is to investigate the impact of Theobroma species, fermentation and roasting degree on melanoidin content and antioxidant capacity of Theobroma beans. Beans of T. bicolor, T. grandiflorum and T. cacao were investigated. It was assumed that the water-soluble >20 kiloDalton fraction of the roasted beans consisted nearly purely of water-soluble melanoidins. A higher melanoidin content was found in unfermented cacao than in fermented cacao. A higher melanoidin content was found in mildly roasted cacao than in heavily roasted cacao. Likewise, the antioxidant capacity of melanoidins from unfermented cacao was higher than of melanoidins from fermented cacao. The antioxidant capacity of melanoidins from mildly roasted cacao was higher than the antioxidant capacity of melanoidins from heavily roasted cacao. Mildly roasted unfermented cacao had the highest melanoidin content and antioxidant capacity. With respect to the bicolor and grandiflorum samples, it was found that the estimated total melanoidin content was higher than of the compared cacao samples. However, due to bicolor and grandiflorum’s greater water holding capacity, the melanoidin yield was lower than that of the compared cacao samples. Acknowledgements Many people at FQD and in my personal life helped me with this thesis, through explanations or moral support. I can’t thank all of them, so hereby; if you talked to me at any point while I was writing this thesis, I probably talked to you about it (I talk a lot). Thank you for listening. Special thanks to Xandra and Vincenzo; they listened to me talking about cacao and ‘weird beans’ more than anyone else and still managed to see my crazy ideas as creativity and me making things difficult for myself as interesting. Thank you for your support and your patience. And of course; thank you Jonathan, for the company and fun in the last leg of this thesis! I hope you enjoy your cacao melanoidin trip down the rabbit hole as much as I did. 1 Contents 1. Introduction ......................................................................................................................................... 4 1.1 The Theobromae family ..................................................................................................... 4 1.1.1 Cacao ............................................................................................................................. 4 1.1.2 Bicolor ............................................................................................................................ 5 1.1.3 Grandiflorum .................................................................................................................... 5 1.2 Melanoidins ...................................................................................................................... 6 1.3 Cacao processing and melanoidin formation .......................................................................... 7 1.4 Research aim ................................................................................................................... 9 2. Materials and methods ..................................................................................................................... 10 2.1 Experimental design ......................................................................................................... 10 2.2 Statistical analysis ........................................................................................................... 10 2.3 Materials ........................................................................................................................ 11 2.3.1 Theobroma beans ............................................................................................................ 11 2.2.2 Chemicals ....................................................................................................................... 11 2.4 Methods ......................................................................................................................... 12 2.4.1 Sample preparation .......................................................................................................... 12 2.4.2 Roasting ......................................................................................................................... 12 2.4.3 Defatting ........................................................................................................................ 14 2.4.4 Extraction ....................................................................................................................... 16 2.4.5 Ultrafiltration ................................................................................................................... 17 2.4.6 Antioxidant capacity ......................................................................................................... 17 3. Results ............................................................................................................................................... 19 3.1 Roasting ......................................................................................................................... 19 3.2 Sample characterisation .................................................................................................... 20 3.2.1 Overview of sample characteristics ..................................................................................... 20 3.2.2 Colour ............................................................................................................................ 21 3.2.3 Foaming capacity ............................................................................................................. 21 3.2.4 pH versus melanoidin content ............................................................................................ 21 3.3 Bean composition ............................................................................................................ 21 3.3.1 Bean composition ............................................................................................................ 21 3.3.2 Melanoidin content of bean components .............................................................................. 22 3.3.3 Antioxidant capacity of bean components ............................................................................ 23 3.4 Effects of Theobroma species, fermentation and roasting degree ............................................. 28 3.4.1 Effect of species and roasting degree .................................................................................. 28 3.4.2 Effect of fermentation and roasting degree .......................................................................... 30 3.4.3 Effect of roasting degree overall ......................................................................................... 31 4. Discussion .......................................................................................................................................... 32 4.1 Measuring error versus found effects/ Reliability ................................................................... 32 4.2 Noise factors/ Variability ................................................................................................... 32 2 4.2.1 Reproducibility earlier research .......................................................................................... 32 4.2.2 Bean origin ..................................................................................................................... 32 4.2.3 Roasting degree .............................................................................................................. 32 4.3 Unexpected results .......................................................................................................... 33 4.3.1 Low melanoidin yield ........................................................................................................ 33 4.3.2 Possible contamination of melanoidin fraction....................................................................... 33 5. Conclusion ......................................................................................................................................... 35 5.1 Sample characterisation .................................................................................................... 35 5.2 Impact of Theobroma species, fermentation and roasting degree on melanoidin yield and antioxidant capacity ............................................................................................................... 35 5.2.1 Species .......................................................................................................................... 35 5.2.2 Fermentation .................................................................................................................. 35 5.2.3 Roasting degree .............................................................................................................. 35 5.2.4 Highest melanoidin content and antioxidant capacity ............................................................. 35 5.2.5 In summary; answers to section 1.4 Research aim ............................................................... 36 5.3 Recommendations