On the Prediction of Polyphenol Properties Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de rector magnificus prof. ir. K.Ch.A.M. Luyben voorzitter van het college voor promoties, in het openbaar te verdedigen op Dinsdag 30de 2015 om 12:30 uur door David MÉNDEZ SEVILLANO Chemical Engineer geboren te San Andrés del Rabanedo, Spanje Dit proefschrift is goedgekeurd door de promotor: Prof. dr. ir. L.A.M. van der Wielen Copromotor: Dr. Ir. M. Ottens Samenstelling promotiecommissie: Rector Magnificus voorzitter Prof. dr. ir. L.A.M. van der Wielen Technische Universiteit Delft, promotor Dr. Ir. M. Ottens Technische Universiteit Delft, copromotor Independent members: Prof.dr.ir. C.G.P.H. Schroen Wageningen University of Research Prof.dr.ir. M.C. Kroon Technische Universiteit Eindhoven Prof.dr. G.J. Witkamp Technische Universiteit Delft Dr. A. Krijgsman Unilever Prof.dr.ir. H.J. Noorman Technische Universiteit Delft, reservelid The research described in this thesis was performed at the Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, the Netherlands. The research was financially supported by the Institute for Sustainable Process Technology (ISPT) in the project FO-10-03. Cover: Diego García “It is change, continuing change, inevitable change, that is the dominant factor in society today. No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be.... This, in turn, means that our statesmen, our businessmen, our everyman must take on a science fictional way of thinking.” -Isaac Asimov- Table of Contents Chapter 1: 7 Introduction Chapter 2: 27 Model comparison for the prediction of Green Tea Catechins Solubility in ethanol/water mixtures Chapter 3: 57 MPP-UNIFAC, A Predictive Activity Coefficient Model for Polyphenols Chapter 4: 81 Resin Selection for the Separation of Caffeine from Green Tea Catechins Chapter 5: 101 Mechanism of Isoflavone Adsorption from Okara extracts onto Food-Grade Resins Chapter 6: 127 A Thermodynamic Lattice Model Describing Adsorption of Phytochemicals onto Macroporous Polymeric Resins Chapter 7: 149 Outlook Summary/Samenvatting 151 Curriculum Vitae 159 Publications and Conferences 161 Acknowledgements/Dankwoord 163 5 6 Chapter 1: Introduction 1.1.Background and Motivation Food materials contain many useful compounds that either get discarded during processing or not entirely exploited. The generated waste is around 38% of the original material for fruits or 57% in the case of meat in the United States1 and up to 97% of this waste is usually discarded or used as landfill2. Currently there are several initiatives to use this waste as starting material for other processes3 like, for example, the production of bio-hydrogen.4 This food waste still contains many high-value compounds such as proteins, vitamins or polyphenols. Some of these compounds show favourable health properties which classifies them as nutraceuticals. A very interesting family of nutraceuticals are the flavonoids because of their antioxidant properties. Flavonoids are present in small concentrations in the food matrix. The key to their purification is to bring them into solution and treat them via different unit operations until the required purity and composition is met. The design of the purification process, or processes in general, may be aided by mechanistic mathematical models5. Process modelling in Chemical Engineering, Biotechnology or Food Processing is a combination of mass balances, energy balances, mass transfer and equilibrium models. Some of these models are required in a specific step of the process (like isotherm models in chromatography) and some of them are required throughout the process (like solubility giving the maximum concentration). The use of these models decreases dramatically the time and money put into a process design by doing process optimization in-silico, which allows to optimize the 7 yield and productivity by considering all possible scenarios and not only the ones that can be deduced from prior experience. In this work, we apply state of the art models to predict and describe the behaviour of flavonoids in different steps of the process validating them against experimentally determined properties. Furthermore, when the experiments show a different behaviour than the one predicted by the models, we develop new models to capture this behaviour and statistically analyse its validity. We limit the study to equilibrium models since good predictions can be made for kinetic phenomena based on existing models and correlations, but prediction of equilibrium phenomena is less developed for these molecules. Below an overview of the molecules this thesis deals with, as well as the models describing equilibrium properties will be introduced. 1.2. Flavonoids 1.2.1. Definition Flavonoids are a large group of phytochemicals that are formed by two phenyl rings joined by a 3-carbon chain (Figure 1). In most cases, that chain is bound through an oxygen to the first phenyl ring (ring A in Figure 1). Figure 1: Typical backbone of a flavonoid molecule 8 Flavonoids are derived from phenylalanine in plant cells6 which is used for the production of p-coumarate, a direct precursor of the flavonoids. Each of the flavonoid-producing plants has a different pathway that decorates the flavonoid with different functionalized groups that can vary from a hydroxyl group to a sugar moiety. A large number of flavonoids have been discovered in a large variety of plants such as tea, soy, berries, grapes, etc. These flavonoids have been associated to the beneficial properties that the ingestion of these plants can give and many studies are being conducted to obtain a better understanding of the influence of said flavonoids on human health7-11. Besides in-vivo studies on human population many studies in vitro12 and in different types of animals13 are being published as well with new evidence on the beneficial properties of these compounds. 1.2.2. Types As previously stated, different functional groups define the different flavonoids. However, in some cases the differences are in the backbone (i.e. a ketone group in C4 of Figure 1) and based on those changes, the flavonoids are separated into different subgroups: 1.2.2.1.Major flavonoids. They are the biggest subgroup. Their main molecular difference from other groups is that the ring B (Figure 1) is bound to the carbon 2 and this carbon is bound to the ring A through an ether bond. This subgroup consists of several families (Figure 2) that differ mainly on the ring C. Well-known polyphenols can be found amongst these families such as kaempferol, quercetin (flavonols), luteolin, apigenin (flavones), hesperidin, naringin (flavanones), the catechins (flavanols), delphinidin and pelargonidin (as part of the anthocyanins). 9 Figure 2: Different types of major flavonoids 1.2.2.2. Isoflavonoids: The polyphenols in this subgroup differ from others in the binding between rings B and C (Figure 1). In this case, the ring B is bound to ring C in carbon 3, instead of carbon 2 like the major flavonoids. Isoflavones are part of the so-called “pythoestrogens”,14 plant chemicals that can cause estrogenic effects due to their similarity with 17-β-estradiol (also in Figure 3). This subgroup consists of three families being isoflavones the most important of them with polyphenols like genistein or daidzein. Pumilanol (isoflavanols) or glyasperin F (isoflavanones) are other flavonoids that belong to this subgroup. 10