The term ‘phytochemicals’ describes a bewildering number of small molecules from plants, which can be divided into many distinct classes based on their biosynthetic origin and structure. Phytochemicals include, but are not limited to, the following classes of molecules: (iso)flavonoids (e.g. flavan-3-ols and isoflavones), stilbenoids (e.g. resveratrol), lignans, (hydroxy)cinnamic acids (e.g. coumaric acid, ferulic acid), phenol-amides (e.g. avenanthramides), isothiocyanates, triterpenoid glycosides (e.g. saponins), and carotenoids. Phenolic compounds, which make up several of these classes, are the most widespread and broadly studied. Phenolics and other phytochemicals can be reactive and are prone to structural changes during plant growth, and during processing and storage of plant-derived food products or ingredients. These changes in structure also lead to changes in their properties, which can range from enhanced (bio)functionality to (undesirable) colour formation.

Description of theme

Despite the fact that phytochemicals are present in much smaller quantities in foods than carbohydrates, proteins, and lipids, they can strongly affect food properties. Phytochemical research is becoming increasingly important due to current trends in plant-based food. Our phytochemical research is focussed on three main areas.

1) Advanced phytochemical analysis: Analysis and structure elucidation of phytochemicals is at the core of our work on these compounds, as it is essential in studying phytochemical reactivity. Due to the high structural diversity of phytochemicals, their analysis can be quite challenging. We develop analytical approaches to obtain structural information on individual phytochemical molecules, as well as overall compositional data of phytochemicals present in plant-derived materials (including industrial waste streams). To this end, we employ a diverse array of advanced analytical techniques, including ultra-high performance liquid chromatography (UHPLC), high resolution mass spectrometry (HRMS), ion mobility spectrometry (IMS), and nuclear magnetic resonance (NMR) spectroscopy.

2) Oxidation of phenolic compounds: One of the most well-known examples of the oxidation of phenolic compounds is the enzymatic browning reaction that leads to formation of brown colour upon cutting or bruising of fruits. Besides undergoing enzymatic oxidation, phenolic compounds can auto-oxidise to form brown and insoluble reaction products. These oxidation reactions are often considered to be undesirable, as they negatively affect the attractiveness of foods or ingredients. On the other hand, controlled (enzymatic) oxidative coupling can also be used as a tool to modulate the structure and properties of phenolic compounds, which can lead to improved (bio)functionality.

3) Interactions of phytochemicals with other food molecules: Phytochemicals are known to interact covalently and non-covalently with various other food molecules, including proteins and metals. This is especially relevant due to the increasing popularity of plant-based foods and ingredients. For example, protein-phenolic interactions can affect sensory, technofunctional, and biofunctional properties in plant protein products. Metal-phenolic interactions can result in dark discolouration in iron-fortified food products.

The aims of the FCH theme Phytochemicals are to (i) characterize phytochemicals from various plant materials using advanced analytical techniques; (ii) monitor changes in phytochemical composition during plant growth, and during processing and storage of plant-derived food products or ingredients; (iii) modify phytochemicals with chemical, enzymatic, or microbial approaches, in order to improve their properties; and (iv) study interactions of phytochemicals with proteins and micronutrients.

Research Projects