Digestion and Separation Technology

Within our group there is a strong focus on sustainable processing of foods. We define this as complete utilisation of agricultural raw materials, using a minimum of energy and water, combined with a reduction of the use of chemical processes. Enzyme technology and separation processes play a key role, since they allow waste streams to be better utilized, for example by recovering valuable components. Better understanding of food digestion is important as well, as we need to ensure that the new, more sustainable foods will be just as healthy and nutritious as the foods that they replace.

Concepts and Applications in Membrane Separation Technology

Membrane separations are important in the agro- and food industry for fractionation and concentration of various mixtures (e.g. mixtures of proteins or carbohydrates). This can be rather dilute mixtures, but nowadays more and more often it is desired to work with non-dilute mixtures with an elevated viscosity. Under concentrated conditions, interactions between the components in the mixture has to be taken into account. Mathematical modelling that includes molecular interactions, friction between molecules, viscosity and pore size distribution in the membrane is powerful to improve the accuracy of the predictions in membrane processes. This is important to improve the design of a membrane systems for non-dilute mixtures. The current focus is on the separation of proteins from a mixture. Interaction between the proteins and ions as well as the pH of the solution are critical parameters. In our lab we have a flat-sheet and spiral-wound set-up available for the experimental work.

Besides research on the separation process itself we also focus on design rules for energy efficient membrane processing for the fractionation of proteins. For membrane processes with total retention design rules are known, however, for fractionation systems, often the retentions are not complete. For these systems new design rules are needed to optimise the (energy-) efficiency of membrane processes.

Digestion of Food

We use in vitro methods to simulate the environment in the gastrointestinal tract and understand how different physiological conditions alter food breakdown and protein digestibility. Our aim is to gain a mechanistic understanding of the digestion of proteins. Ultimately we seek at assessing and improving the digestibility of protein rich foods to efficiently use the resources to produce them. A food product may have the right composition to satisfy a consumer’s need for proteins and essential amino acids to keep our body functioning properly. However, before small peptides can be absorbed and utilized, peptide bonds should become accessible for digestive proteases and peptidases. This demonstrates the importance of the composition and structure of the food matrix. Furthermore, factors such as solubility, protein structure, modifications (e.g. Maillard reaction), amino acid sequence and the presence of fibres influence digestion rate as well.

We have studied the digestion of proteins in simulated gastric environment with special attention to the role of the enzyme, pepsin. Pepsin needs to penetrate the gel microstructure and hydrolyse proteins in gel matrices. Also the pH in the stomach and the pH in the food matrix play a role in the actual activity of pepsin and therewith the degradation of the food matrix. Knowledge on the effect of pH on the kinetics of the pepsin hydrolysis and modelling of the system, combined with information on the buffering capacity of the structured proteins will give us insight in the underlying mechanisms of gastric digestion. We will apply our knowledge on pepsin and transfer it to understand the role of pancreatic enzymes such as trypsin and chymotrypsin in the degradation of pepsin-hydrolysates formed in acid (gastric) environment.

We also explore the potential applications of in silico research in which we aim at modelling digestion kinetics considering an array of conditions and ultimately optimize protein digestibility. Via collaboration with the chair groups in Human nutrition we try to bridge in vitro and in silico research with in vivo studies. Knowledge on digestion of food will learn food technologists to better design their food products, e.g. obese people might benefit from dense protein structures that are slowly digested, while food structures that are more rapidly digested are more suitable for elderly people.