Research of Food Process Engineering

The research of the Food Structuring is aimed at creating novel scientific insights that stimulates the development of new process to make healthy food products in a more sustainable manner. Increased sustainability can be achieved through processing in a more concentrated manner, developing processes with reduced by-product stream production and the development plant-based alternatives for animal based products and ingredients.

We therefore study the effects of processing on concentrated-multicomponent materials. Main element is the understanding of deformation on those materials. For this, we developed our range of shearing devices, aimed at deforming materials in a well-defined manner at relevant processing temperature (often higher than 100 °C). Those conditions can be used to transforms blends of biopolymer into highly fibrous materials, which forms the basis for our work on meat analogues.

However, we also study the fractionation of raw materials. While mostly emphasis is on the creation of highly pure ingredients, we focus on functionality, based on the realization that hardly any food products consists of pure components only. The focus on functionality has potential to make the use of raw materials more efficient and allow the use of milder processing condition.

Finally, we develop processing concepts and frameworks for assessing, monitoring, and designing a resource efficient agri-food production system.

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. We aim 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.

Aim

Within the Food Micro Technology group, we investigate things on the micrometre (and also nanometer) scale. Based on the insights gained, we develop new technologies for the production of food products and food ingredients. You may ask yourselves why the micrometer-scale is so relevant. Well, in food, the micrometer scale is a decisive scale in structure formation (e.g. emulsions, foams, particles, or capsules), and ultimately determines the functional properties of a food product. This also holds for separation (filtration, and other innovative separation methods based on an electric switch), in which the micro/nanometer scale determines how well raw materials can be separated into functional fractions. We also use micro- and nanoparticles to design tailor-made packaging materials and foods that impact the environment less, for example as part of fully degradable films, and to give these films as well as food higher anti-oxidation properties to extend the shelf-life of foods.

Food micro-technology

Within the Food Micro Technology group, student projects mostly start with experimental observations done in our dedicated microtechnology lab, or with small-scale set-ups that are tailor-made for that purpose, and in which we can emulate conditions that are relevant for large scale processing and ideally also visualise them. In the actual production lines this would not be possible at sufficient level of detail simply because stainless steel is not transparent as would be the food products into which light can only intrude very limitedly. Furthermore, the processes that occur are very fast. In order to still be in a position to understand what is going on, we combine experimental observations at small scale, with modelling and image analysis, and reach thorough understanding of the mechanisms that play a role during e.g. structure formation of emulsions and capsules, and also investigate loss of structure e.g. due to changes in the interface composition under digestive conditions. Similarly, we approach the field of separation in which we for example study naturally occurring migration behaviour including clogging of pores, and use it to improve filtration processes (in combination with the membrane processes for food group in Twente), sometimes using an external driving force which has led to the identification of innovative separation methods.

Although we start our investigations with simplified systems on small scale, we always try to understand full complexity within food products. We both identify new raw materials (e.g., natural Pickering particles), and develop new sustainable technology. We aim to improve products, and design processes that are ultimately more sustainable and can be carried out at large scale. A special field of interest is the design of interfaces in emulsions, foams and capsules. We do that e.g., using novel protein sources or particles, and structure the interfaces in such a way that we either obtain stable products both from a physical and chemical point of view, or make the interface unstable to enable controlled release, e.g., under digestive conditions. This work is part of a long-standing collaboration with associate prof. dr. Claire Berton-Carabin who is at INRAE, Nantes.

Besides, we are interested in societal aspects that play a role when introducing new technologies. We have joint projects with the social sciences department that focus on novel foods, of which the perception is not immediately clear.

Aim

Our research on 3D food printing aims at creating ways in which we can for example personalize foods. To further advance food printing, we conduct research to better understand how food materials react to process conditions; how food composition influences printing performance; and how the printing process can be controlled to achieve high product quality using sensors. 

In collaboration with our 4TU partners, we will develop technology for sensing and feedback to autonomously adapt to the complexity of various food materials and the constant change in material properties, allowing robust food product assembly. Another important aspect of our research on additive food assembly has to do with the interaction between technology and consumers. This interaction should allow us to incorporate feedback from consumers on product quality (i.e. sensorial properties) to our product and process designs. By combining our knowledge and experiences in both engineering and food science & technology, we will make the future of personalized foods possible!

3D food printing

Examples of our 3D-printed food structures using various food materials:

• Methylcellulose
• Starch
• Pea flour dough
• Whey protein gel
• probiotics cookie
• Sodium caseinate gel

Towards adaptive extrusion-based 3D printing of complex food systems

Most studies in extrusion-based food printing focuses on the printing of single-component or binary systems at room temperature. The printing of complex food systems has however not been intensively studied. Studying the printing of complex food systems could contribute to the future development of personalized nutrition. In addition, the current system shows low adaptability to the complexity in food systems. Improving the adaptability of the extrusion system will ensure precise dosing and smooth extrusion of complex food materials, which will ultimately benefit the stability and quality of printed foods. In this first project, we aim at developing an adaptive extrusion system for the printing of complex food materials with high accuracy and quality. Different actuation methods of extrusion and complex model food systems will be investigated. Sensors will be incorporated in the extrusion system to collect data for the evaluation of extrusion performance. A data-driven model will be developed to link the output printing quality to input parameters such as printing conditions and properties of food materials. The knowledge gained in this study will help to avoid trial-and-error approaches for formulation development and process optimization in extrusion-based food printing.

Processing of concentrated and dry particulate food materials is a common operation in food industry. Think about spray drying to convert a concentrated dairy formulation into a powdered infant formula, about the use of milling and air classification to manufacture a dry-enriched pea protein concentrate, or extrusion of a paste through a nozzle during 3D food printing. While such operations are common, these often are carried out and designed based on empirical knowledge and optimized via trial and error.

In our group we therefore employ and develop experimental & modelling approaches to study and unravel underlying dynamic phenomena that play a role during processing of concentrated and dry materials. In several projects we collaborate with food industry, for whom we ultimately aim to develop mechanism-based guidelines for process optimization and new sustainable processing concepts that can be breakthroughs in terms of product quality and/or energy efficiency. Within our group we have three research lines: Dewatering and drying process, dry fractionation for making new plant-based (protein) ingredients, and 3D food printing.

Dry fractionation for making new plant-based (protein) ingredients

Dry fractionation via combination of milling and dry separation is a highly interesting technique to produce protein or fibre-enriched cereal and legume ingredients. It not only is inherently more energy efficient compared to wet fractionation processes, but it also delivers highly functional ingredients with preserved native properties. Current research is investigating amongst others new driving forces for dry separation (i.e. electrostatic separation) and combining dry fractionation with fermentation to prepare protein-enriched ingredients with enhanced nutritional value.

3D Food Printing

We investigate 3D Food Printing being a rapidly emerging technology with major promise towards making personalized foods. Although the technique suggests a simple translation from a digital food design to an attractive food product, in practice, there are many challenges ahead. Therefore, we investigate the relationship between rheology and processing of pastes by extrusion-based 3D printing. It should lead to more accurate control for 3D printing of high-quality foods. We also investigate new 3D printed food concepts that have designed component distribution such that the sensory perception can be altered. The latter approach allows making healthier foods that contain less sugar, fat or salt.

Dewatering and drying process

Dewatering and drying processes are responsible for approximately 10-15% of the total industrial energy use (80 PJ/year). In our research we adopt and develop small-scale approaches such as sessile single droplet and thin film drying to study drying processes such as spray, drum and agitated thin film drying. Experimental results are used for model development of phenomena responsible for the dynamics of product formation during drying (e.g. particle structure formation, release or degradation of specific compounds). Recently, our lab acquired a pilot-scale spray dryer / agglomerator (25 kg/h water evaporation). This spray dryer is used both for research and education purposes. 

Sustainability & efficiency analysis

Many processes use copious amounts of water, and this generates high-energy usage as well, since the foods or food ingredients need to be dehydrated (dried) again. The waste water that is produced needs to be treated, because some of the raw materials are dissolved in the waste water. These raw materials are irrevocably lost. Also other waste streams are created, because of the focus of the process design on the primary product. Therefore, only a part, and sometimes even a small part of the raw material ultimately ends up on our plate. To improve this, you first need to know where the wasteful steps are located in a process. 

For this, you can use a range of methods. We use pinch technology and exergy analysis. Pinch will tell you how to optimise the use of a particular resource. Exergy analysis will tell you how efficient you use all your resources: raw materials, water, energy, or anything else. In addition, exergy is a thermodynamic quantity that is objectively defined; therefore the results of an analysis are completely objective. The next step is to re-design a process, using the analysis. Sometimes you can cascade resources (water, energy), but sometimes you need to think about doing different things. We run research projects that concentrate on the development of the methodology for this, but most of our research projects will carry out a sustainability / efficiency analysis at some stage, and therefore this work is shared by almost all our projects.

Sustainability of Human Nutrition

We can optimise food processes to need the least possible amount of resources for the production of a food product; however we should not forget that foods are consumed and digested. In the end, we should optimise the amount of resources that we need, not for a particular food, but for our nutrition. In some cases, the way of processing directly influences the efficiency of digestion. A well-known example is the lycopene in tomatoes. Eaten raw, this lycopene is hardly digested due to its crystalline state. After investment of some exergy (see above) in a process to make a sauce out of these tomatoes, the digestion of lycopene may increase by 400%. To absorb a certain amount of lycopene, therefore, you need a lot less raw materials, albeit at the cost of some processing. 

Similarly, proteins from animal origin are highly digestible and give us all the essential amino acids. Proteins from plants are much more sustainable to produce, but they are less digestible and do not contain all essential amino acids, and their processing also requires more resources. Therefore we study the use of resources in this complete chain, from agricultural raw materials, via ingredient and food processing, preparation by the consumer, and the digestive process, to find out how to optimise this complete chain. From this, we strive to understand how to fulfil our nutritional and sensory needs in the most efficient way, with respect to all resources at the same time: raw materials, water, energy, auxiliary chemicals, etcetera.

During extraction and food processing, proteins can be modified in multiple ways. Physical modifications (for example thermal treatment) and chemical modifications (for example ingredient interactions) can not only influence each other, but also significantly affect the structural properties and functionality of proteins. Such process-induced modifications are common-place but highly complex. But once understood in detail, they represent a new possibility for the targeted functionalization of proteins during extraction or processing in food. Since every raw material differs in composition and structure, the possibilities for explorations are vast and the outcome has great potential:

Protein functionalization enhances and broadens the functionality of existing protein sources and thus their effectivity, while it can also be used to upgrade and recover proteins from waste-streams. Ultimately, this makes an important contribution to meeting the high global demand for sustainable protein sources.

Focus

Our group studies the separation principles, including the molecular interactions and molecular modifications of proteins during processing, and their consequences for the functionality of the ingredient and final food product (Figure 1). Emphasis will be on protein-protein interactions and interactions of proteins with other components (such as flavours and phenolic components), in relation to the component’s environment such as the presence of interfaces, and/or within a food matrix (emulsion, foam or gel).

The last half century, we have witnessed an enormous change in our diets, resulting in a rapid increase in diet-related diseases. In this research theme, we want to gain fundamental insights in the role of food processing and a food’s structure therein. 

We study how foods with different degree of processing/structuring are being digested and metabolized through a combination of miniaturization and simulated digestion experiments, with a special focus on structural degradation rate. Besides, we are developing purpose-designed foods and encapsulation systems to generate health effects, like appetite control and a healthy gut microbiota.