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Plant protein ingredients (isolates, concentrates) are increasingly used for food formulation due to their low environmental impact compared to animal-based proteins. A specific application is food emulsions, of which the physical and oxidative stability need to be supported. The emulsifying properties of diverse plant proteins have already been largely covered in literature, whereas only in a few studies the chemical stability of such emulsions was addressed, especially regarding lipid oxidation. In the few examples available mostly the effects caused by proteins were elaborated, whereas those caused by non-protein components have hardly been considered. Yet, plant protein ingredients are characterized by high compositional complexity, with notably a plethora of non-protein components. Topics covered in this review, therefore, include the composition of various types of plant protein ingredients (i.e., legumes, oil seeds) in relation to the fractionation processes used, and the potential effects on lipid oxidation in emulsions. The composition varies greatly among species and depends on the harvest conditions (i.e., year, location), and genetics. In addition, fractionation processes may lead to the accumulation or dilution of components, and induce chemical changes. Both protein and non-protein components can act as pro- or antioxidants contingent on their concentration and/or location in emulsions. Since the chemical composition of plant protein ingredients is often hardly reported, this makes a-priori prediction of an overall effect difficult, if not impossible. Standardizing the fractionation process and the starting material, as well as in-depth characterization of the resulting fractions, are highly recommended when aiming at rationally designing food emulsions.

Food design is often done based on a trial-and-error basis,using structure properties as an indicator of product quality.Although this has led to many good p roducts in the market, this‘cook and look’ approach could benefit from insights into dynamic processes as they occur during food formation, storage, and digestion. Currently microfluidic devices are being developed to allow these types of observations, and here we show the latest examples in the field of emulsions and foams, including effects that occur during digestion. We expect that these techniques will supply a stepping stone to thorough understanding at various length and timescales that are all instrumental in designing high-quality food products, and ultimately creating foods with health benefits.

Emulsions fortified with polyunsaturated fatty acids are highly relevant from a nutritional perspective; however, such products are prone to lipid oxidation. In the current work, this is mitigated by the use of natural antioxidants occurring in coffee.Coffee fractions with different molecular weights were extracted from roasted coffee beans. These components were positioned either at the interface or in the continuous phase of emulsions where they contributed to emulsion stability via different pathways.Coffee brew as a whole, and its high-molecular-weight fraction (HMWF), was able to form emulsions with good physical stability and excellent oxidative stability. When added post-homogenization to the continuous phase of dairy protein-stabilized emulsions, all coffee fractions were able to slow down lipid oxidation considerably without altering the physical stability of emulsions, though HMWF was more effective in retarding lipid oxidation than whole coffee brew or low-molecular-weight fraction. This is caused by various effects, such as the antioxidant properties of coffee extracts, the partitioning of components in the emulsions, and the nature of the phenolic compounds. Our research shows that coffee extracts can be used effectively as multifunctional stabilizers in dispersed systems leading to emulsion products with high chemical and physical stability.

Oil-in-water (O/W) emulsions, where oil droplets are dispersed in an aqueous phase, often experience various physical and chemical destabilization phenomena, which compromise the quality and shelf life of the final products. To achieve acceptable shelf life, emulsifiers (e.g., surfactants and animal proteins) and synthetic antioxidants (e.g., ethylenediaminetetraacetic acid and butylated hydroxyanisole) are currently used. However, over the past decade, sustainable and natural food ingredients have become preferred options. This has been a strong incentive for the present work, which has aimed at identifying the potential of biobased Maillard reaction products (MRPs) to both physically and chemically stabilize emulsions.In this thesis, we investigate the potential of MRPs, either prepared in model systems or inherently present in foods, to act as dual-function ingredients (i.e., physical stabilizers and antioxidants) in food emulsions.The first part of the thesis was designed to study the MRPs prepared in model systems: In Chapter 3, we characterized the chemical and structural features of various Maillard reaction fractions prepared from soy protein isolate (SPI) and carbohydrates (dextran or glucose). We found that the Maillard reaction progressed further with glucose than dextran, with SPI-dextran conjugates showing higher activity than SPI-glucose conjugates, and water-soluble fractions showing higher activity than insoluble fractions. Therefore, a comprehensive understanding of the physicochemical properties in each fraction could be obtained. In Chapter 4, we further assessed the ability of initial stage MRPs (SPI-dextran conjugates) to prevent lipid oxidation, when added to the continuous phase of pre-formed stock emulsions. We found that the addition of protein-based compounds increased the oxidative stability of emulsions without significantly affecting the physical stability of emulsions. Therefore, it is possible to engineer oxidatively stable emulsions b

The transition from animal- to plant-derived dietary proteins is of global importance. Plant proteins are normally processed into extracts, and due to the type of process, proteins from the globulin class are mainly extracted. Such extractions have several waste streams, containing another protein class: albumins. Here, we show that plant albumins have good functionality. We compared interfacial and foaming properties of albumins and globulins from mung bean, Bambara groundnut and yellow pea. The foaming properties of albumins were good, similar or even superior to those of whey or egg white proteins, while globulin-based foams showed low stability. Albumins form strong cohesive interfacial layers around air bubbles. Globulins are unable to create such layers, mainly due to their aggregated structures. Additionally, we provide a mild extraction method, allowing the co-extraction of albumin and globulin. This protein mixture is able to form foam with half-life times up to 450 min. Though currently underutilized, plant albumins can substitute animal proteins, especially in foaming applications, where they outcompete globulins. Their utilization could be an important contribution to the food protein transition.

Many food products contain oil-in-water (O/W) emulsions, i.e., droplets of oil in a water phase. Due to the thermodynamic incompatibility between the two liquids, the droplets need to be covered by emulsifiers to ensure physical stability. The most widely used food emulsifiers are dairy proteins which are present in e.g., beverages, infant formula or dressings. However, their production has a large impact on the environment, therefore, plant proteins are currently considered as promising alternatives. Yet, the full replacement of dairy proteins by plant proteins brings along a number of technological challenges (e.g., functionality, product taste, pre-treatments). It can therefore be advantageous to rather consider partial replacement, but the properties of dairy-plant protein blends with regard to food systems’ stabilisation had been largely unexplored. In the present work, we aimed to achieve a rational compromise between technical functionality of such blends, and product quality. We investigated formation and stability of protein blend-stabilised emulsions and focussed on the relevant interfacial phenomena. To do so, we used a multiscale approach based on characterisations at different length- and time scales. In the first chapters (Chapter 2-4), we focussed on the long term interfacial phenomena when using protein blends to formulate emulsions. We assessed the related properties of blends of pea protein isolate (PPI) with either whey protein isolate (WPI) or with sodium caseinate (SC) in Chapter 2. We showed a synergistic behaviour in terms of physical stability of the emulsions, when the blends were used. The blend-stabilised emulsions had higher surface loads compared to the individual protein-stabilised emulsions, which showed that more proteins were needed to stabilise the interface. Furthermore, compositional rearrangements at the interface were observed over days. More specifically, after emulsion formation, whey proteins were able to partly displace

A major trend in the food industry is the protein transition from animal- to plant-derived proteins. Prior to the utilisation of these ingredients, plant proteins must be extracted from the plant or crop. The most common extraction processes are extensive processes with many processing steps, requiring copious amounts of water and energy, and generating substantial amounts of waste streams. Also, this processing might alter plant protein functionality, leading to protein aggregation and lower solubility. A solution is a milder and more sustainable process, but less processing leads to protein extracts with lower protein purity due to the presence of more non-proteinaceous components, such as lipids and phenols. The aim of this thesis was to investigate the contribution of these non-proteinaceous components to the interfacial and foaming properties of mildly derived plant protein extracts. The system of interest is rapeseed, as it is high in both phenols and lipids.We performed these studies by producing a mildly derived plant protein extract and systematically mixing purified proteins with phenols or lipids. The mildly derived rapeseed protein extract was able to form stiff and viscoelastic solid-like interfacial layers, as shown by Lissajous plots in non-linear surface rheology. However, the stiffness of the interfacial films reduced at higher bulk concentrations, indicating an impact of the non-proteinaceous components. The presence of non-proteinaceous components was also shown by performing atomic force microscopy (AFM) on Langmuir-Blodgett films. The main rapeseed phenol sinapic acid was able to interact non-covalently and covalently with proteins. Covalent interaction even led to the formation of large aggregates. The protein-phenol interaction reduced the ability of the proteins to form stiff interfacial layers, leading to less stable foams.An advantage of mild purification is the extraction of intact oleosomes, which are normally disrupted in the defatting s

There is a growing interest in replacing dairy proteins with their plant-based counterparts in food emulsions. Plant proteins generally contain a substantial insoluble protein fraction, of which the properties may differ from the soluble proteins. Therefore, the use of a commercial pea protein isolate, its insoluble fraction and whey protein isolate to stabilize oil-in-water (O/W) emulsions is explored. In 100 g/kg O/W emulsions, the use of full pea protein isolate led to physically instable emulsions that showed droplet flocculation and coalescence, whereas its insoluble fraction and whey protein formed physically stable emulsions. The insoluble pea protein fraction was also able to physically stabilize high internal phase O/W emulsions (HIPEs) containing 700 g/kg oil, giving ~10 times higher viscosity than whey protein-based HIPEs. Under oxidative conditions, whey protein-stabilized emulsions showed extensive coalescence, and fast formation of lipid oxidation products. Insoluble pea protein-stabilized emulsions, showed fast lipid oxidation, but this did not affect the physical stability. In contrast, full pea proteins-based emulsions were physically instable in oxidative conditions but showed the lowest accumulation of oxidation products. These results suggest that the constituents of commercial pea protein isolate have specific functionalities, which is important knowledge for the design of stable plant protein-based emulsions.

In conventional emulsification devices, interface formation and stabilisation occur within milliseconds. Protein network formation at liquid-liquid interfaces starts at time scales similar to those of droplet formation in conventional emulsification devices (i.e., in milliseconds). Classical methods, like drop tensiometry, do not allow measurements at these time scales. Using a tailor-made microchip, we probed droplet deformation to study the interfacial rheological properties of droplets, within time scales ranging from 0.16 to 1 s. We further investigated the coalescence stability of droplets at the same time scales. Whey protein isolate (WPI), pea protein isolate (PPI), or their blends were used as emulsifiers at 0.01–1 g/L. The rheological properties of the protein-interfaces showed that early network formation takes place (<1 s). WPI-stabilised interfaces were mechanically stronger compared to PPI-stabilised interfaces, and WPI-stabilised droplets were much less prone to coalescence than their PPI counterparts. Although the blend-stabilised films showed high interconnectivity, this did not prevent droplet coalescence, probably due to structural heterogeneity. The insights obtained with the tailor-made microfluidic devices help to capture effects at short time scales and are relevant to unravel phenomena occurring in large scale processing.

Hypothesis: Many traditional or emergent emulsion products contain mixtures of proteins, resulting in complex, non-equilibrated interfacial structures. It is expected that protein displacement at oil-water interfaces depends on the sequence in which proteins are introduced during emulsion preparation,and on its initial interfacial composition.Experiments: We produced emulsions with whey, pea or a whey-pea protein blend and added extra protein post-emulsification. The surface load was measured indirectly via the continuous phase, or directly via the creamed phase. The interfacial composition was monitored over a three-day period using SDSPAGEdensitometry. We compared these findings with results obtained using an automated drop tensiometer with bulk-phase exchange to highlight the effect of sequential protein adsorption on interfacial tension and dilatational rheology.Findings: Addition of a second protein increased the surface load; especially pea proteins adsorbed to pre-adsorbed whey proteins, leading to thick interfacial layers. The addition of whey proteins to a pea

Many food products contain lipid droplets dispersed in an aqueous phase (e.g., milk, mayonnaise), thus are oil-in-water (O/W) emulsions. Food emulsions may be subjected to destabilization, both from a physical and a chemical perspective. Physical destabilization is generally prevented by the use of conventional emulsifiers such as surfactants and proteins. Chemical destabilization, in particular lipid oxidation, is a major concern in food products, especially when healthy polyunsaturated fatty acids are present, and this degradation is usually mitigated by the use of synthetic antioxidants, often in large amounts.The use of alternative ingredients for the formulation of food emulsions has been emerging, for example solid particles (so-called Pickering particles, that are very popular nowadays) that irreversibly adsorb to the interface and therewith provide high physical stability; or natural antioxidants such as tocopherols and rosemary extracts, which are attractive in the current clean-label trend to prevent lipid oxidation. The efficiency of these natural antioxidants is unfortunately often not optimal, which can be explained by their tendency to locate into the oil or water phase, whereas lipid oxidation is initiated at the oil-water interface, and thus is the place where antioxidants should be located to optimally exert their protective effect.The objective of this project was to develop food emulsions with a new and controlled architecture directed at yielding both excellent physical and oxidative stability. In these emulsions the oil droplets were covered by food-grade Pickering particles that exert a double role: they act as physical stabilizers, and as a reservoir for antioxidant molecules located close to the oil-water interface, therewith preventing the first lipid oxidation events, which is expected to drastically enhance antioxidant activity.The first part of this thesis focused on the preparation and characterization of a new food-grade lipid-based Pic

This paper starts with short descriptions of emulsion preparation methods used at large and smaller scales. We give scaling relations as they are generally used, and focus on the central role that interfacial tension plays in these relations. The actual values of the interfacial tension are far from certain given the dynamic behavior of surface-active components, and the lack of measurementmethods that can be applied to conditions as they occur during large-scale preparation. Microfluidic techniques are expected to be very instrumental in closing this gap. Reduction of interfacial tension resulting from emulsifier adsorption at the oil-water interface is a complex process that consists ofvarious steps. We discuss them here, and present methods used to probe them. Specifically, methods based on microfluidic tools are of great interest to study short droplet formation times, and also coalescence behavior of droplets. We present the newest insights in this field, which are expected to bring interfacial tension observations to a level that is of direct relevance for the large-scale preparation of emulsions, and that of other multi-phase products.

Proteins are used to stabilise oil-in-water (O/W) emulsions, and plant proteins are gaining interest as functional ingredients due to their higher sustainability potential compared to e.g., dairy proteins. However, their emulsifying properties are not that well understood, and depend on how their production process affects their physicochemical status. In the present work, we use the soluble fraction of commercial pea protein isolate to stabilise O/W emulsion droplets formed in a microfluidic device, and record coalescence stability after droplet formation (11–173 ms) for different protein concentrations (0.1–1 g/L). For the shortest adsorption times (11–65 ms) droplets were unstable, whereas for longer adsorption times differences in coalescence stability could be charted. Metal-catalysed oxidation of pea proteins performed for up to 24-h, prior to emulsion formation and analysis, increased the coalescence stability of the droplets, compared to fresh pea proteins. This may be explained by oxidation-induced protein fragmentation, leading to low molecular weight products. The Langmuir-Blodgett films looked highly heterogeneous for films prepared with fresh or mildly oxidised (3-h) proteins, and was more homogenous for 24-h oxidised proteins. This could be the cause for the observed differences in emulsion coalescence stability, structurally heterogeneous films being more prone to rupture. From this work, it is clear that the emulsifying properties of pea are strongly dependent on their chemical status, and associated structural properties at the molecular and supramolecular levels. The present microfluidic device is an efficient tool to capture such effects, at time scales that are relevant to industrial emulsification.

Recent work suggests that using blends of dairy and plant proteins could be a promising way to mitigate sustainability and functionality concerns. Many proteins form viscoelastic layers at fluid interfaces and provide physical stabilization to emulsion droplets; yet, the interfacial behavior of animal-plant protein blends is greatly underexplored. In the present work, we considered pea protein isolate (PPI) as a model legume protein, which was blended with well-studied dairy proteins (whey protein isolate (WPI) or sodium caseinate (SC)). We performed dilatational rheology at the air-water and oil-water interface using an automated drop tensiometer to chart the behavior and structure of the interfacial films, and to highlight differences between films made with either blends, or their constituting components only. The rheological response of the blend-stabilized interfaces deviated from what could be expected from averaging those of the individual proteins and depended on the proteins used; e.g. at the air-water interface, the response of the caseinate-pea protein blend was similar to that of PPI only. At the oil-water interface, the PPI and WPI-PPI interfaces gave comparable responses upon deformation and formed less elastic layers compared to the WPI-stabilized interface. Blending SC with PPI gave stronger interfacial layers compared to SC alone, but the layers were less stiff compared to the layers formed with WPI, PPI and WPI-PPI. In general, higher elastic moduli and more rigid interfacial layers were formed at the air-water interface, compared to the oil-water interface, except for PPI.

Plant protein-based foods have gained a huge interest in the past years due to environmental and health reasons. A special category of food products has been developed to mimic animal-based products using plant proteins, known as meat analogues. The technological challenge is to make a structure similar to the natural fibrous structure in meat, while still delivering food with high nutritional value. High temperature-based processes have been used to reach desirable fibrous structures, but such process conditions induce physicochemical protein modifications that can reduce functionality and protein quality. Meat provides high quality proteins and is a source of a highly bioavailable iron form. The latter motives the incorporation of this micronutrient into meat analogues. The incorporation of the most bioavailable form of iron, water-soluble iron may, however, be hampered by its prooxidant activity, which can result in lipid and protein oxidation in the final product, altering the nutritional and sensory aspects. Therefore, the encapsulation of iron is often proposed to prevent oxidation reactions in fortified food. This thesis aimed to assess and control the protein quality in plant protein-based meat analogues, as a function of the presence of soluble iron as free or encapsulated form, and of the conditions applied for the structuring process. First, two methods of encapsulation were described. The effect of iron addition was compared to the effect of processing, regarding the occurrence of protein oxidation. Then the extent of protein oxidation over each processing step from the raw plant material, to the final product, was quantified. Lipid and protein oxidation were observed in iron encapsulates, but the subsequent application of iron in meat analogues had only a marginal effect on protein oxidation compared to that of the process conditions. Furthermore, the associated physicochemical changes due to protein oxidation and processing were not detrimental to gast

Interest in supplementing food with iron to counteract dietary deficiencies has been on the rise in recent years. A major challenge is the pro‐oxidant activity of soluble iron, which compromises the chemical stability of the enriched food products. This problem could be mitigated by encapsulating iron, to physically keep it separated from oxidizable substrates, such as unsaturated fatty acids. In the present work, the physical and chemical stability of surfactant‐ or protein‐stabilized oil‐in‐water emulsions fortified with iron was investigated.

Interest has recently been rising in the development of food-compatible Pickering emulsions, i.e., particle-stabilized emulsions, and various biobased particles have been demonstrated as useful for such a purpose. Most of the related work has focused on the physical stability of the emulsions, but whether such particles can be advantageous in terms of chemical stability, and in particular, with regard to lipid oxidation, is largely unexplored. Recently, we found that colloidal lipid particles (CLPs) are efficient Pickering stabilizers, and the objective of the present study was to investigate the oxidative stability of emulsions stabilized with those particles. Three types of sunflower oil-in-water (O/W) emulsions were considered: Pickering emulsions stabilized with colloidal lipid particles (CLPs) made of high melting point (HMP) fat (tripalmitin or palm stearin), adsorbed onto the liquid oil droplets; and, as references, two conventional sodium caseinate-stabilized emulsions, of which one contained only liquid oil, and the other liquid oil mixed with HMP fat as the core of the emulsion droplets. In the presence of iron, the latter oxidized faster than conventional liquid oil and Pickering emulsions, resulting in 2- to 3-fold higher amounts of primary and secondary lipid oxidation products. This may be due to intra-droplet HMP fat pushing oxidizable lipids towards the oil-water interface, which would promote lipid oxidation. This shows that the localization of solid fat in O/W emulsions affects lipid oxidation. We also found that CLP-stabilized Pickering emulsions had similar oxidation rates as conventional sodium caseinate-stabilized emulsions containing only liquid oil. This suggests that the potential of such Pickering particles to prevent lipid oxidation is limited. This could be because diffusion of small pro-oxidant molecules is not hindered by Pickering particles, as they cannot form an interfacial barrier that is structurally homogeneous at such a small sca

My PhD project aimed at developing an edible product for non-invasive weight management, and targeted a natural feedback mechanism to induce satiety: the ileal brake. In order to trigger the ileal brake mechanism, lipids and their non-absorbed metabolites need to be sensed in the ileum. We aimed at inducing this mechanism through targeted release of lipids after oral intake, for which we developed multi-layered emulsions and emulsion-alginate beads. We showed that emulsion-alginate beads control in vitro lipolysis as a function of bead size and alginate concentration, and confirmed these findings under dynamic in vitro gastrointestinal conditions (DIDGI). Moreover, ingestion of yoghurt with emulsion-alginate beads significantly reduced food intake by 6% in overweight volunteers compared to a control group, suggesting that activation of the ileal brake was achieved. These findings have important implications for the development of weight management strategies, and understanding satiety in general.

In the quest to find approaches to prepare food grade Pickering emulsions, we studied the formation and stability to coalescence of colloidal lipid particle (CLP)-stabilized emulsions within a cross-flow microfluidic device. We show that the particles can either stabilize or destabilize the emulsions depending on the particle adsorption rate versus droplet formation rate, and on the resulting surface coverage when the droplet is formed. At low surface coverage, when droplet formation is significantly faster than adsorption, CLPs have a destabilizing effect as incomplete surface coverage leads to droplet-droplet bridging. At high surface coverage, the dense particle layer results in an effective barrier against droplet coalescence, resulting in physically stable emulsions. The observed non-monotonic dependency of emulsion droplet stability on surface coverage of CLP-stabilized emulsions is in stark contrast to what is observed for conventional surfactant-stabilized emulsions, and thus should be taken into account for the rational design of Pickering emulsions.

Delivery of lipid fractions in the lower small intestine can induce feelings of satiety, but is only possible when lipids escape the highly efficient lipolysis and adsorption in the upper gastrointestinal (GI) tract. Our objective was to gain insight in the stability of multilayered interfaces in simulated GI conditions, and their suitability for intestinal delivery of undigested lipids. Oil-in-water emulsions (d32 ∼ 5–30 μm; one- to five-layered interfaces) were produced by sequentially adsorbing biopolymers with opposite charges at pH 3.0: whey protein isolate (WPI) (cationic), pectin (anionic), chitosan (cationic). Corresponding multilayered structures were characterized using reflectometry. Influence of layer composition and thickness on its protectiveness against lipolysis of emulsions was studied in simulated GI conditions. Multilayered WPI/pectin emulsions had an improved physical stability compared to WPI-stabilized emulsions, during both storage and in vitro gastric incubation, whereas chitosan-containing emulsions were physically unstable. Reflectometry and CLSM results showed that a greater number of layers increased the adsorbed amount, forming a mesoscopically heterogeneous structure. Under simulated intestinal conditions, however, outer layers instantaneously destabilized. Accordingly, similar initial lipolysis rates were recorded for all emulsions. Yet, compared to only WPI the final extent of lipolysis was lowered by addition of a second and a third layer under mild in vitro conditions. This moderate protective effect disappeared when harsher digestive conditions were applied. From this work, it became clear why multilayered interfaces (initially built under acidic pH) can improve gastric stability of emulsions, but are prone to disintegration under intestinal conditions. This knowledge is important for designing food systems that control release of lipolytic products in targeted locations of the GI tract; the emulsions reported her

Emulsions are dispersions of one liquid in another that are commonly used in various products, and methods such as high-pressure homogenisers and colloid mills are used to form emulsions. The size and size distribution of emulsion droplets are important for the final product properties and thus need to be controlled. Rapid coalescence of droplets during emulsification increases droplet size and widens the size distribution, and therefore needs to be prevented. To increase stability of emulsions, emulsifiers are added to adsorb at the oil-water interface before droplets collide. The time allowed for emulsifier adsorption is typically in the range of sub-milliseconds to seconds and to optimise emulsification processes, emulsifier adsorption and coalescence stability need to be measured in this time-scale, for which the microfluidic methods described in this thesis were developed. Chapter 2 provides an overview of existing literature on cross-flow microfluidic emulsification. The effects of various parameters such as microfluidic design, shear forces, and interfacial tension forces on droplet formation and the resulting droplet size are discussed, as well as the use of microfluidics to produce food-grade emulsions. Based on this evaluation, the methods to elucidate interfacial tension and coalescence stability are chosen, and these are presented in the next chapters. To measure emulsifier adsorption in the sub-millisecond time-scale, a tensiometric method was developed using a cross-flow microfluidic Y-junction, which is described in Chapter 3. This method is based on the relation between droplet size and interfacial tension at the moment of droplet formation, which is referred to as the acting interfacial tension. The acting interfacial tension of a system with hexadecane as the dispersed phase and sodium dodecylsulfate (SDS, a model surfactant) solutions as the continuous phase was successfully measured for droplet formation times ranging from 0.4 to 9.4 milliseconds

The increasing prevalence of overweight and obesity requires new, effective prevention and treatment strategies. One approach to reduce energy intake is by developing novel foods with increased satiating properties, which may be accomplished by slowing down lipolysis to deliver substrates to the ileum, thereby enhancing natural gut-brain signalling pathways of satiety that are normally induced by meal intake. To develop slow release food additives, their processing in the gastrointestinal tract has to be understood; therefore, we start from a general description of the digestive system and relate that to in vitro modelling, satiety and lipolytic mechanisms. The effects of physicochemical lipid composition, encapsulation matrix and interfacial structure on lipolysis are emphasized. We give an overview of techniques and materials used, and discuss partitioning, which may be a key factor for encapsulation performance. Targeted release capsules that delay lipolysis form a real challenge because of the high efficiency of the digestive system; hardly any proof was found that intact orally ingested lipids can be released in the ileum and thereby induce satiety. We expect that this challenge could be tackled with structured o/w-emulsion-based systems that have some protection against lipase, e.g., by hindering bile salt adsorption and/or delaying lipase diffusion.