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The development of plant-based meat analogues is an important aspect of the transition towards using more plant proteins. Production of such products with texture (and rheology) adequate for consumer acceptance like meats is a great challenge. However, there is a current lack in quantitative methods to compare whole cut meats and plant-based analogues that also consider its fibrous structures. We tackled this problem by combining non-linear shear rheology and shear-induced normal stress measurements on whole cut meats (beef and chicken) and plant-based fibrous model systems for meat analogues (soy and pea protein isolates combined with wheat gluten). We found different response in the linear viscoelastic regime for different samples, and the non-linear viscoelastic regime provided a deeper understanding into the role of structural components. Meat samples showed rearrangements at small strains and lower energy dissipation, higher intracycle strain stiffening, and a larger normal stress response at large strains than plant-based fibrous products, due to more elastic fibers. The plant-based fibrous products behave more solid-like until a larger strain, but the fibrous structures break down at large deformations resulting in higher energy dissipation, and show a lower normal stress response than meat. We therefore explore the importance of fiber properties and orientation on the nonlinear rheology of fibrous model systems for meat analogues, and provide a robust methodology to quantitatively compare different mechanical responses of meat and plant-based fibrous meat analogues. These results thereby allow comparison and tuning mechanical responses of plant-based meat analogue products towards real meat.

In this article, we study the phase behavior of two polydisperse hydrocolloids: dextran and polyethylene oxide. We combine the data on the experimental osmometric virial coefficients of the pure components with the experimental critical point of their aqueous mixture and the size distribution of each component from a previously published study in order to predict the phase boundary, spinodal, and fractionation upon demixing of the polydisperse mixture. We compare the results of our calculation to the experimental phase diagram. Our method reveals a better correspondence with the experimental binary phase behavior than modeling each component as monodisperse. The polydispersity of the hydrocolloids causes the phase separation boundary to shift to lower concentrations and the miscibility region to decrease and change its shape from a rotated U-shape to a W-shape.

We study the liquid phase behavior of ternary mixtures of monodisperse hard spheres in solution. The interactions are modeled in terms of the second virial coefficient and can be additive hard sphere (HS) or non-additive hard sphere (NAHS) interactions. We give the set of equations that defines the phase diagram for mixtures of three components. We calculate the theoretical liquid–liquid phase separation boundary for two-phase separation (the binodal) and, if applicable, the three-phase boundary, as well as the plait points and the spinodal. The sizes of the three components are fixed. The first component (A) is the smallest one, the second component (B) is four times the size of the smallest component, and the third (C) component is three times the size of the smallest one. The interaction between the first two components is fixed, and this AB sub-mixture shows phase separation. The interactions of component C with the other two components are varied. Component C can be compatible or incompatible with components A and B. Depending on the compatibility of the components, the phase diagram is altered. The addition of the third component has an influence on the phase boundary, plait points, stability region, fractionation, and volume ratio between the different phases. When all sub-mixtures (AB, AC, and BC) show phase separation, a three-phase system becomes possible when the incompatibility among all components is high enough. The position and size of the three-phase region is dependent on the interactions between the different sub-mixtures. We study the fractionation off all components depending on specific parent concentrations.

One of the most important fluid dynamics challenges is to understand and model the flow behavior of liquids under complex boundary conditions. How fluids behave in the vicinity of a solid or another fluid surface can significantly influence their flow profile. In particular, spreading of liquids on different substrate can be greatly affected by boundary conditions and the interactions of the fluid with the neighbouring surfaces. In general, the parameter space in the spreading problem is very broad and in each case based on the boundary conditions and the relevant time scale of the system a particular set of parameters should be taken into account. Many of these parameters are coupled and cannot be addressed separately.In this thesis, we employ a unique configuration of “a droplet on a soap film” to study the spreading behaviour of complex liquids. In this set-up since the droplet is suspended in the air and the contact area between the droplet and the soap film is very limited, the spreading behaviour of liquids can be studied in the absence of a solid or deep liquid boundary. We started our journey with this ambition to understand and model the governing dynamics of spreading of liquids under this boundary condition and even calibrate this set-up as a method to study the spreading behaviour for thin film formation of complex liquids. With 4 experimental chapters presented in this thesis, we succeeded to understand and model the role of some of the major governing  parameters.In Chapter 2 we studied how the surface tension gradient between the droplet and soap film governs the spreading. Additionally, we investigated the effect of droplet volume and the size of the soap film. In Chapter 3 we took a close look at the effect of surfactant-surfactant interactions on the spreading behavior of droplets on the soap film. In the next step, we studied the spreading behavior of more complex liquids consisting a mixture of polymer and surfactants in Chapter 4. For low c

The ability to separate enzymes, or cells or viruses, from a mixture is important and can be realized by the incorporation of the mixture into a macromolecular solution. This incorporation may lead to a spontaneous phase separation, with one phase containing the majority of one of the speciesof interest. Inspired by this phenomenon, we studied the theoretical phase behavior of a model system composed of an asymmetric binary mixture of hard spheres, of which the smaller component was monodisperse and the larger component was polydisperse. The interactions were modeled in terms of the second virial coefficient and could be additive hard sphere (HS) or nonadditive hard sphere (NAHS) interactions. The polydisperse component was subdivided into two subcomponents and had an average size ten or three times the size of the monodisperse component. We gave the set of equations that defined the phase diagram for mixtures with more than two components in a solvent.We calculated the theoretical liquid–liquid phase separation boundary for the two-phase separation (the binodal) and three-phase separation, the plait point, and the spinodal. We varied the distribution of the polydisperse component in skewness and polydispersity, and we varied the nonadditivity between the subcomponents as well as between the main components. We compared the phase behavior of the polydisperse mixtures with binary monodisperse mixtures for the same average size and binary monodisperse mixtures for the same effective interaction. We found that when the compatibility between the polydisperse subcomponents decreased, the three-phase separation becamepossible. The shape and position of the phase boundary was dependent on the nonadditivity between the subcomponents as well as their size distribution. We conclude that it is the phase enriched in the polydisperse component that demixes into an additional phase when the incompatibility between the subcomponents increases.

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.

Hypothesis: Tuning and controlling the flow behavior of multi-component liquids has been a long-lasting struggle in various technological applications. Here, we studied Marangoni spreading of a polymer-surfactant ternary solution when deposited on a soap film with higher surface tension. The spreading front becomes unstable into a fingering pattern above the entanglement concentration of the polymer solution, indicating that the interplay between the elastic and interfacial properties drives the instability. Balancing these terms results in a critical length scale for the onset of the instability. Experiments To investigate the connection between the rheological characteristics of the samples and the origins of the instabilities, various rheological tests were performed. Elastic and loss modulus of the samples were measured within the linear viscoelastic regime. The spreading behavior of the solutions was studied using high-speed imaging techniques. Findings At low concentrations of polymers, spreading dynamics are governed by surface tension gradient and viscous dissipation leading to a stable front growing linearly in time. However, above the entanglement concentration of polymers spreading front destabilizes into a daisy shape pattern suggesting the elastic forces dominating the spreading dynamics. We introduced a length scale that precisely predicts the onset of the instability.

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

For sustainability reasons, there is an ongoing shift from animal- to plant-based proteins, which is often referred to as the protein transition. The research of this PhD thesis was conducted in the context of that protein transition. The PhD thesis describes the effect of mild aqueous fractionation processes on the functionality of pea protein, in terms of molecular and microstructural characteristics. The thesis is structured according to the type of model foods studied.The first part focusses on pea protein dispersions and gels. The first step in a protein fractionation process is milling of the seed. The morphology of the pea seed before and after milling was visualized using electron microscopy. Subsequently, alkaline extraction and isoelectric precipitation was applied to obtain five pea protein fractions exposed to different extents of processing and with different compositions. It was found that extensively fractionated pea proteins had a substantial thickening capacity in dispersion. This physical behaviour was attributed to the ability of pea protein to form aggregates with a high specific volume. Furthermore, pea proteins were able to form homogeneous coacervate dispersions at certain pH and salt conditions, given that the proteins were only mildly fractionated. Upon heating, mildly fractionated pea protein fractions were able to form stiff and ductile gels, while more extensive fractionation resulted in pea fractions that formed soft and brittle gels. The first part of this thesis shows that with mild fractionation specific pea protein functionalities are preserved.The second part of this thesis reports on the stabilization of oil and air after incorporation in foams, emulsions and emulsion-filled gels. Fractionation could be used to induce a separation between pea albumins and globulins, and it was found that albumins showed good foaming properties, while globulins were better emulsifiers. The foaming properties were related to the interfacial rheology

Protein aggregation into gel networks is of immense importance in diverse areas from food science to medical research; however, it remains a grand challenge as the underlying molecular interactions are complex, difficult to access experimentally, and to model computationally. Early stages of gelation often involve protein aggregation into protein clusters that later on aggregate into a gel network. Recently synthesized protein microparticles allow direct control of these early stages of aggregation, decoupling them from the subsequent gelation stages. Here, by following the gelation of protein microparticles directly at the particle scale, we elucidate in detail the emergence of a percolating structure and the onset of rigidity as measured by microrheology. We find that the largest particle cluster, correlation length, and degree of polymerization all diverge with power laws, while the particles bind irreversibly indicating a nonequilibrium percolation process, in agreement with recent results on weakly attractive colloids. Concomitantly, the elastic modulus increases in a power-law fashion as determined by microrheology. These results give a consistent microscopic picture of the emergence of rigidity in a nonequilibrium percolation process that likely underlies the gelation in many more systems such as proteins, and other strongly interacting structures originating from (bio)molecules.

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.

The Arctic region is projected to experience amplified warming as well as strongly increasing precipitation rates. Equally important to trends in the mean climate are changes in interannual variability, but changes in precipitation fluctuations are highly uncertain and the associated processes are unknown. Here, we use various state-of-the-art global climate model simulations to show that interannual variability of Arctic precipitation will likely increase markedly (up to 40% over the 21st century), especially in summer. This can be attributed to increased poleward atmospheric moisture transport variability associated with enhanced moisture content, possibly modulated by atmospheric dynamics. Because both the means and variability of Arctic precipitation will increase, years/seasons with excessive precipitation will occur more often, as will the associated impacts., Astrodynamics & Space Missions

Food oral processing refers to the oral manipulations of food upon ingestion (i.e. oral behavior), the production of a bolus safe to swallow and simultaneously the sensory responses evoked from the structural transformation of the bolus. Deeper understanding of the factors involved in oral processing can facilitate the creations of food products that are goal-specific (e.g. controlling eating rate) and population-specific (e.g. elderly consumers) besides being nutritive and palatable. The main factors determining oral processing are the consumer and food being eaten. Therefore, in this thesis both factors were explored and their contribution to oral behavior, bolus properties and sensory perception determined. Chapter 2 explored whether or not consumers exhibit different oral behaviors for a specific food product and how these differences in behavior might impact sensory perception. The results confirmed that consumers used different oral behaviors which differed in consumption time. Vigorous protocols (chewing and natural style) required shorter consumption time than passive protocols (melting). Furthermore, changes in oral behavior also influence dynamic sensory perception. For instance, changing oral behavior influenced significantly aroma and taste attributes, where upon applying an active oral behavior aroma attributes were detected earlier and for longer time than when a passive protocol was applied. On the other hand, if a passive protocol was applied, taste perception was perceived earlier and for longer time whereas aroma perception was delayed. Additionally, this chapter highlighted the existence of attribute chronology during oral processing and that consumers adopt an oral processing behavior that is optimized in terms of oral efficiency and sensory perception.Chapter 3 explored a broad range of commercial foods and the effect of their rheological and mechanical properties on oral behavior parameters. The results showed that consumers adapted their

In this thesis we aimed to get a better understanding of the phase behavior of polydisperse and multi-component mixtures in solution. We approached this in a systematic way, starting with model systems of hard spheres and ending with a system of polydisperse macromolecules.In Chapter 1 we presented a short overview of the available literature on polydisperse en multi-component mixtures that show segregative phase separation.In Chapter 2 we reviewed the theory of interactions in systems of a solute component in a solvent based on the second virial coefficient. The theory was expanded to allow for multiple distinguishable types of solute components. This chapter describes the general equations used in the thesis that define the phase boundary, stability of the mixture, and critical point. Next to the theory, the chapter also dealt with the effect of polydispersity on the phase behavior of a binary mixture of additive hard spheres. This chapter showed that the largest species in the polydisperse component had the largest influence on the changes in the phase diagram.In Chapter 3 we deal with the effect of non-additivity on the phase behavior of a binary mixture of hard spheres with slight polydispersity or impurities. Non-additivity between the two polydisperse and monodisperse component shifts the phase boundary to higher (negative non-additivity) or lower (positive non-additivity) concentrations. Negative non-additivity within a polydisperse component decreased overall compatibility and lowered the phase boundary. Positive non-additivity within a polydisperse component pushed the two-phase boundary to slightly higher concentrations and made three-phase demixing possible.In Chapter 4 we discussed the influence of a third component added to a binary mixture that is incompatible. When the third component is compatible with both binary components, the phase boundary is not altered and upon demixing, the third component is present in both phase in similar amounts as in th

The prediction of phase separation is essential to understand and control the properties of food systems. In this work, an existing theoretical model for describing phase separation between binary mixtures of hydrocolloids, using a virial approach up to second order, is extended with several new analytical expressions. These new expressions allow one to determine the three virial coefficients directly from three characteristics of the phase diagram, where the critical point plays a pivotal role and allows one to predict the complete phase diagram. The advantage of this approach is that experimental techniques, like membrane osmometry or static light scattering, to directly measure virial coefficients can be, in principle, avoided. It was found that just the location of the critical point is sufficient to determine two of the three virial coefficients, when one of the virial coefficients is known. When, in addition to the critical point, one other characteristic of the phase diagram is known with sufficient accuracy, like the slope of the tie-lines near or far away from the critical point, all three virial coefficients can be determined from the phase diagram. Using this approach, three virial coefficients for aqueous mixtures of dextran and polyethylene oxide were determined and compared to the ones obtained from membrane osmometry.

Background and aim: Many foods consumed daily are composed of multiple elements which often display a heterogeneous structure, flavour, and appearance. These heterogeneous food products are generally well-liked by consumers, although little information is available about the key factors responsible for their appreciation. This thesis aims to determine how food and consumer characteristics affect sensory perception and liking of heterogeneous foods by engineering structural heterogeneities at different length scales. The effects of structural heterogeneity on expected and perceived sensory properties and liking of foods were investigated considering different consumer groups.Methods: A combination of model and real food products were used to establish the effect of physical and physicochemical properties of heterogeneous food matrices on sensory perception and liking in relation to consumer expectations and physiological characteristics. Instrumental characterization of the products was related to the sensory perception, studied through a variety of methods (e.g. R.A.T.A., Ideal Profile, TDS). Consumer groups differing in age (i.e. healthy young adults vs. healthy elderly) or nationality/ethnicity (i.e. Dutch, Caucasian vs Chinese, Asian) were used to explore the generalisability of the effects.Results and conclusions: This thesis showed that variations in mechanical properties (e.g. fracture stress) between the components are the main driver of perceived heterogeneity by the consumer. For particle-filled foods, oral perception of the product can be influenced by varying both the size and the hardness of added particles, independently from the matrix consistency. Visual recognition of particle as a function of type, size, and concentration can stir expected sensory profile and liking of familiar and novel food products, although the palatability of the food depends on the particle properties. It was demonstrated that consumers prefer the presence of soft and easy-to

Nowadays there is a growing interest in exploiting new sources of plant proteins as functional ingredients in food products. In recent years, Bambara groundnut (Vigna subterranea (L.) Verdc.) [BGN] has been explored as such a potential plant protein source, as a means of value-addition to this leguminous crop. To elucidate on the macroscopic functionality of BGN protein isolates, the focus of our study was on the extraction and characterisation of the vicilin protein fraction as the known major storage protein present in legume seeds. BGN vicilin had a high protein content (91%) and formed the largest component in relation to the other protein fractions. Together with molecular weight profiles obtained with gel electrophoresis and size-exclusion chromatography coupled with light scattering, the purity of vicilin and its presence as the predominant protein fraction in BGN black-eye seeds were confirmed. The isoelectric point (pH 5.3), solubility profile (highest solubility 86% at NaCl concentrations above 200 mM) and thermal denaturation temperature (92 °C) of BGN vicilin correspond to the range reported for other legume vicilins. Furthermore, the gelation behaviour of BGN vicilin gels was investigated using dynamic oscillatory measurements. These data were further analysed with scaling models, which revealed that fractal scaling was best suited for description of the BGN vicilin gel networks. The gel microstructures were visualised with confocal laser scanning and scanning electron microscopy.

Hydrogel microbeads are capable of trapping, protecting and delivering components. We investigated how different production parameters influenced the microstructure of protein and polysaccharide hydrogel microbeads, and how that in turn influenced the functional properties of the microbeads as encapsulation devices in various systems. We found that by changing the production method and the hydrocolloid type and density we could create a variety of structures with different strengths, breakdown patterns and diffusivity profiles. Most importantly, the functionality of the hydrogel microbeads is not dependent on the individual production parameters, but on a system in which the hydrogel matrix, the diffusing compound moving into or out of the microbead, and the environment in which the microbead is present, all play varying but important roles in the complete system. The hydrogel microbead by itself is a viable encapsulation device but may also be the basis for a more complex encapsulation system in which several components may be encapsulated together and which may be triggered to release by outside influences.