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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.

High moisture extrusion (HME) is a common method to produce meat analogues. This process requires cooling of the product in the die and is associated with a high mechanical energy input. Here, we use high-temperature shear cell (HTSC) technology to better understand the importance of cooling while shearing for the formation of fibrous products upon thermomechanical processing. The maximal rotational speed for fibrous structure formation from a pea protein isolate-wheat gluten (PPI-WG) blend was found to be the same (

Rapeseed and sunflower seeds are broadly used for oil production, while the co-products of rapeseed and sunflower meal after the oil extraction are mainly applied as animal feed. With high protein content and rich nutritional given the amino acid composition, rapeseed and sunflower cake/meal are considered as a potential plant protein source for foods as well. Therefore, the aim of this work was to enable the use of the co-product of rapeseed meal and de-oiled sunflower meal kernel for meat analogue application through creating new scientific insights in the fractionation process and the structuring potential of resulting ingredients. This thesis addressed a research question whether complete removal of phenolic compounds from de-oiled sunflower kernel is necessaryIn chapter 2, rapeseed protein concentrate and isolate (RPC and RPI) were fractionated from rapeseed meals, and their functional properties were compared. The RPC was obtained by aqueous ethanol washing and consisted of 62% protein (DM) and 28% polysaccharides (DM). The washing process removed almost all the phenolic compounds and oil. The RPI was fractionated with alkaline extraction, ultrafiltration, and dialysis. It contained 94% protein (DM), but still contained a considerable amount of phenolic compounds (3.6% DM) after fractionation. The protein in RPC was completely denatured and had a low protein solubility, whereas the protein in RPI was still native and highly soluble. RPC particles were found to be sand-like when dispersed in water. Nevertheless, a concentrated RPC dispersion (40 wt% DM) leads to a much higher complex modulus (G*) by the temperature sweep using a closed cavity rheometer compared to the RPI dispersion.The high complex modulus (G*) of the RPC dispersion suggested its potential for use as an ingredient in meat analogues (Chapter 3). The structuring properties of RPC were studied with two recipes: RPC-only and RPC-wheat gluten (WG) mixture of 40 wt% DM in the shear cell. It was foun

3D food printing is an emerging technology that allows building of 3D food structures by layer-by-layer deposition following a digital design. Hitherto, most research related to 3D food printing focused on exploration of suitable recipes and optimal printing parameters for making custom-shaped 3D-printed foods, such as chocolates, cookies, cheese and vegetable pastes. Although the previous studies broadened the scope of 3D food printing applications, they did not provide rational guidelines to replace trial-and-error strategies during optimization of new 3D food printing applications by considering rheological properties of food materials suitable for printing. Moreover, most efforts focused on customization of the food design whereas 3D printing also had been suggested to allow preparation of foods with altered perceived taste and texture. The few studies that showed the impact of 3D printed food design on texture properties did primarily employ instrumental analysis while these should be complemented with sensory texture and mouthfeel perception. This study therefore aimed at understanding the relationships between material properties, printing conditions and physical properties of printed foods (Chapter 2 and 3), and how 3D food printing can be used to affect texture and taste perception of foods through modulating food structure (Chapter 4, 5 and 6).&nbsp

Consumption of plant-based meat analogues offers a way to reduce the environmental footprint of the human diet. High-moisture extrusion cooking (HMEC) and shear cell processing both rely on thermo-mechanical treatment of proteins to product fibrous meat-like products. However, the mechanisms underlying these processes are not well understood. In this review we discuss the effect of thermo-mechanical processing on the physicochemical properties and phase behavior of proteins and protein mixtures. The HMEC and shear cell processes are comparable in their basic unit operations, which are (1) mixing and hydration, (2) thermo-mechanical treatment, and (3) cooling. An often overlooked part of the extruder that could be crucial to fibrillation is the so-called breaker plate, which is situated between the barrel and die sections. We found a lack of consensus on the effect of heat on protein-protein interactions, and that the experimental tools to study protein-protein interactions are limited. The different mechanisms for structure formation proposed in literature all consider the deformation and alignment of the melt. However, the mechanisms differ in their underlying assumptions. Further investigation using novel and dedicated tools is required to fully understand these thermo-mechanical processes.

Proteins used for meat analogues are at this moment mostly derived from dairy, soy and wheat gluten. Pea protein is considered to be a promising alternative, because of its lower allergenic potential, good functionality and lower environmental impact. The scientific goal of this work was therefore is to gain in-depth understanding in the structure formation process of plant-based proteins and to connect those to the functional properties of pea proteins. To do so, pea protein isolate (PPI) and blends of PPI with other components that are relevant for next generation meat analogues were processed in the shear cell, characterised using nonlinear (large deformation) rheological measurements and benchmarked to meat, commercial meat analogues and products based on soy protein isolate (SPI). It was concluded that a common requirement of the fibrous structures that can be obtained by using blends with gluten, is the ability to form a bi-continuous network. The research in this thesis showed the importance of elastic properties of both components in the blend. Heating at high temperature induces elasticity in the proteins during structuring, but the extent of this effect depended on the actual protein source. The mechanical and rheological benchmarking against real meat indicate that the plant-based materials have similar textural properties as chicken, but that their elasticity is not yet the same and therefore an important parameter for future research to the creation of good-quality meat analogues.

The market for plant-based alternatives for meat products is growing for about a decade now (Ismail et al., 2020). Initially, traditional soy-foods were consumed for thousands of years, and still remain popular in Eastern diets nowadays also as alternative to meat. More recent though, the versatile properties, health benefits and relatively low price of soy has made it a source for the production of protein ingredients, which in their turn have stimulated the innovation of soy-based products, especially meat analogues, for broad markets (Thrane et al., 2017). As a results, novel soy-foods are mainly developed based in the use of soy protein ingredients, but the current forms of commercially available soy protein ingredients are not optimized for these products. Specifically, current fractionation processes of soy protein focuses on achieving high protein purity, or specific protein functionality to fit broad applications as functional ingredients at low addition levels. Unfortunately, resource- and energy-intensive processing steps are involved in the process of making soy protein ingredients. Therefore, it was deemed important to investigate more effective fractionation pathways to produce functional soy protein ingredients aimed at use as bulk ingredient in novel food applications such as meat analogue.The current aqueous fractionation process of soy protein includes sequential oil extraction, alkaline solubilization, acid precipitation and intensive washing steps to remove oil, insoluble carbohydrate and soluble carbohydrate in the soybean, respectively. This process leads to ingredients with a protein content over 85%. The oil extraction and intensive washing steps require the use of organic solvent (such as hexane) and large amount water respectively, which is undesired from an environmental point of view for soy fractionation. Therefore, we explored the effects of simplification of current process by omitting these steps. The majority of oil was successfully r

The sustainability of the human diet could be improved by lowering meat consumption and offering consumers plant-based meat substitutes as an alternative. Consumers are thought to prefer meat substitutes with a high similarity to real meat. Therefore, meat analogues that accurately mimic the different textural properties of real meat are being developed. Recent advancements in high-moisture extrusion cooking and shear cell processing have enabled the production of fibrous, meat-like products from plant-based ingredients. This has resulted in a wider research scope, which includes other textural properties such as the juiciness. For meat, the juiciness is associated with the water holding capacity (WHC). We have aimed to better understand the uptake, distribution, and release of water of meat analogues. Since these properties relate to the water holding capacity (WHC), this work could help the development of juicier meat analogues.Meat analogues were simplified to gels consisting of two protein phases, such as soy protein isolate (SPI) and gluten. In Chapter 2 we studied the WHC of two-phase gels with different ratio's between SPI and gluten. The WHC of single-phase SPI gels as a function of applied pressure could be described adequately with Flory-Rehner theory. The WHC of gluten gels was very low and could not be described with Flory-Rehner theory as the WHC did not depend on the applied pressure. Therefore, the WHC of gluten was approximated as a constant when describing the WHC of the two-phase gels. The WHC of SPI gels was found to depend on the polymer content at gelation. This was accounted for by determining the water partitioning before gelation using Flory-Rehner theory. The WHC of SPI in the two-phase gels decreased as gluten content increased. This was explained as the result of a mechanical interaction by which the continuous gluten network lowers the WHC of the entrapped SPI phase. In Chapter 3 the effect of gluten on the WHC was further studied using p

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

The development of next-generation meat analogues can be accelerated by in-depth knowledge of the rheological properties of dense biopolymer blends. Blends comprising plant proteins such as pea protein isolate or soy protein isolate combined with wheat gluten can be used to create a wide range of structures. The objective of this study is to demonstrate the use of texture maps to systematically show the rheological properties of plant proteins under conditions relevant to processing of meat analogue products. The first texture map was constructed by plotting the stress and strain at the end of the linear viscoelastic regime of the strain sweeps and a second map was based on the stress and strain at the crossover point of those sweeps. Next, a colour scheme was used to visualize the relative importance of the viscous and elastic contributions as a function of the strain amplitude and different ratios of each protein in the blend. The maps and schemes showed that heating induced elasticity. In pea protein–wheat gluten blends, lower strain, stress and elasticity values were obtained for pea compared with wheat gluten. In soy protein–wheat gluten blends, the texture properties were almost similar for the two components. Soy protein–wheat gluten blends are tougher and more elastic than pea protein–wheat gluten blends.

Inverting the balance of animal versus plant protein in our consumption pattern is needed to keep producing foods sustainably. Since the turn of the century, novel technologies have been developed that allow development and production of next generation meat analogues. Protein structuring using the shear cell has provided a route to mimic whole cut meat, while innovative industrial research has resulted in the development of a plant-based heme ingredient that provides a taste and cooking experience that is similar to comminuted beef products. In addition, crop processing technologies to produce protein concentrates and enriched fractions are paving the way to a more sustainable protein supply. Clever blending of plant proteins improves meat analogue structure, and it potentially improves the protein nutritional quality score. In combination, these technologies give us the opportunity to meet supply and consumer demand for attractive plant-based products. At the same time, a couple of challenges remain; however, these are expected to be solved in the near future.

Mixed gels of plant proteins are being investigated for use as meat analogues. Juiciness is an important characteristic for the acceptability of meat analogues. The juiciness is assumed to be governed by the hydration properties, or water holding capacity, of the gel (WHC). We analysed the WHC of single-phase gels of respectively soy protein and gluten by applying Flory-Rehner theory. This enabled us to describe the WHC of more the complex mixed gels. The WHC of mixed soy protein - gluten gels is shown not to be a linear combination of their constituents. At high volume fractions, soy forms a continuous network and swells similarly to pure soy without being hindered by gluten. However, increasing gluten content leads to a gradual decrease in soy swelling. This is due to the mechanical interaction between soy and gluten. We propose that gluten-rich gels have a continuous gluten network that entraps soy and hinders its swelling. The elastic moduli of the gluten network were extracted from WHC data, and are in reasonable agreement with experimentally determined moduli. A better understanding of the effect of mixed gel composition on WHC is valuable for the development of the next generation meat analogues.

Concentrated calcium caseinate dispersions can be transformed into hierarchically fibrous materials using shear deformation. The resulting material is relevant for its structural resemblance to meat, which has a potential to be a basis of new meat analogue products. Thus, calcium caseinate can be used as a model system for studying fibrous structure formation. Overall, the research established that fibrous structure formation under well-defined shear flow is enhanced by air bubbles. In case of spray-dried calcium caseinate, the high anisotropy is caused by a combination of the anisotropy in the protein phase and the additional effect of air. The effect of air is a result of air bubble alignment with air bubbles remaining mostly spherical. However, the presence of largely elongated air bubbles in an isotropic matrix could still induced fibrous appearance and mechanical anisotropy when using roller-dried calcium caseinate.

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

The overall aim of this thesis is to enhance the potential use of oilseed ingredients from underutilised sources, here the sunflower press cake, for food applications. The thesis emphasises on the interactions among the ingredients present in sunflower seeds and cake (proteins and phenols). Although these interactions are the main reason behind the underutilisation of sunflower cake, in this research we showcase their beneficial potential and argue against the removal of the phenols during protein extraction. The recommended processing concept directs the focus towards less enriched multicomponent mixtures. It concludes that high purity of sunflower proteins is not a prerequisite for good functional properties meaning that utilisation of mixtures of ingredients, obtained when using mild conditions, is not only possible but also promising.

Calcium caseinate dispersions can be transformed into anisotropic, fibrous materials using the concept of shear-induced structuring. The aim of this study is to further investigate the relative importance of air bubbles and protein on the mechanical anisotropy of calcium caseinate material. In this study, the effect of air on mechanical anisotropy of these fibrous materials was described with a load-bearing model, with the void fraction, and the bubble length and width as input parameters. The anisotropy of the protein phase was estimated using materials obtained from deaerated dispersions after shearing at different shear rates. We concluded that the deformation of air bubbles can only partly explain the mechanical anisotropy; the anisotropy of the protein phase is more important. Based on all results, we further concluded that the anisotropy of the protein phase was affected by the air bubbles present during the structuring process. This effect was explained by locally higher shear rate in the protein matrix during the structuring process.