Morphology Development and Flow Characteristics during High Moisture Extrusion of a Plant-Based Meat Analogue

Advancing molecular understanding in high moisture extrusion for plant-based meat analogs: Challenges and perspectives

In recent years, meat analogs based on plant proteins have received increasing attention. However, the process of high moisture extrusion (HME), the method for their preparation, has not been thoroughly explored, particularly in terms of elucidating the complex interactions that occur during extrusion, which remain challenging. These interactions arise from the various ingredients added during HME, including proteins, starches, edible gums, dietary fibers, lipids, and enzymes. These ingredients undergo intricate conformational changes and interactions under extreme conditions of high temperature, pressure, and shear, ultimately forming the fibrous structure of meat analogs. This review offers a overview of these ingredients and the molecular interaction changes they undergo during the extrusion process. Additionally, it delves into the major molecular interactions such as disulfide bonding, hydrogen bonding, and hydrophobic interactions, providing detailed insights into each.

Structure formation in high moisture extrudates produced from soy protein fractions varying in 7S/11S globulin ratio

Soy proteins mainly comprise 7S and 11S globulins, which have distinct structural and physical properties. To investigate the impact of soy protein composition on structure formation during high moisture extrusion (HME), fractions enriched in 7S or 11S globulins were prepared and blended in different ratios for lab-scale HME processing. Extrudates prepared from the 11S globulin-enriched fraction were inhomogeneous, as opposed to all other extrudates. Differences in extrudate structure and texture by varying the raw material protein composition were limited. However, 11S globulin-enriched fraction based extrudate was mainly stabilized by disulfide bonds, while with increasing raw material 7S globulin content the importance of non-covalent interactions increased. Even after disrupting all (non-)covalent bonds, high MW aggregates were detected in all extrudates. Thus, the protein composition of soy protein ingredients clearly impacts the type of protein-protein interactions and bonds formed during HME processing. This may hold relevance for the occurrence of specific phenomena during HME, such as syneresis, or the digestibility of the obtained products, although this requires further investigation. Overall, the findings of this study have implications for the use of protein-rich ingredients, which may vary in protein composition as the result of biological variability or prior processing, in high moisture extrusion.

Isolation and characterization of nettle (Urtica dioica L.) seed proteins: Conversion of underutilized by-products of the edible oil industry into food emulsifiers

This study aimed to upcycle a byproduct of the edible oil industry, cold-pressed nettle seed meal (CPNSM), into a plant-based emulsifier, thereby increasing the sustainability of the food system. The protein content of the nettle seed protein (NSP) powder was 48.3% with glutamic acid (16.6%), asparagine (10.7%), and arginine (9.7%) being the major amino acids. NSPs had a denaturation temperature of 66.6 °C and an isoelectric point of pH 4.3. They could be used as emulsifiers to form highly viscous coarse corn oil-in-water emulsions (10% oil, 4% NSP). Nevertheless, 10-fold diluted emulsions exhibited rapid creaming under different pH (2-9), salt (0-500 mM NaCl) and temperature (>40 °C) conditions, but they were relatively stable to aggregation. Our findings suggest that NSPs could be used as emulsifiers in highly viscous or gelled foods, like dressings, sauces, egg, cheese, or meat analogs.

Thermorheological properties and structural characteristics of soy and pumpkin seed protein blends for high-moisture meat analogs

This study explored the effects of soy protein isolate (SPI) and pumpkin seed protein concentrate (PSC) blends on the thermorheological properties and microstructure of high-moisture meat analogs. Using a Discovery Hybrid Rheometer, we observed that increasing PSC content weakened SPI network formation, resulting in decreased gel stability and a more porous, less aligned structure. Microstructural analyses (FE-SEM and FT-IR) revealed a correlation between protein network disruption and increased PSC content. Additionally, higher PSC levels reduced overall bonding (ionic, hydrogen, hydrophobic, disulfide), modifying the texture and softening the gel while retaining solid-like characteristics essential for replicating meat textures. Although full high-moisture extrusion conditions were not replicated, the observed trends offer valuable insights into texture development for meat substitutes. Future research using a closed-system rheometer is required to validate these findings and improve precision.

Unraveling the impact of thermal modulation in heating and cooling dies on the fibrous structure of high-moisture meat alternatives

We aimed to create high-moisture plant-based meat alternatives (HPMAs) that closely mimic the fibrous structure found in conventional meat. To achieve this goal, we focused on the impact of modulating the heating and cooling die temperatures during the extrusion process on the structural properties of HPMAs. The optimal temperatures for the heating and cooling dies were determined to be 160 and 50 °C, respectively, following a comprehensive analysis of various quality characteristics. These included assessments of cutting strength, texturization degree, moisture content, and microstructure. Analyzing the correlation coefficients between heating and cooling die temperatures and the quality characteristics of HPMAs revealed that modulating the cooling die temperature has a greater impact on quality characteristics than modulating the heating die temperature. The quality characteristics of HPMAs were also compared with those of boiled and sous-vide cooked chicken breasts. The optimal HPMA exhibited the most similar fibrous macro- and micro-structure to sous-vide cooked chicken breast. Consequently, our study highlights the importance of modulating the heating die and cooling die temperatures, among various process parameters of high-moisture extrusion cooking, which is crucial for producing HPMAs closely resembling conventional meat.

Cysteine, sodium metabisulfite, and glutathione enhance crosslinking between proteins during high moisture meat analog extrusion processing and may improve the fibrousness of the products

BACKGROUND

High moisture meat analog (HMMA) products processed using extrusion have become increasingly popular in the last few years. Because the formation of disulfide bonds is believed to play a critical role in the texturization mechanism, this study aimed to understand how chemical compounds capable of reducing disulfide bonds, specifically cysteine, sodium metabisulfite, and glutathione, affect the texture and the chemical interactions between the proteins.

METHOD

Wheat protein blended with cysteine, sodium metabisulfite, or glutathione at levels of 0, 0.5, 1.0, 2.5, 5.0, and 7.5 g kg-1 was extruded at three different temperatures (115, 140, and 165 °C) using a co-rotating twin-screw extruder. The feed rate (85 g min-1), the moisture content (600 g kg-1), and the screw speed (300 rpm) were kept constant. Unextruded and extruded material was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polymeric protein fractionation, and sulfhydryl group/disulfide bond analysis. Extruded samples were further analyzed for their hardness and their anisotropic index.

RESULTS

The inclusion of reductants significantly affected the structure of the obtained extrudates. Although reducing agents had a relatively small impact on the total amount of disulfide bonds, their action significantly enhanced crosslinking between the proteins. At select conditions, samples with high fibrousness were specifically obtained when cysteine or sodium metabisulfite was included at levels of 5.0 g kg-1.

DISCUSSION

In the presence of reducing agents, it is believed that disulfide bonds are split earlier during the process without binding to them, giving the protein strands more time to unravel and align, leading to a better flow behavior and more fibrous products. © 2024 Society of Chemical Industry.

Ingredient Functionality of Soy, Chickpea, and Pea Protein before and after Dry Heat Pretreatment and Low Moisture Extrusion

This study investigates the impact of dry heat pretreatment on the functionality of soy, chickpea, and pea protein ingredients for use in texturized vegetable protein (TVP) production via low moisture extrusion. The protein powders were heat-treated at temperatures ranging from 80 °C to 160 °C to modulate the extent of protein denaturation and assess their effects on RVA pasting behavior, water absorption capacity (WAC), and color attributes. The results indicate that the pretreatment temperature significantly influenced the proteins' functional properties, with an optimal temperature of 120 °C enhancing pasting properties and maintaining WAC, while a higher pretreatment temperature of 160 °C led to diminished ingredient functionality. Different protein sources exhibited distinct responses to heat pretreatment. The subsequent extrusion processing revealed significant changes in extrudate density and color, with increased density and darkness observed at higher pretreatment temperatures. This research provides insights into the interplay between protein sources, pretreatment conditions, and extrusion outcomes, highlighting the importance of controlled protein denaturation for developing high-quality, plant-based meat analogues. The findings have broad implications for the optimization of meat analogue manufacturing, with the aim of enhancing the sensory experience and sustainability of plant-based foods.

Meat analogue preparation from cricket and rice powder mixtures with controlled textural and nutritional quality by freeze alignment technique

The rising demand for sustainable protein sources has encouraged interest in alternative food products like meat analogues. This study explores formulating meat analogues using cricket powder (CP) and rice flours, comparing them with soy protein-based analogues. CP exhibited a higher soluble protein content (5.9%) than soy protein powder (4.7%), enhancing textural properties by forming fiber-like structures, increasing firmness and adhesion, and reducing chewiness. Despite having a lower water holding capacity (WHC) than soy analogues, all samples outperformed chicken breast WHC. Under freezing conditions, CP and rice flour combinations formed multilayered structures in protein gels. The optimal formulations were CP and sticky rice flour (ratio 6:1) with respect to their texture properties, fiber structure, and nutritional value. This study highlights the potential of cricket powder and rice flour combinations as viable meat analogue ingredients, addressing the need for sustainable protein sources in the food industry.

Alien introgression to wheat for food security: functional and nutritional quality for novel products under climate change

Crop yield and quality has increased globally during recent decades due to plant breeding, resulting in improved food security. However, climate change and shifts in human dietary habits and preferences display novel pressure on crop production to deliver enough quantity and quality to secure food for future generations. This review paper describes the current state-of-the-art and presents innovative approaches related to alien introgressions into wheat, focusing on aspects related to quality, functional characteristics, nutritional attributes, and development of novel food products. The benefits and opportunities that the novel and traditional plant breeding methods contribute to using alien germplasm in plant breeding are also discussed. In principle, gene introgressions from rye have been the most widely utilized alien gene source for wheat. Furthermore, the incorporation of novel resistance genes toward diseases and pests have been the most transferred type of genes into the wheat genome. The incorporation of novel resistance genes toward diseases and pests into the wheat genome is important in breeding for increased food security. Alien introgressions to wheat from e.g. rye and Aegilops spp. have also contributed to improved nutritional and functional quality. Recent studies have shown that introgressions to wheat of genes from chromosome 3 in rye have an impact on both yield, nutritional and functional quality, and quality stability during drought treatment, another character of high importance for food security under climate change scenarios. Additionally, the introgression of alien genes into wheat has the potential to improve the nutritional profiles of future food products, by contributing higher minerals levels or lower levels of anti-nutritional compounds into e.g., plant-based products substituting animal-based food alternatives. To conclude, the present review paper highlights great opportunities and shows a few examples of how food security and functional-nutritional quality in traditional and novel wheat products can be improved by the use of genes from alien sources, such as rye and other relatives to wheat. Novel and upcoming plant breeding methods such as genome-wide association studies, gene editing, genomic selection and speed breeding, have the potential to complement traditional technologies to keep pace with climate change and consumer eating habits.

High-Moisture Extrusion of Plant Proteins: Fundamentals of Texturization and Applications

The growing demand for sustainable and healthy food alternatives has led to a significant increase in interest in plant-based protein products. Among the various techniques used in creating meat analogs, high-moisture extrusion (HME) stands out as a promising technology for developing plant-based protein products that possess desirable texture and mouthfeel. During the extrusion process, plant proteins undergo a state transition, causing their rheological properties to change, thereby influencing the quality of the final extrudates. This review aims to delve into the fundamental aspects of texturizing plant proteins using HME, with a specific focus on the rheological behavior exhibited by these proteins throughout the process. Additionally, the review explores the future of HME from the perspective of novel raw materials and technologies. In summary, the objective of this review is to provide a comprehensive understanding of the potential of HME technology in the development of sustainable and nutritious plant-based protein products.

Next-Generation Plant-Based Foods: Challenges and Opportunities

Owing to environmental, ethical, health, and safety concerns, there has been considerable interest in replacing traditional animal-sourced foods like meat, seafood, egg, and dairy products with next-generation plant-based analogs that accurately mimic their properties. Numerous plant-based foods have already been successfully introduced to the market, but there are still several challenges that must be overcome before they are adopted by more consumers. In this article, we review the current status of the science behind the development of next-generation plant-based foods and highlight areas where further research is needed to improve their quality, increase their variety, and reduce their cost, including improving ingredient performance, developing innovative processing methods, establishing structure-function relationships, and improving nutritional profiles.

Near-infrared spectroscopy to quantify overall thermal process intensity during high-moisture extrusion of soy protein concentrate

High-moisture extrusion (HME) is widely used to produce meat analogues. During HME the plant-based materials experience thermal and mechanical stresses. It is complicated to separate their effects on the final products because these effects are interrelated. In this study we hypothesize that the intensity of the thermal treatment can explain a large part of the physicochemical changes that occur during extrusion. For this reason, near-infrared (NIR) spectroscopy was used as a novel method to quantify the thermal process intensity during HME. High-temperature shear cell (HTSC) processing was used to create a partial least squares (PLS) regression curve for processing temperature under controlled processing conditions (root mean standard error of cross-validation (RMSECV) = 4.00 °C, coefficient of determination of cross-validation (R2CV) = 0.97). This PLS regression model was then applied to HME extrudates produced at different screw speeds (200-1200 rpm) and barrel temperatures (100-160 °C) with two different screw profiles to calculate the equivalent shear cell temperature as a measure for thermal process intensity. This equivalent shear cell temperature reflects the effects of changes in local temperature conditions, residence time and thermal stresses. Furthermore, it can be related to the degree of texturization of the extrudates. This information can be used to gain new insights into the effect of various process parameters during HME on the thermal process intensity and extrudate quality.

Structural and mechanical anisotropy in plant-based meat analogues

The rising demand for plant-based meat analogues as alternatives to animal products has sparked interest in understanding the complex interplay between their structural and mechanical properties. The ability to manipulate the processing parameters and protein blend composition offers fundamental insights into the texturization process and holds economic and sustainable implications for the food industry. Consequently, the correlation between mechanical and structural properties in meat analogues is crucial for achieving consumer satisfaction and successful market penetration, providing comprehensive insights into the textural properties of meat analogues and their potential to mimic traditional animal produce. Our study delves into the relationship between structural and mechanical anisotropy in meat analogues produced using high moisture extrusion cooking, which involves blending protein, water, and other ingredients, followed by a controlled heating and cooling process to achieve a fibrous texture akin to traditional meat. By employing techniques such as scanning small-angle X-ray scattering, scanning electron microscopy, and mechanical testing we investigate the fibrous structure and its impact on the final texture of meat analogues. We show that textural and structural anisotropy is reflected on the mechanical properties measured using tensile and dynamic mechanical techniques. It is demonstrated that the calculated anisotropy indexes, a measure for the degree of textural and structural anisotropy, increase with increasing protein content. Our findings have significant implications for the understanding and development of plant-based meat analogues with structures that can be tuned to closely resemble the animal meat textures of choice, thereby enabling consumers to transition to more sustainable dietary choices while preserving familiar eating habits.

Influence of Lowering the pH Value on the Generation of Fibrous Structures of Protein Gels with Different Network Types

High-moisture extrusion of plant proteins to create meat-like structures is a process that has met with increasing attention in the recent past. In the process, the proteins are thermomechanically stressed in the screw section of the extruder, and the resulting protein gel is structured in the attached cooling die. Various protein sources, notably soy protein isolate (SPI) and wheat gluten, are used to form gels with different networks: SPI creates a physical, non-covalent network, while gluten forms a chemical, covalent one. The food industry frequently adds weak acids to modify taste and shelf life. However, it is known that a change in pH affects the gelation behavior of proteins because the repulsive forces within and between the proteins change. The research reported here was carried out to investigate for the two proteins mentioned the influence of pH modification by the addition of citric acid and acetic acid on gel formation and the meat-like structures produced. For this purpose, materials and parameters were screened using a closed cavity rheometer, followed by extrusion trials at pH 7.36-4.14 for SPI and pH 5.83-3.37 for gluten. The resulting extrudates were analyzed optically and mechanically, and protein solubility was tested in a reducing buffer. For both protein systems, the addition of acid results in less pronounced meat-like structures. At decreasing pH, the complex viscosity of SPI increases (from 11,970 Pa·s to 40,480 Pa·s at 100 °C), the generated gel becomes stronger (strain decreased from 0.62 to 0.48 at 4.5 × 105 Pa), and the cross-linking density grows. For gluten, a decreasing pH results in altered reaction kinetics, a more deformable resulting gel (strain increased from 0.7 to 0.95 at 4.5 × 105 Pa), and a decreased cross-linking density. Solubility tests show that no additional covalent bonds are formed with SPI. With gluten, however, the polymerization reaction is inhibited, and fewer disulfide bonds are formed.

The interaction between wheat and pea protein influences the final chemical and sensory characteristics of extruded high moisture meat analogs

Plant-based meat analog products, including those produced by extrusion processing, have become increasingly popular. Complete comprehension of the texturization mechanism and the formation of fibrousness would help improve existing products and extend the variety of plant sources used. Therefore, this study aimed to provide improved insight into the mechanism of texturization during the processing of high-moisture meat analog (HMMA) products. Blends with different wheat and pea protein ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wheat:pea) were extruded at a screw speed of 400 rpm, two different moisture contents (50% and 55%), and a feed rate of 90 g/min using a co-rotating twin-screw extruder. Extrudates were analyzed for their texture, free sulfhydryl groups, disulfide bonds, and solubility in different extractants relative to the raw ingredient blends. In addition, a sensory analysis was conducted using the rapid and cost-effective "rate-all-that-apply" (RATA) methodology. The interplay between the two protein types had synergistic effects on the system parameters torque, pressure, and specific mechanical energy, as well as on some textural and sensory parameters. Molecular analyses were not influenced by the interplay between wheat and pea protein as the molecular analyses followed linear trends with the pea inclusion level. Analysis of protein solubility suggests that the texturization mechanism differs slightly depending on the protein type. It is suggested that the texturization of wheat protein depends highly on disulfide bonds, whereas the texturization of pea protein relies on the combination of disulfide bonds and non-covalent interactions. Additionally, RATA was found to be a valuable tool for HMMA products.

Effect of Process Variables and Ingredients on Controlled Protein Network Creation in High-Moisture Plant-Based Meat Alternatives

The market has observed a rapid increase in the demand for plant-based foods as an alternative to animal meat products. Technologies such as high-moisture extrusion (HME) have the potential to develop anisotropic structures using alternative protein ingredients. This article discusses the different possible mechanisms responsible for structure formation and the effect of extrusion process parameters and outlines the recent advances in the long cooling dies (LCDs) used for meat alternative development. The role of different protein ingredients and the impact of combining them with other biopolymers were also evaluated. The underlying mechanism behind anisotropic structure formation during HME is a synergistic effect, with substantial dependence on the source of ingredients and their processing background. Formulation including proteins derived from plants, insects, animals, and microalgae with other biopolymers could pave the way to develop structured meat alternatives and fill nutritional interstices. Dynamic or rotating annular gap cooling dies operating at freely controllable shear and static annular gap dies are recent developments and assist to produce layered or fibrous structures. The complex chemical sites created during the HME of plant protein favour flavour and colour retention. This paper summarises the recent information published in the scientific literature and patents, which could further help researchers to fill the present knowledge gaps.

High moisture extrusion of plant proteins: advances, challenges, and opportunities

High moisture extrusion is a widely used technology for producing fibrous meat analogues in an efficient and scalable manner. Extrusion of soy, wheat gluten, and pea is well-documented and related products are already available in the market. There has been growing interest to diversify the protein sources used for meat analogues due to concerns over food waste, monocropping and allergenicity. Optimizing the extrusion process for plant proteins (e.g., hemp, mung bean, fava bean) tends to be time consuming and relies on the operators' intuition and experience to control the process well. Simulating the extrusion process has been challenging so far due to the diverse inputs and configurations involved during extrusion. This review details the mechanism for fibrous structure formation and provides an overview of the extrusion parameters used for texturizing a broad range of plant protein sources. Referring to these data reduces the resources needed for optimizing the extrusion process for novel proteins and may be useful for future extrusion modeling efforts. The review also highlights potential challenges and opportunities for extruding plant proteins, which may help to accelerate the development and commercialization of related products.

Rheological properties of dry-fractionated mung bean protein and structural, textural, and rheological evaluation of meat analogues produced by high-moisture extrusion cooking

A closed cavity rheometer was used to study the rheology of dry-fractionated mung bean protein -DFMB- (55% protein d.m.). Then, the high-moisture extrusion cooking at 40% and 50% moisture contents and different temperatures (115, 125, 135 and 145 °C) was performed, investigating the impact on structural, textural, and rheological properties of extrudates. When subjected to a temperature ramp (40-170 °C), DFMB showed an increase of G* from 70 °C, as a consequence of starch gelatinization and protein gelation. The peak, indicating the end of aggregation reactions, was at 105 °C and 110 °C for DFMB at 50% and 40% moisture content, respectively. The time sweep analysis described the protein behavior in no-shear/shear conditions, highlighting a more pronounced effect of the temperatures compared to moisture content. During the extrusion cooking, the temperature increase led to a decrease of pressure, indicating a reduction of the melt viscosity. The microstructure of the extrudates showed a more pronounced anisotropic profile when higher temperatures were applied. Hardness, chewiness, and cohesion were directly correlated with the temperature, which also affected the rheological properties of extrudates. A combination of textural and rheological analyses can offer a clear overview of the structural characteristics of meat analogues.

Rework Potential of Soy and Pea Protein Isolates in High-Moisture Extrusion

High-moisture extrusion (HME) is an effective process to make fibrous products that can be used as meat analogues. In this study, the effect of extrusion of already extruded products (i.e., re-extrusion) was tested with the aim to explore the potential of rework in HME. The rework of material is important because it is a route to reduce waste, which is always produced, for example during the start or at the end of a production run. Pea and soy protein isolates (PPI and SPI) were first extruded, then freeze-dried and ground, and extruded again. The visual and textural properties of the fibrous products were evaluated. Also, the rheological properties, solubility, and water-holding capacity (WHC) of the ingredients and the products after the first and second extrusion were quantified. The obtained freeze-dried powders after the first HME cycle had a reduction in solubility of 15% for PPI and 74% for SPI. Furthermore, WHC was reduced by 65% and 17% for PPI and SPI, respectively. After the second HME cycle, the reduction in solubility and WHC was augmented to 22% and 90% for PPI, and 79% and 63% for SPI. No effect on stock and loss moduli after heating and cooling were found, even after two HME cycles. SPI fibrous products did not differ in cutting strength, anisotropy index, or visual appearance after re-extrusion. Only, a decrease in hardness was detected, from 62.0 N to 51.1 N. For PPI, re-extrusion did reduce the cutting force and hardness but not the anisotropy index. It was concluded that even though HME induces a loss of solubility and WHC, this did not affect the fibrous texture formation of the protein. This means that the texture formed during HME does not depend on the process history and that rework is thus possible for fibrous products.

Effects of Process Parameters on the Fibrous Structure and Textural Properties of Calcium Caseinate Extrudates

Textured calcium caseinate extrudates are considered promising candidates in producing fish substitutes. This study aimed to evaluate how the moisture content, extrusion temperature, screw speed, and cooling die unit temperature of the high-moisture extrusion process affect the structural and textural properties of calcium caseinate extrudates. With an increase in moisture content from 60% to 70%, there was a decrease in the cutting strength, hardness, and chewiness of the extrudate. Meanwhile, the fibrous degree increased considerably from 1.02 to 1.64. The hardness, springiness, and chewiness showed a downward trend with the rise in extrusion temperature from 50 °C to 90 °C, which contributed to the reduction in air bubbles in the extrudate. Screw speed showed a minor effect on fibrous structure and textural properties. A low temperature (30 °C) in all cooling die units led to damaged structure without mechanical anisotropy, which resulted from fast solidification. These results show that the fibrous structure and textural properties of calcium caseinate extrudates can be effectively manipulated by adjusting the moisture content, extrusion temperature, and cooling die unit temperature.

The development process of plant-based meat alternatives: raw material formulations and processing strategies

With the rapid growth of the world's population, the demand for meat is gradually increasing. The emergence and development of plant-based meat alternatives (PBMs) offer a good alternative to solve the environmental problems and disease problems caused by the over-consumption of meat products. Soybean is now the primary material for the production of PBMs due to its excellent gelation properties, potential from fibrous structure, balanced nutritional value, and relatively low price. Extrusion is the most widely used process for producing PBMs, and it has a remarkable effect on simulating the fibrous structure of real meat products. However, interactions related to phase transitions in protein molecules or fibrous structures during extrusion remain a challenge. Currently, PBMs do not meet people's demand for realistic meat in terms of texture, taste, and flavor. Therefore, the objectives of this review are to explore how to improve fiber structure formation in terms of raw material formulation and processing technology. Factors to improve the taste and texture of PBMs are summarized in terms of optimizing process parameters, changing the composition of raw materials, and enriching taste and flavor. It will provide a theoretical basis for the future development of PBMs.

XRT for visualizing microstructure of extruded meat replacers

X-Ray Tomography (XRT) was used to visualize the microstructure of extruded meat replacers. The high moisture extrudates contained lamella, that became visible upon pulling the extrudate apart. In frozen state, these lamella could be visualized with XRT. The freezing increased the density difference between the water-rich and protein-rich layers, thus increasing the contrast obtained in the XRT. Differences in the physical structure were reflected in the measured structure. In non-frozen samples, no lamella were visible, indicating insufficient contrast. Because of the contrast obtained in frozen samples, we conclude that the XRT technique is a valuable addition to investigate extrudate structure, that can be used to quantify differences in extrudates obtained by for example variation in composition. Here we showed a higher lamella thickness for soy protein isolate (SPI) compared to more fibre-rich soy protein samples.

Hemp: A Sustainable Plant with High Industrial Value in Food Processing

In the era of SDGs, useful plants which provide valuable industrial outputs and at the same time pose less impact on the environment should be explored. Hemp seems one of the most relevant gluten-free crop plants to meet such requirements. Its high nutritional value is comparable to soy. Moreover, almost the whole body of the hemp plant has a wide array of utility: industrial production of food, fiber, and construction materials. In view of environmental sustainability, hemp requires less pesticides or water in cultivation compared to cotton, a representative fiber plant. This short review investigates hemp's sustainability as a plant as well as its utility value as a highly nutritional material in the food industry. Recent application research of hemp protein in food processing includes plant milk, emulsifiers, fortification of gluten-free bread, plant-based meat production, as well as membrane formation. These studies have revealed distinctive properties of hemp protein, especially in relation to disulfide (S-S)/sulfhydryl (-SH)-mediated interactions with protein from other sources. While its cultivation area and industrial use were limited for a while over confusion with marijuana, the market for industrial hemp is growing rapidly because it has been highly reevaluated in multiple areas of industry. Conclusively, with its sustainability as a plant as well as its distinctive useful property of the seed protein, hemp has promising value in the development of new foods.

Production of Fish Analogues from Plant Proteins: Potential Strategies, Challenges, and Outlook

Fish products are consumed by human beings as a high-quality protein source. However, overfishing, and pollution puts out an urgent call to seek a new strategy to substitute fish protein for secure eco-sustainability. Plant-based fish analogs, which mimic the structure, texture, and flavor of fish meat products, are a rapid-growing segment of the food products. The purpose of this review is to discuss the feasibility and potential strategies for developing plant-based fish analog. The nutritional properties, especially the protein quality of plant-based fish analogs, were discussed. Furthermore, a thorough comparison was made between fish and terrestrial animal muscle structures, including both macroscopical and microscopical structures. Potential processing technologies for producing plant-based fish analogs from plant proteins and approaches for the characterization of the fish analog structures were elaborated. Comparing all the current processing techniques, extrusion is the predominately used technique in the current industry. At the same time, 3D-printing and electrospinning have shown the prominent potential of mimicking fish muscle structure as bottom-up approaches. Finally, key challenges and future research were discussed for the potential commercialization of plant-based fish analogues. The primary focus of this review covers the innovative works that were indexed in the Web of Science Core Collection in the past five years.

Plant-Based Meat Alternatives: Technological, Nutritional, Environmental, Market, and Social Challenges and Opportunities

There is a growing awareness that fostering the transition toward plant-based diets with reduced meat consumption levels is essential to alleviating the detrimental impacts of the food system on the planet and to improving human health and animal welfare. The reduction in average meat intake may be reached via many possible ways, one possibility being the increased consumption of plant-based meat alternatives (PBMAs). For this reason, in recent years, hundreds of products have been launched on the market with sensory attributes (i.e., taste, texture, appearance, and smell) similar to their animal counterparts; however, these products have often a long list of ingredients and their nutritional values are very different from animal meat. The present review aims to highlight the main opportunities and challenges related to the production and consumption of PBMAs through an interdisciplinary approach. Aspects related to the production technology, nutritional profiles, potential impacts on health and the environment, and the current market and consumer acceptance of PBMAs are discussed. Focusing on the growing literature on this topic, this review will also highlight research gaps related to PBMAs that should be considered in the future, possibly through the collaboration of different stakeholders that can support the transition toward sustainable plant-based diets.

High moisture extrusion cooking of meat analogs: A review of mechanisms of protein texturization

High-moisture extrusion cooking (HMEC) is an efficient method for converting proteins and polysaccharides into fibrous structure that is used in the industrial production of meat analogs. The purpose of this review is to systematically evaluate current knowledge regarding the modification of protein structure including denaturation and reassembly upon extrusion processing and to correlate this understanding to the structure of the final products. Although there is no consensus on the relative importance of a certain type of bond on extrudates' structure, literature suggests that, regardless of moisture level, these linkages and interactions give rise to distinctive hierarchical order. Both noncovalent and disulfide bonds contribute to the extrudates' fibrous structure. At high water levels, hydrogen and disulfide bonds play a dominant role in extrudates' texture. The process parameters including cooking temperature, screw speed, and moisture content have significant albeit different levels of impact on the texturization process. Their correlation with the ingredients' physiochemical properties provides a greater insight into the process-structure-function relationship of meat analogs. The tendency of protein and polysaccharide blends to phase separate rather than produce a homogeneous mix is a particularly important aspect that leads to the formation of fibrous layers when extruded. This review shows that systematic studies are required to measure and explain synergistic and competitive interactions between proteins and other ingredients such as carbohydrates with a focus on their incompatibility. The wide range of plant protein source can be utilized in the HMEC process to produce texturized products, including meat analogs.

Plant-Based Meat Analogues from Alternative Protein: A Systematic Literature Review

This study aimed to conduct a systematic literature review (SLR) of the research performed in the plant-based meat analogues area. Historical, current, and future tendencies are discussed. The paper offers a comprehensive SLR coupled with a bibliometric analysis of the publication from 1972 to January 2022. The articles were obtained using a research string and precise inclusion and exclusion criteria from two prominent databases, Scopus and Web of Science (WoS). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow technique was used to describe the data screening and selection. In total, 84 publications were selected for further analysis after a thorough literature assessment. From this study, six main themes were identified: (1) objectives of the study; (2) type of plant protein; (3) product type; (4) added ingredients; (5) texturization technique; and (6) quality assessment considered in the studies. Recent trends in publication imply that meat analogue technology is gaining prominence. This review revealed significant research on improving meat analogues via texturization. Even though extrusion is used industrially, the technique is still in its infancy and needs improvement. Future studies should focus more on fiber and protein-protein interactions, macromolecule conformation and mechanisms, diversifying or improving current methods, sensory attributes, and gastrointestinal absorption rate of each novel protein ingredient.

The effect of psyllium (Plantago ovata Forsk) fibres on the mechanical and physicochemical characteristics of plant-based sausages

Psyllium is a source of natural dietary fibre with recognised health benefits that can be used as a hydrocolloid with functional food applications. The purpose of this study was to determine the effect of different levels of Plantago ovata fibres in plant-based sausages on their composition, physicochemical, and mechanical properties. Proximate composition was studied. Water activity (aw), water release, pH, colour measurement, texture profile analysis (TPA), and Warner-Bratzler Shear Force (WBSF) were determined to establish the physicochemical and textural properties of sausages. A plant-based sausages microstructure study and a sensory study were carried out to better understand conformation and to determine their acceptance. The results showed that sausages had high ash and carbohydrate contents but, above all, a low-fat content. The use of psyllium increased water-holding capacity. The results also indicated that employing Plantago ovata white (PW) fibre can minimise mechanical problems and reduce colour changes. However, PW fibre showed less retained water, which was why chickpea starch further developed and was more gelatinised. At the same time, the plant-based sausages with PW fibre obtained the best overall score with the fewest colour changes in the sensory evaluation. Nevertheless, further studies are recommended to improve the texture and acceptability of these plant-based sausages.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00217-022-04063-2.