High Moisture Extrusion Research Articles

Effects of wheat gluten-soy protein ratios and moisture levels on high-moisture extruded meat analogues for burger patties.

In response to the growing demand for plant-based meat alternatives, this study explores the impact of incorporating wheat gluten (WG) into soy protein isolate (SPI) on both the proximate and functional properties of protein blends. The research also examines the effects of high moisture extrusion processing, varying feed moisture levels (60%, 65%, and 70%), and WG-SPI blends on extruder response, as well as the textural, rheological, and solubility characteristics of the resulting extruded meat analogues. Moreover, the prime objective was to gain insights into the impact of using HMMA made at different ratios and feed moisture levels on plant-based burgers. As the WG incorporation level increased in SPI, the RVA viscosity, water absorption, and oil absorption capacities, and foaming stability exhibited a decrease while foaming capacity increased. As feed moisture and WG incorporation levels in SPI increased, the system parameters, rheological, and textural parameters of high moisture extruded meat analogs decreased. WG25-SPI75 showed the highest degree of texturization or sulfide bonds, and its extruded meat analogues at 60% feed moisture level burger patties resemble a similar textural to a chicken burger patty. This study is pivotal in understanding how wheat gluten in SPIs and feeding moisture level influence the textural and rheology properties of HMMA.

Relationship between rheological parameters and structure formation in high moisture extrusion of plant protein biopolymers

High moisture extrusion (HME) is widely employed to texturize plant-derived protein ingredients, but its development is still much based on trial and error. In this project, it was hypothesized that the rheological properties of plant-based mixtures analyzed when in the molten state and during their cooling can aid in understanding their structure formation. To test this hypothesis, biopolymer formulations containing pea protein isolate (PPI) were examined at different moisture and starch contents, and their rheological properties were analyzed using a closed cavity rheometer (CCR) at temperatures relevant to those applied during HME processing. The results obtained with the CCR were then contrasted with the mechanical properties of HME obtained using a lab scale extruder, measured using oscillatory rheology, large deformation, and dynamic mechanical analysis. Low moisture (55 %) HMEs were stiff and brittle, while high moisture (65 %) HMEs formed more flexible and anisotropic structures. Addition of starch created softer structures. The viscoelastic properties of the biopolymer mixes measured with the CCR were correlated with the mechanical parameters of the final extrudates. Strong correlations were found between small deformation rheological parameters measured in the CCR and the hardness values, while non-linear viscoelastic parameters were correlated with anisotropy indexes. Results demonstrated that the material properties measured at the early cooling stages strongly influence the structural heterogeneity in HMEs. This study highlights the potential to use the viscoelastic properties of the biopolymer mix measured with the CCR to predict their structural features when processed by extrusion.

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.

Structuring chicken breast analogs via high moisture extrusion of dairy-plant proteins blends

Chicken analogs were structured using binary blends of soy protein isolate (SPI) and wheat gluten (WG) or whey protein concentrate (WPC), as well as trinary blends of SPI-WG-WPC via high moisture extrusion. Chicken analogs with anisotropic structures were achieved (anisotropic index >1). Although adding WPC increased hardness, by varying the ratio of SPI to WG in the trinary blends, comparable texture profile properties as cooked chicken breast were achieved. The drivers of the fiber structure formation were non-covalent protein-protein interactions like hydrogen bonds and hydrophobic interactions, and to a lesser extent, inter-protein disulfide bonds formation. β-sheets were the dominant secondary structure, and adding WPC increased the proportion of α-helix while adding WG increased the proportion of β-turns in the meat analog (MA). This study offered strategies on structuring extruded chicken analogs with WPC, a high-quality protein source, and provided insights into mechanisms underlying the formation of fiber structures.

Tailoring enzyme modified starch through high-moisture extrusion: Unraveling structure-property relationships

The conventional method of producing enzyme modified starch (ES) involves using a dilute starch suspension, which necessitated substantial heat expenditure for drying the product and resulted in significant energy waste. Improved extrusion cooking technology (IECT) could extrude materials under high moisture, and it is a new physical modification technology. A comprehensive investigation was undertaken to produce enzyme modified starch (ES) with varying dextrose equivalent (DE) using IECT. The study systematically explored the effects of different screw speeds on the resulting IECT-ES properties. And principal component analysis and artificial neural network analysis were used to explore the correlation between data and the synaptic weight relationships. Results indicated that Maltese cross of IECT-ES disappeared, the R1047/1022 and R995/1022 decreased to 0.7305 and 0.9012 respectively, the full width at half maximum at 480 cm−1 increased to 26.81 %, light transmittance increased to 21.20 % and DE value rose to 14.19 % at 300 rpm. The properties evolution of IECT-ES was closely related to changes in structure and conditions. This study aimed to evaluate the effectiveness of IECT as an alternative method for producing enzyme modified starch. The findings provide valuable insights into more energy-efficient starch modification processes.

Evaluating the synergistic effects of sesame cake powder and soy protein isolate on rheological, textural, nutritional, and phenolic profiles of high-moisture extrusion processed meat analogs.

In this study, the high-moisture meat analogs (HmMAs) were developed by incorporating defatted sesame cake powder (DSP) in soy protein isolate (SyPI). The quality attributes of HmMA like visual appearance, specific mechanical energy (SME), mass flow rate (MFR), phenolic profile, textural and rheological properties were assessed after varying DSP concentrations (0%, 20%, 40%, and 60% w/w) and feed moisture (FM) levels (55% and 60%). The HmMA1 (derived solely from SyPI) exhibited higher hardness, chewiness, gumminess, cohesiveness, and springiness. The HmMA prepared from SyPI-DSP blends (HmMA2-8) demonstrated significant improvements in nutritional composition, and their visual characteristics indicated noticeable anisotropy. The interaction between SyPI and DSP influenced the quality of HmMA. Thehigher DSP concentration led to higher MFR and deeper curvatures of U-shaped structures, whereas lower SMS, textural and rheological properties. The DSP incorporation and 55% FM adjustments allowed mimicking meat cuts with thick fiber, influenced color, and proved advantageous in developing white meat analogs with higher free phenolics. The findings of the study suggest avenues for exploring DSP at a suitable level in SyPI for the development of better quality meat analogs.

Application of a shear cell for the simulation of extrusion to test the structurability of raw materials

The required raw material properties and the mechanisms behind fibrous structure formation during high moisture extrusion cooking (HMEC) to produce plant-based meat analogues are not sufficiently understood. The implementation of new raw materials is therefore a labour-intensive, empirical endeavour. Hence, this research explores the potential of a high-pressure shear cell (HPSC) as a tool for rapid screening of raw materials for HMEC suitability. During these texturisation tests, material viscosity was monitored to gain deeper mechanistic insights. For that, hydrated pea protein isolate (PPI) and soy protein concentrate (SPC) were sheared at 5-40 s−1 in the HPSC with a cone-plate or plate-plate geometry under extrusion-like conditions at 140–160 °C and 20 bar. Fibrous structures were successfully generated with both tested plant proteins, but reproducibility was limited to trials with SPC. Monitoring of viscoelastic properties revealed an onsetting polymerisation, followed by a decrease in viscosity, indicating fracturing of the forming network as underlying structuring mechanism. The suggested fracturing of an emerging network aligns with an observed increase in fibrousness in the plate-plate geometry compared to the cone-plate geometry due to the radial shear rate gradient. Finally, this research showcased a high similarity of the process-structure response pattern for SPC between the applied HPSC process and HMEC. Yet, further modifications, such as increasing the mechanical energy input capacity, are required to effectively apply HPSC processing for the prediction of the structuring behaviour in HMEC for the broad range of existing raw materials.

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.

Quantification of phase separation in high moisture soy protein extrudates by NMR and MRI

High-moisture (HM) extrusion is the dominant industrial process to create structured plant-based protein products that can be used for animal-free meat alternatives. Yet, the underlying mechanisms, such as phase separation, that govern structure formation in plant-protein extrudates, are still poorly understood. Current hypotheses require experimental data in order to be verified, but measurement techniques able to quantify phase-separated anisotropic protein extrudates are lacking, or have yet to be validated. In this study, Low-Field Time Domain (LF TD)-NMR and High-Field (HF) MRI techniques have been employed to unravel phase separation in HM extrudates of soy proteins. Results show that swelling with water enhances the 1H NMR/MRI signal-to-noise ratio in the measurements and unveils the presence of lamellar regions, while freeze-thawing enhances phase separation due to freeze concentration. Phase separation could be quantified by the observation of two distinct populations by LF TD-NMR T2 measurements. MRI images of dead-stop ribbon samples from HM extrusion revealed how the thickness of the aligned lamellar regions increases during passage of the protein melt through the cooling die. We conclude that TD-NMR can quantify phase separation, while spin-echo MRI can spatially resolve the lamellar structure conformation of HM extrudates. Thus, NMR and MRI are powerful techniques for non-invasively characterizing ex situ structure formation during HM extrusion, and for validating hypotheses on shear- and temperature-induced phase separation.

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.

High moisture extrusion of pulse proteins: Texture, structure, and in vitro digestion characteristics of extrudates

Pulse proteins are promising components for plant-based food development, yet their diverse subunit compositions, influenced by source origin, result in variable extrusion properties. This study utilized high moisture extrusion (60% moisture content) to prepare extrudates from four pulse proteins: soy, pea, chickpea and mung bean protein isolates (SPI, PPI, CPI, and MPI, respectively). The texture, structure, and in vitro digestion characteristics of extrudates were examined. The results showed that SPI and PPI were mainly composed of 7S and 11S globulins, while CPI and MPI were mainly composed of 7S globulins, and 11S globulins, respectively. SPI extrudates exhibited significantly lower hardness, chewiness, and transverse and longitudinal fracture stresses, while CPI extrudates exhibited a higher anisotropy index. SPI extrudates with a higher β-sheet content (39.08%) exhibited denser structures. The gastrointestinal digestibility (86.65%) of CPI extrudates was higher than other groups. Correlation analysis showed that 7S/11S ratio was positively correlated with the melt viscosity, while negatively correlated with the anisotropy index and in vitro digestibility. This study highlights the distinct extrusion properties of pulse proteins based on their unique subunit composition. The results provide insights for selecting appropriate protein sources and developing plant-based protein products with tailored textural attributes and desirable digestibility.

Quality characteristics and fibrous structure formation mechanism of walnut protein and wheat gluten meat analogues during high-moisture extrusion cooking process

Blending two or more materials to create better high-moisture meat analogues has been actively studied in the food science and technology field. Walnut protein is a high-quality plant-based protein resource, yet its full potential remains underexploited. Thus, this study focused on exploring the quality characteristics and fibrous structure formation mechanism of walnut protein (WP) and wheat gluten (WG) meat analogues during high-moisture extrusion cooking process. Results showed that the optimized WP and WG-blended high-moisture meat analogues exhibited a more pronounced anisotropic and oriented fibrous structure. The blending of WP and WG can protect the molecular chains from the thermal transition, and promote the aggregation of protein molecules mainly by enhancing the interaction between hydrophobic interactions and hydrogen bonds, increasing the apparent viscosity and forming protein subunits with larger molecular weights (>100 kDa) to stabilize the newly formed conformation. Additionally, the content of α-helix was the highest among the secondary structures. This study provides a theoretical basis for the application of WG and WP to produce HMMAs with rich fibrous structures.

Development and characterization of fibrous high moisture extrudates based on pea protein isolate and whey protein.

Construction of meat analogs based on pea protein isolate (PPI) alone by high moisture extrusion (HME) is diffocult as a result of the lack of anisotropic structures. In the present study, 0%-15% of whey protein (WP) was introduced to PPI to make hybrid blends, which were used to construct HME extrudates. WP enhanced the hardness, adhesive, cohesiveness and gumminess of the extrudates and facilitated the formation of a distinct anisotropic structure of PPI. The fibrous degrees of the extrudates containing 10% and 15% WP were around 1.50. The addition of WP, which has more -SH groups, increased the disulfide bonds and hydrogen bonding in the extrudates, leading to a denser cross-linked structure. Particle size distribution and Fourier transform infrared analysis showed that WP induced more compact structured aggregates and more β-sheet structures in the extrudates. Furthermore, the higher hydration capacity of WP may also help form a dilute melt and generate a more pronounced plug flow, assisting the formation of fiber structures of PPI. The present study demonstrates that WP is a potential modifier, which could be used to improve the structure of PPI-based meat analogs. © 2024 Society of Chemical Industry.

Textural improvement of pea protein-based high-moisture extrudates with corn zein and rice starch

High moisture extrusion allows the production of plant protein-based products, including meat analogues. Building upon our previous findings showing that zein mixed with rice starch provides the necessary textural properties to formulations, different pea protein-based formulations with varying amounts of zein and rice starch or wheat gluten (as control) were produced using high moisture extrusion and the rheological, textural, and microstructural characteristics were evaluated and associated with the secondary structure of proteins. Samples containing wheat gluten presented desirable rheological and mechanical properties in terms of texturization, which was evidenced by the generation of a layered and three-dimensional viscoelastic network. The addition of rice starch to zein significantly increased the viscoelasticity of the samples due to enhanced development of non-covalent interactions that led to higher and more stable β-sheets content and to the formation of a fibrous and layered microstructure and a 3D network nearly like those obtained with gluten. The sole replacement of pea protein by zein was not enough to develop these desired characteristics, demonstrating the importance of the non-covalent interactions between rice starch and zein for the generation of these properties. Overall, zein and rice starch improved texturization of pea protein-based gluten-free analogues made by high moisture extrusion.

Structural and functional properties of a high moisture extruded mixture of pea proteins (Pisum sativum), amaranth flour (Amaranthus hypochondriacus), and oat flour (Avena sativa)

Textured vegetable proteins (TVP) are an alternative to meet the increasing demand for non-animal food. This study aimed to develop a TVP from mixtures with 45 % pea protein isolate (PPI) enriched with amaranth (AF) and oat (OF) flours using high-moisture extrusion technology (HME) varying the moisture (50–70 %) and the temperature in the second heating zone of the extruder (110–140 °C). After extrusion, all samples demonstrated higher values of water absorption capacity (WAC) than non-extruded mixtures. Mixture of AF:OF:PPI (40:15:45 %) extruded at 60 % moisture and 135 °C showed promising functional properties with WAC and WSI values of 3.2 ± 0.2 g H2O/g and 24.89 ± 2.31 %, respectively, and oil absorption capacity (OAC) of 1.3 g oil/g. The extrusion process altered the thermal and structural properties of proteins promoting a desirable fibrous structure. This confirms the feasibility of using HME to develop TVP based on PPI, AF, and OF.

Binding and distribution regularity of water molecules in high-moisture textured Antarctic krill (Euphausia superba) meat

High-moisture extrusion technique with the advantage of high efficiency and low energy consumption is a promising strategy for processing Antarctic krill meat. Consequently, this study aimed to prepare high-moisture textured Antarctic krill meat (HMTAKM) with a rich fiber structure at different water contents (53 %, 57 %, and 61 %) and to reveal the binding and distribution regularity of water molecules, which is closely related to the fiber structure of HMTAKM and has been less studied. The hydrogen-bond network results indicated the presence of at least two or more types of water molecules with different hydrogen bonds. Increasing the water content of HMTAKM promoted the formation of hydrogen bonds between the water molecules and protein molecules, leading to the transition of the β-sheet to the α-helix. These findings offer a novel viable processing technique for Antarctic krill and a new understanding of the fiber formation of high-moisture textured proteins.

Multiscale study of structure formation in high moisture extruded plant protein biopolymer mixes

While high moisture extrusion (HME) of plant proteins is known to result in anisotropic structures, there are still gaps in understanding the principles underlying structure formation, as well as how to study the interactions between biopolymers in mixed systems. This study aims to employ advanced rheological and microstructural tools to better characterize the structure of various HME systems and to derive some general principles for their structure formation. Pea protein isolate, with and without starch, and less refined protein fractions from pea and faba bean were used to produce extrudates with varying structures. Mechanical properties were assessed using Texture Profile Analysis, Dynamic Mechanical Analysis (DMA), and oscillatory rheology, while microstructural insights were obtained through Confocal Laser Scanning and Confocal Raman Microscopy. The addition of maize starch resulted in softer extrudates with clear partitions between protein and starch domains. The different formulations used in this study also suggest the important role of different complex carbohydrates in structure formation. Distinct parabolic shapes were observed in the extrudates, suggesting that lamellae formed during cooling, influenced by melt viscosity and the laminar flow profile resulting from the temperature gradient across the cooling die. DMA was particularly useful in evaluating differences in mechanical behavior and anisotropy. Raman microscopy proved to be valuable in assessing spatial distribution of various components and providing insights of water mobility related to competition. Evaluating various biopolymer mixes allowed for a more general view into the mechanisms of formation of structure in HME, important to enhance the development of plant-based foods.

Impact of Extrusion Parameters on the Formation of Nε-(Carboxymethyl)lysine, Nε-(Carboxyethyl)lysine and Acrylamide in Plant-Based Meat Analogues.

To investigate the impact of extrusion parameters on the formation of Nε-(carboxymethyl)lysine (CML), Nε-(carboxyethyl)lysine (CEL) and acrylamide in plant-based meat analogues (PBMAs), the content changes and the correlations of compounds related to their formation were studied. The extrusion promoted CML, CEL and acrylamide formation, with more CEL being formed than CML. Variations in the moisture level and barrel temperature exerted a greater influence on the CML, CEL, acrylamide and α-dicarbonyl compounds than the screw speed and the feed rate. An increase in the moisture content led to a decrease in the CEL content, whereas it enhanced CML formation. The impact of moisture on acrylamide formation varied depending on whether low- or high-moisture extrusion was applied. Elevated temperatures promoted the accumulation of CEL, methylglyoxal and 2,3-butanedione while diminishing the accumulation of CML, acrylamide, glyoxal and 3-deoxyglucosone. CML and CEL were positively correlated with glyoxal and methylglyoxal, respectively. CEL and methylglyoxal were negatively correlated with protein and water content, whereas CML, glyoxal and 3-deoxyglucosone displayed positive correlations. In summary, higher moisture levels and feed rates and lower screw speeds and barrel temperatures are advantageous for producing PBMAs with lower CEL and total advanced glycation end-products contents, while lower or higher moisture contents, a lower feed rate and a higher barrel temperature are beneficial to reducing the acrylamide content.

Alaska pollock surimi-based meat analogs by high-moisture extrusion: Effect of konjac glucomannan/curdlan/carrageenan/sodium alginate on fibrous structure formation

This study investigated the effects of the addition of konjac glucomannan (KGM), curdlan (CD), carrageenan (CA), and sodium alginate (SA) on fibrous structure formation in surimi-based meat analogs to livestock meat. Meat analogs were prepared using high-moisture extrusion with Alaskan pollock surimi and soy protein isolate at a ratio of 7:3 (w/w). The meat analogs samples were labeled as SSP. Macrostructure observation showed that the best fibrous structure was obtained in SSP containing 2% SA. Mesostructure and microstructure observations revealed that 2% CD, CA or SA promoted the formation of a less tight three-dimensional network structure, which contributed to the formation of fiber filaments. Increased β-sheet structure content, ordered degree, fractal dimension and thermal stability were observed in SSP with the three colloids. Moreover, fibrous texture was closely associated with the thermal stability and fractal dimension. This study has provided useful information for colloid application in surimi-based meat analogs.

Elucidating the mechanism of inulin-induced improvement in the structural and functional properties of High-moisture extruded products

High-moisture extrusion (HME) has increasingly garnered attention in the production of plant-based meat analogs. Nevertheless, the disorganized structural properties and poor functional characteristics of HME extrudates pose significant challenges to the advancement of plant-based alternatives in the food industry. The coextrusion of proteins and polysaccharides has emerged as an effective strategy to improve the sensory qualities of HME meat analogs. Herein, we investigated the effects of the type and addition of inulin on the structural and functional properties of HME extrudates comprising soy protein isolate, soy protein concentrate, and wheat protein. The results indicated that inulin facilitated the conversion of 7S to 11S globulin and induced a transformation from a β-turn angle to a β-folded protein structure, promoting lamellar structure formation and enhancing the overall stability of the protein matrix. Optimal results were achieved with the addition of 6% long-chain and short-chain inulin. In terms of functional characteristics, the incorporation of short-chain inulin resulted in a superior fiber structure and protein digestibility, whereas long-chain inulin enhanced the water-holding capacity, rehydration rate, and thermal stability. Additionally, intermolecular interaction analysis revealed that these inulin-induced improvements in the quality of HME extrudates are primarily attributed to the strengthening of disulfide bonds and hydrogen bonds. These findings offer crucial insights for advancing the quality of plant-based meat analogs, providing valuable directions for future product development in the food industry.