High Moisture Extrusion Research Articles

Investigation of the Effect of Rice Bran Content on the Antioxidant Capacity and Related Molecular Conformations of Plant-Based Simulated Meat Based on Raman Spectroscopy.

At present, plant-based simulated meat is attracting more and more attention as a meat substitute. This study discusses the possibility of partial substitution of rice bran (RB) for soybean protein isolate (SPI) in preparing plant-based simulated meat. RB was added to SPI at 0%, 5%, 10%, 15%, and 20% to prepare RB-SPI plant-based simulated meat by the high moisture extrusion technique. RB-SPI plant-based simulated meat revealed greater polyphenol content and preferable antioxidant capacity (DPPH radical scavenging capacity, ABTS scavenging ability, and FRAP antioxidant capacity) compared to SPI plant-based simulated meat. The aromatic amino acids (tryptophan and tyrosine) of RB-SPI plant-based simulated meats tend to be masked first, and then the hydrophobic groups are exposed as RB content increases and the polarity of the surrounding environment increases due to the change in the disulfide conformation of RB-SPI plant-based simulated meats from a stable gauche-gauche-gauche conformation to a trans-gauche-trans conformation.

Mechanism of high-moisture extruded protein fibrous structure formation based on the interactions among pea protein, amylopectin, and stearic acid

During high-moisture extrusion (HME) processing for plant protein texturization, the interactions among proteins, starch and lipids should determine the formation of fibrous structures, which has not been confirmed systematically. In this study, the mechanism of protein fibrous structure formation during HME processing (58% moisture) was investigated based on the intermolecular interactions among the pea protein, amylopectin and stearic acid. Results suggested that the amylopectin and stearic acid synergistically contributed to improve the fibrous structures such as the hardness and fibrous degree in pea protein extrudate. In the extruder barrel, the complexation among the protein with amylopectin and stearic acid gave rise to the formation of aggregates with higher thermal stability and delayed the formation of protein gel network. In the die, the amylopectin and stearic acid weakened the hydrogen bonds between proteins and hindered the aggregation of legumin and vicilin subunits. In the cooling zone and extrudate, the amylopectin and stearic acid promoted the formation of fibrous structures through an “anchor orientation and flexible cross-linking” mechanism. Namely, the stearic acid as anchors hindered the refolding of protein molecular chains, while the amylopectin promoted the rearrangement, cross-linking and aggregation of protein molecules. The amylopectin and stearic acid synergistically weakened the interaction forces between proteins and led to the formation of more flexible structures in aggregates, which was favorable for the orientation and formation of anisotropic fibrous structures in extrudates. This study provided a theoretical basis for the development and improvement of the plant-based meat substitutes.

The flavor of faba bean ingredients and extrudates: Chemical and sensory properties

Faba bean, processed into ingredients (flour, protein concentrate, protein isolate), can be extruded to meat alternatives with a fibrous texture. Despite its importance for consumer acceptance, not enough is known about the flavor of faba bean ingredients nor about the chemical and sensory changes caused by high-moisture extrusion. Therefore, the aim of this work was to describe the flavor of faba bean ingredients and the corresponding extrudates and to understand how their composition affects the perception of sensory attributes. Firstly, faba bean protein ingredients and extrudates were characterized for lipid-degrading enzymatic activities, flavor precursors, and volatile and non-volatile flavor-active compounds. Secondly, sensory profiling was conducted. Thirdly, partial least squares regression was applied to understand the relationship between chemical and sensory data. This study showed that faba bean protein concentrate had the strongest taste and aftertaste (respectively 7 and 6, on a 0–10 intensity scale), bitterness (6–7), and pea flavor and odor (respectively 6 and 5), whereas faba bean protein isolate had the strongest cereal flavor (4) and odor (4), and off-flavor (2) and off-odor (3). Faba bean flour had the mildest flavor. High-moisture extrusion brought several chemical changes to the ingredients, including the formation of several volatile compounds and inactivation of lipid-degrading enzymes. Only traces of tannins were found in extrudates. The presence of free phenolics, vicine, and convicine was linked to strong taste and aftertaste, bitterness, and a drying sensation of the mouth, whereas lipid oxidation products were related to pea, cereal, and off-odors and flavors.

Die dimensions impact on fibrous plant protein formation during high moisture extrusion

Plant-based meat analogues that mimic the structure and texture of meat are becoming very popular. They can be produced using high moisture extrusion (HSE). . High protein materials first undergo intense thermomechanical treatment in the extruder barrel and then are textured and simultaneously cooled in the die. The mechanisms underlying this structuring process are not sufficiently understood and depend on numerous and interconnected factors, including raw materials composition and process parameters. This study focuses on the effects of die height and die length on extruder responses (torque, pressure), textural properties and fibration of soy concentrate extrudate obtained at high moisture (60% w/w). In order to evaluation the quality of fibration, and to complete texture analysis, a visual method base on angle of fibration was developed. By comparing extrudate obtained with die of 2 mm and 5 mm height, this study shows that a minimum height is necessary for temperature gradient and velocity profile creation in the die. In order to study die length higher than the one observed in the literature, a modular die with different lengths was specially developed for this study, going from 150 to 600 mm for a extrusion barrel length of 640 mm. Results show a linear correlation between fibration and die length: the longer is the die, the more elongated is the internal flow pattern. This change in flow pattern leads to an improvement in the quality of the extrudate fibration.It confirms that die length is one of the main influencing factor for fiber formation, and that a minimum length is required to obtain extrudats which structure really mimics meat fibres.

Effects of adding other protein products on textural properties of soy protein concentrate-based meat analogs.

In this study, we investigated the effects of proteins on the properties of soy protein concentrate-based meat analogs under high-moisture extrusion conditions. The rheological properties of soy protein concentration-sodium alginate (SPC-SA) and soy protein isolate-SPC-SA (SPI-SPC-SA), pea protein isolate-SPC-SA (PPI-SPC-SA), and zein-SPC-SA were evaluated, and the texture properties, microstructure, water absorption, and cooking properties of the resulting protein-meat analogs were characterized after addition of the protein raw materials. Results obtained indicated that the raw material containing 30% SPI had the best viscoelasticity, and the hardness and chewiness of resulting meat analog analogs were the highest when 30% SPI was added, along with the largest volume and best water absorption after cooking. The degree of texturization and toughness of meat analogs were the highest when PPI and zein were 30 and 50%, respectively. Results from this study showed that the texture properties of soy protein concentrate-based meat analogs were improved by adding proteins to raw material, thus providing a theoretical basis for further development of soy protein concentrate-based meat analogs.

Effects of Cysteine on Physicochemical Properties of High-Moisture Extrudates Prepared from Plant Protein.

The effects of cysteine addition (0%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%) on the physicochemical properties of plant-based extrudates by high-moisture extrusion were investigated. The texturization degree, rheological properties, hardness, springiness and chewiness of the extrudates significantly improved with the addition of cysteine (<0.15%). Analysis of the microstructure showed that the addition of cysteine (<0.15%) improved the formation of the fiber structure in the extrudates. Cysteine (<0.15%) promoted the formation of new disulfide bonds and non-covalent bonds by changing the disulfide bonds of protein molecules and enhanced the cross-linking degree between proteins. However, the excessive addition of cysteine (>0.15%) had a negative impact on the formation of fiber structure. Analysis of secondary structure suggested that the ordered β-sheet structures gradually converted to the disordered β-turn and random coil structures with the addition of cysteine (>0.15%). In addition, analysis of odor properties with the addition of cysteine using an electronic nose showed the difference in volatile components of the extrudates mainly existed in halides, hydrocarbons, sulfides and amines. On the whole, the addition of cysteine could improve the quality of plant-based extrudates.

Novel rotating die coupled to a twin-screw extruder as a new route to produce meat analogues with soy, pea and gluten

Modern plant-based meat analogues should have a pronounced fibrous structure as an important characteristic. In this study, we demonstrate that the combination of high moisture extrusion cooking (HMEC) with well-defined shear during cooling is a new process to make fibrous products using common meat analogue ingredients. The shear was applied via a cooling die attached to the extruder that was specially designed for that purpose. The in–house developed cooling die consists of two sequential rotating inner cylinders with a separate drive-unit in an outer cylinder that can be thermo-regulated. Three rotational speeds of the inner cylinder, 45, 75 and 105 min−1, were tested for pea protein isolate, soy protein concentrate, vital wheat gluten and blends of pea or soy with gluten. A large effect on macro- and micro-texture and anisotropy index was found when the concentration of gluten was increased. The different ingredients and blends had different optimal conditions and reacted differently to the applied shear. Interestingly, the angle of the fibers observed in the samples differed at the different rotational speeds. This was attributed to the shear thinning behavior of the plant proteins and the velocity gradient in the rotating die, arising from the temperature and viscosity gradient. The ability to change the shear rate as an independent parameter in the rotating cooling die is unique and allows texture adjustments during processing. This is an important improvement for industrial HMEC and opens new product design possibilities.

Physicochemical and structural properties of meat analogues from yeast and soy protein prepared via high-moisture extrusion

In this study, yeast and soy protein at different ratios (0:1, 1:9, 2:8, 3:7, 4:6, and 5:5) were used to produce meat analogues (MA) via high-moisture extrusion. According to color analysis, the addition of yeast protein (YP) increased the lightness of MA from 43.12 ± 0.26 (the control) to 50.37 ± 0.46 (50 g/100 g, dry basis). Textural results indicated that when the YP content was 40 g/100 g (dry basis), the hardness, chewiness, and fibrous degree of MA reached the maximum (523.94 ± 11.91 N, 724.55 ± 22.89 N, and 2.06 ± 0.15, respectively), which were higher than the control (419.63 ± 7.52 N, 618.02 ± 14.82 N, and 1.43 ± 0.03, respectively). Furthermore, YP increased the free water ratio, SS bond, and total β-sheets structure content, while reducing the β-turn structure content and thermal stability of MA. Overall, YP is a promising protein source for preparing high-quality MA.

Microscopic insight into the interactions between pea protein and fatty acids during high-moisture extrusion processing

To provide a theoretical basis for the quality improvement of plant protein-based meat substitutes with lipids, the interactions between pea protein and fatty acids (stearic, oleic and linoleic acids) and the effect on protein conformational changes during high-moisture extrusion (HME) processing were investigated using a dead-stop operation. The surface hydrophobicity analysis and Fourier transform infrared spectroscopy results revealed that the fatty acids induced the exposure of hydrophobic groups in the pea proteins, weakened hydrogen bonds, affected the aggregation of legumin subunits and promoted the conversion of α-helix and β-sheet structures to β-turn and random coil during HME processing. In the die, unsaturated fatty acids limited the refolding of protein chains and covalent interactions between proteins. Micromorphology analysis indicated that the coalescence of oleic and linoleic acids in the cooling zone hindered the formation of anisotropic structures while stearic acid promoted the formation of fibrous structures by enhanced disulfide bonds.

Rheological properties of transglutaminase-treated concentrated pea protein under conditions relevant to high-moisture extrusion processing.

At present, the structural changes of extruded materials under thermal-mechanical stress during high-moisture extrusion are still unclear. In this study, the transglutaminase (TG) treatments on the structure of pea protein isolate (PPI) under conditions relevant to high-moisture extrusion processing (50 wt% PPI at 30°C, 120°C and heated to 120°C and subsequently cooled to 30°C) was studied by using a closed cavity rheometer. Strain and frequency sweeping were carried out under various temperature conditions, and the information obtained was drawn into a texture map. Lissajous curves combined with energy dissipation ratio were introduced to characterize the nonlinear response of the samples. The results showed that the storage modulus of PPI increased with the increase of TG concentration during heat treatment. After cooling to 30°C, PPI with 0.25–1%TG could enhance the elasticity, but treating by 2% TG could inhibit the formation of disulfide bonds, the uniform development of the protein network, thus showing the “tough” character. These findings can help to better understand the relationships of material-structure during the extrusion process, and also provide help for further optimization of the quality of meat substitutes.

The texture of plant protein-based meat analogs by high moisture extrusion: A review.

Meat analogs produced by high moisture extrusion (HME) are considered to be one of the products that have great potential for replacing real meat. The key issue as a meat analog is whether the texture can meet the standards of real meat. Nowadays, there have been some advances in the textural characterization of meat analogs, which are discussed in detail in this review. Firstly, this review describes the current characterizations of meat analogs in terms of fiber structure, hardness, springiness, tensile resistant force and sensory evaluation. Then, methods for analyzing the texture of meat analogs, such as texture analyzer, microstructure-based methods, and other methods for characterizing fiber structure, are summarized. In addition, these characterizations are discussed in relation to the factors that influence the texture of meat analogs during HME. Finally, we propose priorities and some promising methods for future meat analogs conformation studies.

Effects of oyster mushroom addition on quality characteristics of full fat soy‐based analog burger patty by extrusion process

AbstractThe effects of oyster mushroom (Pleurotus ostreatus) addition on quality characteristics of full fat soy (FFS) and isolated soy protein (ISP)‐based analog burger patties by extrusion process were compared and investigated. Oyster mushroom added to the base mixtures (FFS and ISP) as different levels (0%, 4%, 8%, and 12%), which were texturized by using the twin‐screw extruder equipped with cooling die. After extrusion cooking, in comparison on meat analogs and its analog burger patty, ISP‐based meat analog had the higher textural properties including hardness, springiness, cohesiveness, and chewiness than FFS‐based meat analog. Textural properties of ISP‐based meat analog consistently also increased with the increase in oyster mushroom contents (p &lt; .05), while FFS‐based meat analog had the inconstant patterns in the springiness and cohesiveness, and it obtained the higher cutting strength than ISP‐based. In contrast, in its analog burger patty, the consistent patterns exhibited in all the FFS‐based. Moreover, FFS‐based had the higher textural properties (p &lt; .05) with cutting strength than ISP‐based burger patty. The highest water holding capacity, cooking properties, and organoleptic properties were also observed in FFS‐based analog burger patty with 12% oyster mushroom content except meat patty. Overall, this study suggested that the addition of the oyster mushroom into the analog burger patties improved the overall quality, and FFS could be possible to potential alternative of soy material for analog burger patty.Practical ApplicationsPlant‐proteins for analog burger patty are the high cost and required with several steps for purifying process. In addition, meat analog commonly exhibits the weak texture, and almost tasteless, which has resulted in the use of excessive seasoning, flavoring, adding the binding agent. Oyster mushroom (Pleurotus ostreatus) has played an important role as additive which could enhance the texture and organoleptic quality of analog burger patty by using the high moisture extrusion technology. This work demonstrated that addition of oyster mushroom into the full fat soy‐based formation that has health benefits, cost effectiveness and environmentally friendly could offer the high‐quality burger patty to the consumers who might have concern of negative issues on meat as well as vegetarian.

Plant-based meat substitutes by high-moisture extrusion: Visualizing the whole process in data systematically from raw material to the products

High-moisture extrusion technology should be considered one of the best choices for producing plant-based meat substitutes with the rich fibrous structure offered by real animal meat products. Unfortunately, the extrusion process has been seen as a “black box” with limited information about what occurs inside, causing serious obstacles in developing meat substitutes. This study designed a high-moisture extrusion process and developed 10 new plant-based meat substitutes comparable to the fibrous structure of real animal meat. The study used the Feature-Augmented Principal Component Analysis (FA-PCA) method to visualize and understand the whole extrusion process in three ways systematically and accurately. It established six sets of mathematical models of the high-moisture extrusion process based on 8 000 pieces of data, including five types of parameters. The FA-PCA method improved the R2 values significantly compared with the PCA method. The Way 3 was the best to predict product quality (Z), demonstrating that the gradually molecular conformational changes (Yn´) were critical in controlling the final quality of the plant-based meat substitutes. Moreover, the first visualization platform software for the high-moisture extrusion process has been established to clearly show the “black box” by combining the virtual simulation technology. Through the software, some practice work such as equipment installation, parameter adjustment, equipment disassembly, and data prediction can be easily achieved.

Identifying changes in soybean protein properties during high-moisture extrusion processing using dead-stop operation

To provide additional evidence and better understand the high-moisture texturing extrusion process of soybean protein isolate (SPI), the physico-chemical changes of SPI during extrusion were investigated. SPI in the extruder feeding zone, barrel zones 1 (80 °C) to 4 (135 °C), and the cooling die (80 °C) were obtained from a dead-stop operation. The lowest values associated with the denaturation enthalpy and the extractable protein occurred in zone 3 (150 °C). The minimum level of the protein subunit content was identified in zone 4. The highest value of the average protein molar mass occurred in zone 3. The β-sheet ratio in the protein increased, and the unordered ratio decreased after extrusion. The surface hydrophobicity of the protein decreased with water injection in zone 1; however, it increased in zone 2 (110 °C). Overall, SPI undergoes swelling, denaturation, aggregation, and depolymerization due to water injection, heating, and shearing during high-moisture extrusion.

Structural characteristics of high-moisture extrudates with oil-in-water emulsions

There is an increasing demand to produce high-quality plant-based meat analogs rich in tenderness and juiciness, presenting a significant challenge in creating oil-containing fibrous structures. A novel oil addition approach was developed by adding oil-in-water (O/W) emulsion during high-moisture extrusion processing. The current study investigated the effect of oil content using O/W emulsion on high-moisture extrudates prepared from soy protein isolate (SPI) and wheat gluten (WG) (SPI-WG). The oil content in fibrous SPI-WG extrudate could be up to 8.0% using O/W emulsion, whereas only 4.0% was possible by direct oil addition. O/W emulsion addition significantly decreased the extrusion response parameters of die pressure and specific mechanical energy. Confocal laser scanning microscopy indicated that oil was distributed to small droplets (0.5–15.0 μm) within the protein matrix in SPI-WG extrudates. Oil-free SPI-WG extrudate presented a close-meshed protein network. In contrast, higher oil contents led to more porous structures in SPI-WG extrudates with 3.0–8.0% oil. O/W emulsion addition reduced the rubber-like texture and rheological properties of SPI-WG extrudates, which improved the textural attributes (e.g., chewiness), making them similar to those of cooked chicken breast. In addition, the mobility of water and oil protons increased with increasing oil contents in SPI-WG extrudates, indicating the water and oil binding properties were reduced. Overall, this study demonstrated the potential of using O/W emulsions to promote fibrous structures of high-moisture extrudates.

Characterization and Cellular Uptake of Peptides Derived from In Vitro Digestion of Meat Analogues Produced by a Sustainable Extrusion Process.

Whether proteins in meat analogues (MAs) have the ability to provide equivalent nutrition as those in animal meat remains unknown. Herein, a MA was produced by high-moisture extrusion using soy and wheat proteins. The physicochemical properties, in vitro digestion, and cellular uptake of the released peptides were systematically compared between the MA and the chicken breast (CB). The MA showed a higher hardness but a lower degree of texturization than the CB. After simulated digestion, soluble peptides in the MA had a higher molecular weight and higher hydrophobicity. No observable cytotoxicity or inflammatory response to Caco-2 cells was found for both MA and CB digests. The former exhibited less permeability of peptides across Caco-2 cells. Liquid chromatography with tandem mass spectrometry found that the identified peptides in MA and CB digests contained 7-30 and 7-20 amino acid residues, respectively, and they became shorter after cellular transportation. The amino acid composition showed fewer essential and non-essential amino acids in the MA permeate than in the CB permeate.

High moisture extrusion of soy protein and wheat gluten blend: An underlying mechanism for the formation of fibrous structures

High moisture extrusion of soy protein concentrate (SPC) and wheat gluten (WG) blends was conducted to investigate the potential use of this mixture in the production of meat analogs. Extrusion samples collected at different zones from the extruder barrel and extrudates were analyzed to determine their texture, microstructure, protein solubility, secondary structure, and mode of disulfide bonds present in the molecular structure. Results obtained from this study indicate that a blend of SPC-WG at 50/50 resulted in the best fibrous structures. In comparison, extrudates prepared by either SPC or WG did not contain any clear fibrous structures. Additionally, hydrogen and disulfide bonds play a major role over extrusion, with a transformation of disulfide bonds from the intramolecular to intermolecular mode. The analysis of the secondary structure shows that the transformation from α-helix to β-sheet and the maintenance of an ideal balance are crucial for the formation of the fiber structure. The extrudate obtained at SPC-WG ratio of 50/50 presented very good rehydration characteristics when immersed in water at 60 °C for 40 min, due to WG promoting the formation of fibrous structures.

High-Moisture Extrusion of Mixed Proteins from Soy and Surimi: Effect of Protein Gelling Properties on the Product Quality.

The high-moisture extrusion of proteins from plant and animal sources should be a new way for developing alternative protein products with meat-like texture. The protein gelling properties are considered an important factor for the meat-like texture formation during the high-moisture extrusion processing. In this study, the mixed protein gelling properties from soy protein isolate (SPI) and surimi at different ratios (90:10, 80:20, 70:30, 60:40 and 50:50) were investigated to relate to the high-moisture (70%) extruding product textural properties, correspondingly. Results showed that at SPI–surimi ratio 60:40, the heat-induced gelation time was clearly extended and the gel strength became much weaker. During the high-moisture extrusion processing, at SPI–surimi ratio 80:20, the extrudate showed the higher hardness, chewiness, gel strength and fibrous degree, while excessive surimi (more than 40%) in the blends would hinder the fibrous-oriented structure formation. It suggested that SPI may act as the continuous phase that is dispersed by surimi during the high-moisture extrusion processing. Interestingly, it was found that the gel strength of SPI–surimi blends was nonlinearly correlated with the specific mechanical energy (SME) and product textural properties. The study would be helpful for improving the textural properties of alternative protein products from soy and surimi.

Effect of fatty acid saturation degree on the rheological properties of pea protein and its high-moisture extruded product quality

To provide a deep insight into the application of lipid in plant protein-based meat substitutes through high-moisture extrusion (HME) process, the effect of fatty acid saturation degree (stearic acid, oleic acid and linoleic acid) on the rheological and structural properties of pea protein isolate (PPI), and its relationship with the extrusion system parameters and extrudate qualities were investigated. The oleic acid and linoleic acid significantly decreased the apparent viscosity of PPI dispersion and thus reduced the die pressure and torque during HME processing. Electrophoresis and Fourier transform infrared spectroscopy results revealed that fatty acids inhibited the aggregation of legumin and vicilin subunits at 50 and 20 kDa, and promoted the conversion of α-helix and β-sheet to β-turn and random coil. The macro- and micro-structure observation and texture analysis suggested that the fatty acids with higher unsaturation degree were not advantageous for the pea protein fibrous structure improvement during HME process.

Physical Properties of Extrudates with Fibrous Structures Made of Faba Bean Protein Ingredients Using High Moisture Extrusion.

Faba bean is a potential ingredient due to its high protein yield and its possible cultivation in colder climate regions. In this study, meat analogues made from faba bean protein isolate (FPI) and concentrate (FPC) blends were produced using high moisture extrusion. The aim of this study was to investigate the effect of the FPI content (FPIc), feed water content (FWC), and temperature of the long cooling die (LT) during extrusion on the mechanical and physicochemical properties as well as on the structure of the meat analogues. Increased FPIc resulted in higher values in hardness, gumminess, chewiness, and cutting strengths as well as in darker colour and decreased water absorption capacity. The effect of increased FWC on these properties was weaker and the opposite. Images from microtomography revealed that higher FPIc led to a less organised fibrous structure. In conclusion, fibrous structures can be achieved by utilising a mixture of faba bean protein ingredients, and a higher FPC content seemed to promote fibre formation in the meat analogue.