Protein-amylose/amylopectin molecular interactions during high-moisture extruded texturization toward plant-based meat substitutes applications

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.

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.

High moisture extrusion of soybean protein isolate: Effect of β-glucan on physicochemical properties of extrudates

This study is focused on exploring the effect of twin-screw high-moisture extrusion technology on the physico-chemical properties of β-glucan-soybean protein isolate (SPI-BG) extrudates. Different proportions (0 %, 1 %, 2 %, 3 %, 4 %, 5 %) of oat β-glucan (BG) were added with soybean protein isolate (SPI) to prepare SPI-BG extrudates. Results showed that the addition of a high quantity of β-glucan (BG) decreased the elastic properties of soy protein isolate (SPI) extrudates and then increased. The strengthening of S1-S2-S3 interactions (hydrogen bonds, hydrophobic interactions, and disulfide bonds) was primarily responsible for this trend. Fourier transform infrared (FTIR) spectral analysis was conducted which revealed that BG did not significant affect random coil content of SPI. However, it was observed that α-helix content was increased significantly and the β-sheet content was decreased. An observation was noted in the value of enthalpy (ΔH) change that increased from 115.80 J/g to 159.68 J/g.

Flavor of extruded meat analogs: A review on composition, influencing factors, and analytical techniques

Meat analogs are anticipated to alleviate environmental and animal welfare concerns as the demand for meat rises. High moisture extrusion is commonly employed to produce meat analogs, and its flavor could influence consumers' choice. To improve the development and market demand of extruded meat analogs, flavor precursors and natural spices have been used in high moisture extrusion process to directly improve the flavor profile of extruded meat analogs. Although there have been many studies on the flavor of high moisture extruded meat analogs, flavor composition and influencing factors have not been summarized. Thus, this review systematically provides the main pleasant and unpleasant flavor-active substances with 79 compounds, as well as descriptive the influence of flavor-active compounds, chemical reactions (such as lipid oxidation and the Maillard reaction), and fiber structure formation (based on extrusion process, extrusion parameters, and raw materials) on flavor of extruded meat analogs. Flavor evaluation of extruded meat analogs will toward multiple assessment methods to fully and directly characterize the flavor of extruded meat analogs, especially machine learning techniques may help to predict and regulate the flavor characteristics of extruded meat analogs.

Effect of Starch Types on the Textural and Rehydration Properties of Extruded Peanut Protein Pore Gel Particles

In this study, the effect of different starches from corn, potato and pea containing varying amylose/amylopectin ratios on the textural and rehydration properties of extruded peanut protein gel particles were investigated. Results showed that textural and rehydration properties of peanut protein extruded with corn starch, potato starch and amylopectin are slightly inferior to those of peanut protein with pea starch extrudates. The addition of pea starch led to an increase in the pore structure of the peanut protein extrudates and improved their water absorption index, simultaneously reducing the hardness and density. Pea starch, as a natural water-absorbing expansion material, helped peanut protein to form cross-linked gel polymers that bind more water molecules, in addition to further polymerization with peanut protein, which made the protein secondary structure became disordered. These changes directly affected the textural properties of the extrudates. In addition, the blended system of starches and peanut protein tended to form more elastic solids, which affected the expansion of the extrudates. These findings indicate that starch can effectively improve the poor expansion of proteins, making it suitable for use in the production of plant protein-based foods.

Design of colloid structure to realize gel salt reduction: a review

Excessive consumption of salt is associated with increased incidence of cardiovascular diseases, hypertension, diabetes, and other health issues. However, it is challenging to find appropriate strategies that balance sensory qualities while achieving sodium reduction as salt plays a crucial role in providing desired appearance, texture, and taste. The impact of hydrocolloid properties (addition and type) on saltiness perception were reviewed. Additionally, considering the interactions between food components, both covalent and noncovalent, we propose designing specialized colloidal structures capable of binding sodium ions to enhance salt-taste perception. The effects of hydrocolloids on the physicochemical, structural, and sensory qualities of gel foods are then discussed. Finally, by addressing current issues with low-salt foods and consumer demands, we provide a future outlook for low-salt food development. The selection of suitable hydrocolloids and precise control of the addition are crucial considerations for achieving salt reduction. The interaction between hydrocolloids and other food components can be utilized to design specialized colloidal structures, thereby accomplishing gel-based salt reduction and enhancing properties. This review serves as a theoretical reference for developing healthy, nutritious, and flavorful low-salt foods that can aid in the prevention and mitigation of diseases associated with excessive salt consumption.

Mechanism of feed moisture levels in extrusion treatment to improve the instant properties of Chinese yam (Dioscorea opposita Thunb.) flour

Extruded yam flour was prepared at different feed moisture to improve its instant properties. The water solubility index (WSI) and water absorption index (WAI) were used to compare the instant properties of yam flour. Their chemical compositions, particle size distribution, crystalline structure, and microscopic forms were also analyzed to assess the effects of feed moisture on the instant properties of yam flour. We found that extrusion significantly improved the instant properties of yam flour, while the WSI value increased from 29.50% to 71.86% and the WAI value decreased from 387.88% to 228.06% with decreased feed moisture. Extrusion led to the degradation of total starch and amylopectin, and the contents of soluble substances increased markedly. Extrusion destroyed the granular and crystalline structures, which were reconstituted as amylose-lipid complexes with a significant decrease in relative crystallinity. Increasing the feed moisture was beneficial to the flow and color retention, while lower feed moisture was more favorable to enhance the instant properties.

Current Technologies and Future Perspective in Meat Analogs Made from Plant, Insect, and Mycoprotein Materials: A Review

This study reviewed the current data presented in the literature on developing meat analogs using plant-, insect-, and protein-derived materials and presents a conclusion on future perspectives. As a result of this study, it was found that the current products developed using plant-, insect-, and mycoprotein-derived materials still did not provide the quality of traditional meat products. Plant-derived meat analogs have been shown to use soybean-derived materials and beta-glucan or gluten, while insect-derived materials have been studied by mixing them with plant-derived materials. It is reported that the development of meat analogs using mycoprotein is somewhat insufficient compared to other materials, and safety issues should also be considered. Growth in the meat analog market, which includes products made using plant-, insect-, and mycoprotein-derived materials is reliant upon further research being conducted, as well as increased efforts for it to coexist alongside the traditional livestock industry. Additionally, it will become necessary to clearly define legal standards for meat analogs, such as their classification, characteristics, and product-labeling methods.

Changes in physicochemical and structural properties of pea protein during the high moisture extrusion process: Effects of carboxymethylcellulose sodium and different extrusion zones

This study investigated effects of carboxymethylcellulose sodium (CMC) on the conformational evolution of pea protein during the high moisture extrusion process. The morphological observation showed that the addition of CMC facilitated the formation of fibrous structure of pea protein. In comparison with the pea protein in the melting zone and extrudate, the combination of CMC increased the denaturation enthalpy of pea protein by 2.09 % and 2.34 %. Compared with the material in the mixing zone, the degree of grafting between CMC and pea protein in the die was enhanced by 98.95 %. In general, the supplementation of CMC depressed the exposure of hydrophobic groups in the pea protein. In the extrusion barrel, the CMC increased the unfolding of protein molecular chains while it promoted the refolding of protein chains in the die. For the extrudate, the addition of CMC decreased the contents of α-helix and β-sheet of pea protein by 9.67 % and 6.93 % while the contents of β-turn and random coil were increased, leading to changes in the molecular weight distribution of protein molecules. In conclusion, these results provided new strategies toward producing the high-quality pea protein-based meat analogues by adding CMC.

Evaluating the potential of millets as blend components with soy protein isolate in a high moisture extrusion system for improved texture, structure, and colour properties of meat analogues

This study explored the use of millets flours as a secondary ingredient with soy protein isolate (SPI) to develop fibrous high moisture meat analogue (HMMA). Three millets (sorghum, pearl millet, and finger millet) with three incorporation levels (10%, 20%, and 30%) were extruded at 60%, 65%, and 70% moisture content. The results showed that millet type, incorporation level, and moisture content significantly influenced the system parameters and textural properties. Good visual texturization was achieved at addition of pearl millet up to 30% incorporation level and sorghum and finger millet up to 20% incorporation level. Furthermore, the textural properties of HMMA made from SPI-millet blends were compared against HMMA made from SPI-gluten blend and real chicken. The HMMA made from SPI-millet flour had lower hardness, chewiness, resilience, springiness, tensile strength, cutting strength than that for SPI and SPI-wheat gluten blend and were much closer to corresponding values for real chicken. The results also showed that each of the three millet types generated distinctly different fibre patterns (thick to thin fibres) and colour (whiter to darker) of HMMA. Thus, HMMA produced from SPI-millet flour blends can offer a wide textural, fibre pattern and colour space for different plant-based meat applications. Since millets do not have gluten, they also offer an opportunity to make gluten-free HMMA's.

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.

Effects of Haematococcus pluvialis Addition on the Sensory Properties of Plant-Based Meat Analogues

Due to the increase in population and the deficiency of land resources, the cost of raising livestock is gradually increasing. Plant-based meat analogues (PBMAs) are considered excellent substitutes for animal meat. Our research investigated the effect of Haematococcus pluvialis (HP) on gluten-based soybean and wheat PBMA with contents of 1%, 3%, 5%, and 7%. Compared with the control group, HP significantly improved the color of the extrudates, showed visual characteristics similar to red meat, and achieved a soft texture and apparent rheological properties. The 7% HP had negative effects on the organizational degree and viscosity. In addition, the E-nose indicated that the different contents of HP changed the flavor of the extrudates. The extrudates with 3% and 5% HP were most similar to each other among all of the extrudates for volatile compounds, and the extrudates with 1% HP and 7% HP had significantly different flavors compared to the control group. Furthermore, 20 different volatile compounds were compared according to their retention indices and retention areas. The results showed that the proportions of alcohol, ester, terpenes, acid, and furan were increased. When the threshold was referenced, HP was considered to provide PBMAs with grassy and healing grain flavor properties. Therefore, the results proved that the addition of HP can improve PBMAs sensory properties.

Advanced tensile testing as a new tool to quantify properties of food

Mechanical properties of food products are regularly analysed by tensile tests. The aim of this study was to demonstrate the potential of using advanced tensile testing techniques to better understand the mechanical properties of anisotropic food products, such as meat analogues and certain dairy products. The effects of various tensile testing parameters, including tensile gauge length and deformation rate, on the interpretation of mechanical properties of meat analogues was studied. Additionally, digital image correlation, an image analysis technique, was used for true distance recording and analysis of fracturing behaviour of the products. An isotropic product was prepared from solely soy protein isolate, and an anisotropic product was prepared from soy protein isolate and pectin using the shear cell technology. The tensile properties of the products were studied with four different moulds with varying gauge lengths of 17.5, 15, 11.5, and 8.5 mm, and at three deformation rates of 46.2, 23.1, and 11.6 mm/min. A smaller gauge length and slower deformation rate improved visualization and interpretation of the multi-stage descending branch in force - distance curves of anisotropic products. Additionally, tensile parameters, specifically toughness, proved to be more accurate at small gauge length and slow deformation rate, because overestimation due to rapid crack propagation was prevented. True distance data obtained with digital image correlation further improved the interpretation of the fracturing behaviour of the products. Inhomogeneous strain distribution in anisotropic products was shown with digital image correlation, in contrast to the homogeneous strain distribution observed in isotropic products. Furthermore, the Poisson's ratio, obtained through digital image correlation, explained inherent differences in structure and plasticity between isotropic and anisotropic meat analogues. This study shows the importance of careful selection of testing parameters and techniques. Moreover, it advises the use of digital image correlation for better measurement of fracture mechanics and strain distribution.

Plant-based meat analogs and fat substitutes, structuring technology and protein digestion: A review

There is currently an increasing trend in the consumption of meat analogs and fat substitutes due to the health hazards by excessive consumption of meat. Simulating the texture and mouthfeel of meat through structured plant-derived polymers has become a popular processing method. In this review, the mechanical structuring technology of plant polymers for completely replacing real meat is mainly introduced in this review, which mainly focuses on the parameters and principles of mechanical equipment for the production of vegan meat. The difference in composition between plant meat and real meat is mainly reflected in the protein, and particular attention should be paid to the digestive characteristics of plant meat protein in the gastrointestinal tract. Therefore, the differences in the protein digestibility properties of meat analogs and real meat is discussed in this review, focusing primarily on protein digestibility and peptide/amino acid composition of mechanically structured vegan meats. In terms of fat substitutes for meat products, the types of plant polymer colloidal systems used for meat fat substitutes is comprehensively introduced, including emulsion, hydrogel and oleogel.

Molecular interactions between apigenin and starch with different amylose/amylopectin ratios revealed by X-ray diffraction, FT-IR and solid-state NMR

Starch can readily form complexes with polyphenols. However, its two components, namely amylose and amylopectin, differ significantly in their ability to complex with phenolic compounds. Given that the mechanism of their interaction is still poorly studied, this work investigated intermolecular interactions between apigenin and starch with different amylose/amylopectin ratios using ¹H NMR, FT-IR, XRD, DSC and solid-state NMR. Results showed that corn starch with high amylose/amylopectin ratios had a better complexing ability and higher complexing index with apigenin than amylopectin. Besides, solid-state NMR suggested that the molecular mechanism behind the strong intermolecular interactions between corn starch and apigenin involved hydrogen bonds. Furthermore, the detailed binding sites of hydrogen bonds, that linked by hydroxyl-starch and phenyl-apigenin were also confirmed by ¹H¹³C heteronuclear correlation (HETCOR) spectra. This study revealed the molecular mechanism on amylose/amylopectin complexing with apigenin and provides a theoretical basis for further developing polyphenols in starchy food.

Hypotheses concerning structuring of extruded meat analogs

In this paper, we review the physicochemical phenomena occurring during the structuring processes in the manufacturing of plant-based meat analogs via high-moisture-extrusion (HME). After the initial discussion on the input materials, we discuss the hypotheses behind the physics of the functional tasks that can be defined for HME. For these hypotheses, we have taken a broader view than only the scientific literature on plant-based meat analogs but incorporated also literature from soft matter physics and patent literature. Many of these hypotheses remain to be proven. Hence, we hope that this overview will inspire researchers to fill the still-open knowledge gaps concerning the multiscale structure of meat analogs.

Physicochemical and In Vitro Starch Residual Digestion Structures of Extruded Maize and Sorghum Starches Added with Sodium Stearoyl Lactylate

This research aimed to characterize the physicochemical, in vitro digestion, and structural features of digestion residues of maize and sorghum starches subjected to thermoplastic extrusion, along with the influence of Sodium Stearoyl Lactylate (SSL), to obtain improved starches for food applications and to understand their behavior when consumed as a food ingredient. The morphology of the extruded materials showed remanent starch granules when SSL was used. A higher amount of medium and large linear glucan chains were found in these particles, influencing higher thermal stability (ΔH ≈ 4 J/g) and a residual crystallinity arrangement varying from 7 to 17% in the extrudates. Such structural features were correlated with their digestibility, where slowly digestible starch (SDS) and resistant starch (RS) fractions ranged widely (from 18.28 to 27.88% and from 0.13 to 21.41%, respectively). By analyzing the data with a Principal component analysis (PCA), we found strong influences of B2 and B3 type chains on the thermal stability of the extrudates. The amylose and smaller glucan chains (A and B1) also significantly affected the emulsifying and foam stability properties. This research contributes to the molecular knowledge of starch in extruded products with broad food applications.

Application of transglutaminase modifications for improving protein fibrous structures from different sources by high-moisture extruding

Plant proteins can be extruded under high moisture content (above 40 %) to form meat-like fibrous structures, which is the basis for meat-like substitute products. However, the proteins' extrudability from various sources remain challenging in terms of generating fibrous structures under combinations of high-moisture extrusion with transglutaminase (TGase) modifications. In this study, proteins from soy (soy protein isolate, SPI, and soy protein concentrate, SPC), pea (pea protein isolate, PPI), peanut (peanut protein powder, PPP), wheat (wheat gluten, WG), and rice (rice protein isolate, RPI) were texturized using high-moisture extrusion combined with transglutaminase (TGase) modifications to enact changes in protein structure and extrusion capabilities. The results showed that soy proteins (SPI or SPC) responsed to torque, die pressure and temperature during extrusion, and this phenomenon was more pronounced at a higher protein content (SPI). In contrast, rice protein exhibited poor extrudability, leading to large losses of thermomechanical energy. TGase significantly affects the orientation of protein fibrous structures along the extrusion direction by impacting the rate of protein gelation during the high-moisture extrusion process, with the impact mainly occurring in the cooling die. Globulins (mainly 11S) played a major role in forming fibrous structures and the aggregation of globulins or reduction of gliadins under TGase modification impacted the orientation of the fibrous structure along the extrusion direction. Some thermomechanical treatment during high-moisture extrusion results in protein conversion from compact structure into more extended or stretched state, and the increase of random coil structures for proteins derived from wheat and rice would lead to these looser structures in the extrudates. Thus, TGase can be combined with high-moisture extrusion to regulate the formation of plant protein fibrous structures, dependent on the specific protein source and content.

Effect of protein-starch interactions on starch retrogradation and implications for food product quality

Starch retrogradation is a consequential part of food processing that greatly impacts the texture and acceptability of products containing both starch and proteins, but the effect of proteins on starch retrogradation has only recently been explored. With the increased popularity of plant-based proteins in recent years, incorporation of proteins into starch-based products is more commonplace. These formulation changes may have unforeseen effects on ingredient functionality and sensory outcomes of starch-containing products during storage, which makes the investigation of protein-starch interactions and subsequent impact on starch retrogradation and product quality essential. Protein can inhibit or promote starch retrogradation based on its exposed residues. Charged residues promote charge-dipole interactions between starch-bound phosphate and protein, hydrophobic groups restrict amylose release and reassociation, while hydrophilic groups impact water/molecular mobility. Covalent bonds (disulfide linkages) formed between proteins may enhance starch retrogradation, while glycosidic bonds formed between starch and protein during high-temperature processing may limit starch retrogradation. With these protein-starch interactions in mind, products can be formulated with proteins that enhance or delay textural changes in starch-containing products. Future work to understand the impact of starch-protein interactions on retrogradation should focus on integrating the fields of proteomics and carbohydrate chemistry. This interdisciplinary approach should result in better methods to characterize mechanisms of interaction between starch and proteins to optimize their food applications. This review provides useful interpretations of current literature characterizing the mechanistic effect of protein on starch retrogradation.

Understanding effects of glutelin on physicochemical and structural properties of extruded starch and the underlying mechanism

This work studied effects of different amounts of rice glutelin (RG) on physicochemical and structural properties of extruded rice starch (ERS) and explored the underlying mechanism of interaction between rice starch and RG upon extrusion processing. The results showed that the addition of RG altered the pasting properties, improved the viscoelastic, and increased the water mobility of ERS. The weight loss of ERS decreased from 71.40 % to 62.61 %, while the degradation temperature increased from 290.48 °C to 296.25 °C as the RG content increased from 0 % to 12 %. The complex index of extruded starch-glutelin complexes significantly elevated from 10.40 % to 35.81 % when RG content increased from 6 % to 12 %. Fourier-transform infrared spectra confirmed that RG interacted with starch via Maillard reactions, and the binding strength between RG and starch was enhanced at a higher RG content. Furthermore, results of rheological property and chemical interactions demonstrated that hydrogen bonding, hydrophobic, and electrostatic interaction were formed between RG and starch during extrusion. In summary, the obtained results of this study can further enrich the theory of starch-protein interactions and show the possibility of RG applied in the extruded starchy foods.

Conformational changes and physicochemical attributes of texturized pea protein isolate-konjac gum: With a new perspective of residence time during extrusion

The present study aimed to investigate the effects of different extrusion temperatures (110, 130 and 150 °C) and konjac gum addition (0.1 %, 0.2 %, and 0.3 %) on the flow behavior, physicochemical properties and microstructure of extruded pea protein isolate (PPI). The results showed that the textured protein could be improved by enhancing the extrusion temperature and adding konjac gum during extrusion. The water/oil holding capacity of PPI decreased and the SH content increased after extrusion. With temperature and konjac gum content increased, the β-sheet of extruded proteins transformed to other secondary structural components, and Trp residue transformed to a more polar environment, illustrating the changes in protein conformation. All extruded samples presented as yellow hue with little green and higher lightness, while excessive extrusion process reduced the brightness and promoted more formation of browning pigments. Extruded protein showed more associated layered with some air pores, and its hardness and chewiness increased with the increase of temperature and konjac gum concentration. Cluster analysis showed that the addition of konjac gum could effectively improve the quality characteristics of pea protein under low temperature extrusion, and the effect was similar to that of high temperature extrusion product. With the increase of konjac gum concentration, the flow pattern of protein extrusion gradually converted from plug flow to mixing flow, and the disorder degree of polysaccharide protein mixing system was enhanced. Moreover, Yeh-jaw model showed better fitting effect in F(θ) curves compared to Wolf-white.

Recent Advances in the Processing and Manufacturing of Plant-Based Meat

Plant protein technology is a core area of biotechnology to ease the problem of human protein demand. Plant-based meat based on plant protein technology is a growing concern by global consumers in alleviating environmental pollution, cutting down resources consumption, and improving animal welfare. Plant-based meat simulates the texture, taste, and appearance of animal meat by using protein, lipid, carbohydrate, and other plant nutrients as the main substances. This review summarizes the main components of plant-based meat, processing technology, standard formula, market competition, and formula and texture of future research directions. According to the existing methods of plant-based meat fiber forming, the development process and characteristics of four production processes and equipment of plant-based meat spinning, extrusion, shearing, and 3D printing are emphatically expounded. The processing principles and methods of different processing technologies in plant-based meat production are summarized. The production process and equipment of plant-based meat will pay more attention to the joint production of various processes to improve the defects of plant-based meat production process.

Effect of extrusion parameters on the interaction between rice starch and glutelin in the preparation of reconstituted rice

Reconstituted rice produced by extrusion has been attracted attention due to nutritional fortification and convenient production. Nevertheless, how to achieve desirable qualities and physicochemical properties of reconstituted rice nearly to natural rice by regulating extrusion process parameters is difficult. Herein, rice starch/glutelin mixture as raw material of reconstituted rice was extruded at varying extrusion conditions. Specific mechanical energy (SME) and sectional expansion index (SEI) dropped with rise in density (R² = 0.9117 and 0.8207). Solubility was enhanced with increase in product temperature (R² = 0.9085), color darkened and shifted to reddish and yellowish as extrusion temperature increased (R² = 0.8577). These trends were well fitted by sigmoid models. Furthermore, SME enhanced hydrophobic and electrostatic interactions between rice starch and glutelin and caused the reduction in crystallinity and thermal stability, promoting the formation of a bi-continuous matrix of protein aggregates with rice starch. The obtained results can be applied to guide the production of reconstituted rice with desirable qualities.

High-moisture extrusion cooking on soybean-wheat protein mixtures: Effect of sodium alginate/xanthan gum/maltodextrin on promoting a fibrous structure

At present, the changes in fibrous structure of plant proteins improved by polysaccharides during high-moisture extrusion cooking (HMEC) are still unclear. In this study, different additions (1, 2, 3, 4, and 5%) of sodium alginate (SA), xanthan gum (XG), and maltodextrin (MD) were used in the preparation of organised protein products based on soybean protein and wheat protein under high moisture extrusion conditions. It was revealed that SA-4%, XG-2%, and MD-2% (w/w) significantly enhanced the structural and physical properties of the fibres. The polysaccharides increased the water distribution of extrudates by enhancing protein-water interactions through hydrogen bonding, with MD-2% having the strongest ability to trap free water. The mechanism by which the polysaccharides improved the fibrous structure of extrudates involved the reorganization of molten proteins from the die head region to the cooling region, formation of new molecular bonds and enhancement of thermal stability. XG-2% significantly increased the β-sheet structure in the molten region (48.9 ± 1.35%) and showed the best thermal stability. Overall, SA-4% was able to better maintain the molecular bonding transformation and strong water absorption, which stabilised the protein conformation and formed the highest fibrous degree (2.1 ± 0.03). This suggests that the properties of the three polysaccharides can be used as modifiers of high water extruded plant proteins to improve the extruded materiality, functional and nutritional properties.

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.

Effects of Different Gluten Proteins on Starch’s Structural and Physicochemical Properties during Heating and Their Molecular Interactions

Starch–gluten interactions are affected by biopolymer type and processing. However, the differentiation mechanisms for gluten–starch interactions during heating have not been illuminated. The effects of glutens from two different wheat flours (a weak-gluten (Yangmai 22, Y22) and a medium-strong gluten (Yangmai 16, Y16)) on starch’s (S) structural and physicochemical properties during heating and their molecular interactions were investigated in this study. The results showed that gluten hindered the gelatinization and swelling of starch during heating when temperature was below 75 °C, due to competitive hydration and physical barriers of glutens, especially in Y22. Thus, over-heating caused the long-range molecular order and amylopectin branches of starch to be better preserved in the Y22-starch mixture (Y22-S) than in the Y16-starch mixture (Y16-S). Meanwhile, the starch’s degradation pattern during heating in turn influenced the polymerization of both glutens. During heating, residual amylopectin branching points restricted the aggregation and cross-linking of gluten proteins due to steric hindrance. More intense interaction between Y16 and starch during heating mitigated the steric hindrance in starch–gluten networks, which was due to more residual short-range ordered starch and hydrogen bonds involved in the formation of starch–gluten networks in Y16-S during heating.

Twin-Screw Extrusion of Oat: Evolutions of Rheological Behavior, Thermal Properties and Structures of Extruded Oat in Different Extrusion Zones

Further investigation of material properties during the extrusion process is essential to achieve precise control of the quality of the extrudate. Whole oat flour was used to produce low moisture puffed samples by a twin-screw extruder. X-ray diffraction (XRD), Scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermal analysis, and rheological experiments were used to deeply characterize changes in the structure and cross-linking of oats in different extrusion zones. Results indicated that the melting region was the main region that changed oat starch, including the major transformation of oat starch crystal morphology and the significant decrease of enthalpy representing the starch pasting peak in the differential scanning calorimeter (DSC) pattern (p < 0.05). Moreover, the unstable structure of the protein increased in the barrel and then decreased significantly (p < 0.05) after being extruded through the die head. The viscosity of oats increased in the cooking zone but decreased after the melting zone. A transformation occurred from elastic-dominant behavior to viscoelastic-dominant behavior for oats in the melting zone and after being extruded. This study provides further theoretical support for the research of the change of materials during extrusion and the development of oat-based food.

Effective Use of Plant Proteins for the Development of "New" Foods

Diversity in our diet mirrors modern society. Affluent lifestyles and extended longevity have caused the prevalence of diabetes and sarcopenia, which has led to the increased demand of low-carb, high-protein foods. Expansion of the global population and Westernization of Asian diets have surged the number of meat eaters, which has eventually disrupted the supply–demand balance of meat. In contrast, some people do not eat meat for religious reasons or due to veganism. With these multiple circumstances, our society has begun to resort to obtaining protein from plant sources rather than animal origins. This “protein shift” urges food researchers to develop high-quality foods based on plant proteins. Meanwhile, patients with food allergies, especially gluten-related ones, are reported to be increasing. Additionally, growing popularity of the gluten-free diet demands development of foods without using ingredients of wheat origin. Besides, consumers prefer “clean-label” products in which products are expected to contain fewer artificial compounds. These diversified demands on foods have spurred the development of “new” foods in view of food-processing technologies as well as selection of the primary ingredients. In this short review, examples of foodstuffs that have achieved tremendous recent progress are introduced: effective use of plant protein realized low-carb, high protein, gluten-free bread/pasta. Basic manufacturing principles of plant-based vegan cheese have also been established. We will also discuss on the strategy of effective development of new foods in view of the better communication with consumers as well as efficient use of plant proteins.