Effects of Mesona chinensis polysaccharide on the thermostability, gelling properties, and molecular forces of whey protein isolate gels

Effects of konjac glucomannan with different degrees of deacetylation on the properties and structure of wheat gluten protein

The properties and structure of gluten protein with different deacetylation degrees of konjac glucomannan (KGM) were investigated, in an attempt to improve the quality of gluten protein in flour products. Results showed that deacetylated KGM (DKGM) could improve the textural properties and enhance the thermal stability of gluten protein. DKGM increased the water holding capacity and shortened the T2 relaxation time of gluten after removing some acetyl groups. As the deacetylation degree increased, the hardness and adhesiveness of gluten gels gradually increased, while the springiness decreased. In addition, the presence of DKGM promoted the conversion from free sulfhydryl to disulfide bonds and increased the β-sheet content in gluten protein. The low-deacetylation KGM decreased the surface hydrophobicity and fluorescence intensity of gluten protein, and the microstructures of gluten gels became more compact. Compared with gluten protein-KGM complex gel, the degradation temperature of gluten protein-DKGM complex gels was observed to increase by >3 °C. Overall, the low-deacetylation KGM was beneficial for improving the physicochemical properties and maintaining the network structure of gluten protein. This study provides valuable references and practical insights to improve gluten quality in the flour industry.

Effect of pH on the soybean whey protein-gum arabic emulsion delivery systems for curcumin: Emulsifying, stability, and digestive properties

A novel curcumin (CUR) delivery system was developed using soybean whey protein (SWP)-based emulsions, enhanced by pH-adjustment and gum arabic (GA) modification. Modulating electrostatic interactions between SWP and GA at oil/water interface, pH provides favorable charging conditions for stable distribution between droplets. GA facilitated the SWP form a stable interfacial layer that significantly enhanced the emulsifying properties and CUR encapsulation efficiency of the system at pH 6.0, which were 90.15 ± 0.67%, 870.53 ± 3.22 m2/g and 2157.62 ± 115.31%, respectively. Duncan's test revealed significant improvements in thermal, UV, oxidative, and storage stabilities of CUR (P < 0.05). At pH 6.0, GA effectively protected CUR by inhibiting SWP degradation during gastric digestion and promoting the release of CUR by decreasing steric hindrance with oil droplets during intestinal digestion, achieving the highest CUR bioaccessibility (69.12% ± 0.28%) based on Duncan's test. The SWP-GA-CUR emulsion delivery system would be a novel carrier for nutrients.

Salt ions improve soybean protein isolate/curdlan complex fat substitutes: Effect of molecular interactions on freeze-thaw stability

Although emulsion gels show significant potential as fat substitutes, they are vulnerable to degreasing, delamination, and other undesirable processes during freezing, storage, and thawing, leading to commercial value loss in terms of juiciness, flavor, and texture. This study investigated the gel strength and freeze-thaw stability of soybean protein isolate (SPI)/curdlan (CL) composite emulsion gels after adding sodium chloride (NaCl). Analysis revealed that adding low salt ion concentrations promoted the hardness and water-holding capacity (WHC) of fat substitutes, while high levels displayed an inhibitory effect. With 40 mM NaCl as the optimum concentration, the hardness increased from 259.33 g (0 mM) to 418.67 g, the WHC increased from 90.59 % to 93.18 %, exhibiting good freeze-thaw stability. Confocal laser scanning microscopy (CLSM) and particle size distribution were used to examine the impact of salt ion concentrations on protein particle aggregation and the damaging effect of freezing and thawing on the proteoglycan complex network structure. Fourier-transform infrared spectroscopy (FTIR) and protein solubility evaluation indicated that the composite gel network structure consisted of covalent contacts between the proteoglycan molecules and hydrogen bonds, playing a predominant role in non-covalent interaction. This study showed that the salt ion concentration in the emulsion gel affected its molecular interactions.

Preparation technologies, structural features, and biological activities of polysaccharides from Mesona chinensis Benth.: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Mesona chinensis Benth. (or Platostoma palustre (Blume) A. J. Paton) is an important medicinal and edible plant also known as the Hsian-tsao in China and Southeast Asian countries. It is cold in nature and sweet in taste, with the effects of clearing heat, relieving heatstroke and diuretic, and traditionally used to treat heatstroke, erysipelas, hypertension, joint pain and other diseases in folk medicine. It is also a popular supplement with the function of detoxifying and heat-clearing use in Asia. It is used to be processed into the popular tea, Bean jelly, and so on. Published studies have demonstrated that polysaccharides from M. chinensis (MCPs) are one of the principal bioactive ingredients with a variety of health-promoting effects in the prevention and treatment of diseases, including antioxidant, immunomodulation, anti-inflammatory, hepatoprotective, anti-tumor, hypoglycemic, regulation of gut microbiota, and other pharmacological properties.

AIM OF THE REVIEW

This review aims to compile the extraction and purification methods, structural characteristics, pharmacological activities including the mechanism of action of MCPs, and to further understand the applications of M. chinensis in order to lay the foundation for the development of MCPs.

MATERIALS AND METHODS

By inputting the search term "Mesona chinensis polysaccharides", relevant research information was obtained from databases such as PubMed, Google Scholar, Web of Science, and China National Knowledge Infrastructure (CNKI).

RESULTS

More than 40 polysaccharides have been extracted from M. chinensis, different extraction and purification methods have been described, as well as the structural features and pharmacological activities of MCPs have been systematically reviewed. Polysaccharides, as important components of M. chinensis, were mainly extracted by methods such as hot water dipping method, hot alkali extraction method, enzyme-assisted extraction method and ultrasonic-assisted extraction method, subsequently obtained by decolorization, deproteinization, removal of other small molecules and separation on various chromatographic columns. The chemical composition and structure of MCPs show diversity and have a variety of pharmacological activities, including antioxidant, immunomodulation, anti-inflammatory, hepatoprotective, anti-tumor, hypoglycemic, regulation of gut microbiota, and so on.

CONCLUSIONS

This article systematically reviews the research progress of MCPs in terms of extraction and purification, structural characteristics, rheological gel properties, pharmacological properties, and safety assessment. The potentials and roles of M. chinensis in the field of medicine, functional food, and materials are further highlighted to provide references and bases for the high-value processing and utilization of MCPs.

Effects and mechanisms of different κ-carrageenan incorporation forms and ionic strength on the physicochemical and gelling properties of myofibrillar protein

The present work was aimed to investigate the effects of incorporating κ-carrageenan into myofibrillar protein (MP) as a dry powder (CP) or water suspension (CW) and the ionic strength (0.3 or 0.6 M sodium chloride (NaCl)) on MP physicochemical and gelling properties. The results indicated that incorporation of either CP or CW significantly increased turbidity, surface hydrophobicity, particle size and rheological behaviour of MP. In contrast, the protein solubility and fluorescence intensity of MP decreased when added with each form of κ-carrageenan (P < 0.05). These observed effects improved MP's gelling properties and produced a more compact and homogenous gel network after heating treatment. Moreover, the addition of CW rendered higher gel strength, water holding capacity and intermolecular interactions, such as ionic, hydrogen and disulphide bonds and hydrophobic interactions in MP gel compared with those added with CP, especially for 0.3 M NaCl (P < 0.05). Furthermore, addition of CW significantly decreased the α-helix content of MP gels (P < 0.05), which mainly contributing to the transformation from a random structure to an organised configuration. In addition, a higher NaCl concentration (0.6 M) enhanced the gelling properties of MP gels compared with 0.3 M NaCl concentration in the presence of each form of κ-carrageenan. Therefore, our present study indicated that incorporation form of κ-carrageenan and ionic strength have distinctive effects on regulating physicochemical characteristics and improves gelling properties of MP.

Characterization of fruit pulp-soy protein isolate (SPI) complexes: Effect of superfine grinding

Superfine grinding (SG), as an innovative technology, was conducted to improve the physicochemical and structural properties of fruit pulps. Nectarine, apple, and honey peach were selected as the materials. With the increase in SG frequency, the soluble solids content, viscosity, D[4, 3], D[3, 2], G' and G″ of fruit pulps were evidently decreased, whereas the turbidity was increased. The smallest D[4, 3] (294.90 µm) and D[3, 2] (159.67 µm) were observed in nectarine pulp under SG at 50 Hz. The highest turbidity (266.33) was shown in honey peach pulp under SG at 50 Hz. The active groups of the fruit pulps with SG were exposed by Fourier transform infrared spectroscopy (FT-IR). Notably, the excessive destruction in structure was confirmed in SG with 50 Hz. With soy protein isolate (SPI) addition, D[4, 3] and D[3, 2] of complexes decreased, whereas G' and G″ increased. The formation of new fruit pulp-SPI complexes was demonstrated by FT-IR and LF-NMR analysis. The dense and uniform structure was found in complexes prepared by SPI and fruit pulp with 30 Hz SG. Especially, apple-SPI complex with 30 Hz SG showed the highest water-holding capacity (WHC) (0.75) and adhesiveness (7973.00 g s). A significant correlation between fruit pulps and the complexes was revealed. Taken together, the impact of SG modification on fruit pulps would enhance WHC, rheology, and textural properties of the fruit pulp-SPI complexes, especially for SG with 30 Hz. PRACTICAL APPLICATION: This research provided a comprehensive exploration of the potential of SG technology to modify fruit pulps, solving the diversity of textural customization problems and offering valuable insights for the development of semisolid food products.

Wheat bran arabinoxylan-soybean protein isolate emulsion-filled gels as a β-carotene delivery carrier: Effect of polysaccharide content on textural and rheological properties

This study aimed to investigate the effects of different wheat bran arabinoxylan (WBAX) concentrations (1, 2, 3, and 4 wt%) on the structural and physicochemical properties of WBAX-soybean protein isolate (SPI) emulsion-filled gels (EFGs) prepared using laccase and heat treatment. The properties of the various gels as well as their microstructure, rheology, and in vitro digestion behaviors were investigated. Results showed that WBAX-SPI EFGs with a 3 wt% WBAX concentration had a smooth and uniform appearance, high water holding capacity (98.5 ± 0.2 %), and enhanced mechanical properties. Rheological experiments suggested that a stronger and closer gel network was formed at 3 wt% WBAX concentration. Fourier transform infrared spectroscopy showed that laccase and heat treatment not only catalyzed the intramolecular crosslinking of WBAX and SPI, respectively, but also promoted the interaction between WBAX and SPI. Confocal laser scanning microscopy revealed that the WBAX gel network was interspersed within the SPI network. The interactions contributing to the gelation analysis revealed that chemical (disulfide bond) and physical (hydrogen bond and hydrophobic) interactions promoted the formation of denser EFGs. Furthermore, the WBAX-SPI EFGs provided a β-carotene bioaccessibility of 21.8 ± 0.6 %. Therefore, our study suggests that WBAX-SPI EFGs hold promising potential for industrial applications in the delivery of β-carotene.

Development of arachin and basil seed gum composite gels for the encapsulation and controlled release of vitamin D3

In this study, the textural and rheological properties of arachin and basil seed gum composite gels (ABG) were successfully regulated by the addition of sodium chloride (NaCl) and transglutaminase (TGase). The texture profile analysis (TPA) results showed that the hardness and springiness of the ABG were significantly enhanced by adding TGase (p < 0.05). Particularly, the composite gel added with NaCl first and subsequently crosslinked by TGase (ABG-Na+-TG) showed a higher hardness value of 186.0 ± 6.1 g. ABG-Na+-TG showed a higher amplitude of strain with lower compliance in the creep and recovery test and exhibited a better elastic behavior. These composite gels were employed as new delivery systems to encapsulate and deliver vitamin D3 (VD3). ABG-Na+-TG showed a higher VD3 encapsulation efficiency of 91.7 % and a better protection of VD3 under different temperatures or UV light, as well as an improved storage stability of VD3. Furthermore, the release of VD3 in the simulated gastric digestion could be controlled by ABG-Na+-TG and the bioaccessibility after digestion was 32.9 %. These results suggest that ABG-Na+-TG can be utilized as a promising delivery system of VD3.

Antioxidant stability and in vitro digestion of β-carotene-loaded oil-in-water emulsions stabilized by whey protein isolate-Mesona chinensis polysaccharide conjugates

The aim of this study was to investigate the delivery of functional factor β-carotene by emulsion stabilized with whey protein isolate-Mesona chinensis polysaccharide (WPI-MCP) conjugate. Results showed that the WPI-MCP complex had better antioxidant properties than WPI. Correspondingly, the emulsions stabilized by this complex also had better oxidative stability compared with protein emulsions alone. The particle size of WPI-MCP emulsion was smaller and had a better stability when MCP was added at 0.2 % (w/v). The sizes of WPI-MCP and WPI emulsions were 3594.33 and 7765.67 nm at pH 4, indicating improved emulsion stability around isoelectric point of WPI. At different NaCl concentrations, the absolute values of zeta-potential of WPI-MCP emulsions were larger than that of WPI emulsions except 0.1 % (mol/L) NaCl. The sizes of WPI and WPI-MCP emulsions were 2384.32 and 790.12 nm, respectively. During in vitro digestion, WPI-MCP stabilized emulsions slowed down the release of free fatty acids and achieved about 80 % bioaccessibility of β-carotene, indicating that WPI-MCP-stabilized emulsions encapsulating β-carotene can effectively control the release of bioactive substances. These studies have potential significance and value for the construction of food-grade emulsion delivery system.

Modification of low-salt myofibrillar protein using combined ultrasound pre-treatment and konjac glucomannan for improving gelling properties: Intermolecular interaction and filling effect

The quality deterioration of low-salt meat products has been gained ongoing focus of researchers. In this study, konjac glucomannan (KGM) was used to alleviate the finiteness of ultrasound treatment on the quality improvement of low-salt myofibrillar protein (MP), and the modification sequence was also investigated. The results revealed that the single and double sequential modification by utilizing KGM and ultrasound significantly influenced the gelation behavior of low-salt MPs. The uniform MP-KGM mixture formed by a single ultrasound treatment had limited protein unfolding, resulting in relatively weak intermolecular forces in the composite gel. Importantly, ultrasound pre-treatment combined with KGM modification promoted the unfolding and moderate thermal aggregation of proteins and remarkably improved the rheological behaviors and gel strength of the composite gel. This result could also be corroborated by the highest percentage of trans-gauche-trans conformation of SS bridges and maximum β-sheet proportion. Furthermore, molecular dynamic simulation and molecular docking elucidated that the hydrogen bond length between protein and KGM was shortened after ultrasound pre-treatment, which was the molecular basis for the enhanced intermolecular interactions. Therefore, ultrasound pre-treatment combined with KGM can effectively improve the gelling properties of low-salt MPs, providing a practical method for the processing of low-salt meat products.

Synergistic effects of oxidized konjac glucomannan on rheological, thermal and structural properties of gluten protein

Oxidation is an effective way to prepare depolymerized konjac glucomannan (KGM). The oxidized KGM (OKGM) differed from native KGM in physicochemical properties due to different molecular structure. In this study, the effects of OKGM on the properties of gluten protein were investigated and compared with native KGM (NKGM) and enzymatic hydrolysis KGM (EKGM). Results showed that the OKGM with a low molecular weight and viscosity could improve rheological properties and enhance thermal stability. Compared to native gluten protein (NGP), OKGM stabilized the protein secondary structure by increasing the contents of β-sheet and α-helix, and improved the tertiary structure through increasing the disulfide bonds. The compact holes with shrunk pore size confirmed a stronger interaction between OKGM and gluten protein through scanning electron microscopy, forming a highly networked gluten structure. Furthermore, OKGM depolymerized by the moderate ozone-microwave treatment of 40 min had a higher effect on gluten proteins than that by the 100 min treatment, demonstrating that the excessive degradation of KGM weakened the interaction between the gluten protein and OKGM. These findings demonstrated that incorporating moderately oxidized KGM into gluten protein was an effective strategy to improve the properties of gluten protein.

Biosynthesis and physicochemical properties of low molecular weight gellan produced by a high-yield mutant of Sphingomonas paucimobilis ATCC 31461

Gellan gum (GG) is used in many industries. Here, we obtained a low molecular weight GG (L-GG) directly produced by M155, the high-yield mutant strain of Sphingomonas paucimobilis ATCC 31461, which was selected using UV-ARTP combined mutagenesis. The molecular weight of L-GG was 44.6 % lesser than that of the initial GG (I-GG), and the GG yield increased by 24 %. The monosaccharide composition and Fourier transform-infrared spectroscopic patterns of L-GG were similar to those of I-GG, which indicated that the decrease in the molecular weight of L-GG was probably because of reduction in the degree of polymerization. In addition, microstructural analysis revealed that the surface of L-GG was rougher, with smaller pores and tighter network, than that of I-GG. L-GG showed low hardness, gumminess, and chewiness, which are indicative of better taste. The results of rheological analysis revealed that the L-GG solution is a typical non-Newtonian fluid with low viscoelasticity, which exhibited stable dynamic viscoelasticity within 20-65 °C. To the best of our knowledge, this is the first report of direct biosynthesis of low molecular weight GG during fermentation, which will reduce the manufacturing costs. Our observations provide a reference for precise and expanded applications of GG.

Carboxymethylation modification, characterization of dandelion root polysaccharide and its effects on gel properties and microstructure of whey protein isolate

In the present study, a native polysaccharide (DP) with sugar content of 87.54 ± 2.01 % was isolated from dandelion roots. DP was chemically modified to obtain a carboxymethylated polysaccharide (CMDP) with DS of 0.42 ± 0.07. DP and CMDP were composed of the same six monosaccharides including mannose, rhamnose, galacturonic acid, glucose, galactose, and arabinose. The molecular weights of DP and CMDP were 108,200 and 69,800 Da, respectively. CMDP exhibited more stable thermal performance and better gelling properties than DP. The effects of DP and CMDP on the strength, water holding capacity (WHC), microstructure, and rheological properties of whey protein isolate (WPI) gels were investigated. Results showed that CMDP-WPI gels had higher strength and WHC than DP-WPI gels. With the addition of 1.5 % CMDP, WPI gel had a good three-dimensional network structure. The apparent viscosities, loss modulus (G"), and storage modulus (G') of WPI gels were increased with the polysaccharide addition, the influence of CMDP was remarkable compared to DP at the same concentration. These findings suggest that CMDP may be used as a functional ingredient in protein-containing food products.

Impact of Insoluble Dietary Fiber and CaCl2 on Structural Properties of Soybean Protein Isolate-Wheat Gluten Composite Gel

The effect and mechanism of soybean insoluble dietary fiber (SIDF) (0~4%) and CaCl₂ (0~0.005 M) on the properties of soybean protein isolate (SPI)-wheat gluten (WG) composite gel were studied. It was revealed that the addition of insoluble dietary fiber (1~2%) increased the strength and water-holding capacity (WHC) of the composite gel (p < 0.05) and enhanced the gel network structure compared with the control. WHC and LF-NMR showed that the water-binding ability of the gel system with only 2% SIDF was the strongest. The addition of excessive SIDF increased the distance between protein molecules, impeded the cross-linking of protein, and formed a three-dimensional network with low gel strength. The infrared spectrum and intermolecular force indicated that the interaction between SIDF and SPI were mainly physical, and the hydrophobic interaction and disulfide bond were the main forces in the gel system. The addition of CaCl₂ can increase the critical content of gel texture destruction caused by SIDF, and the gel strength attained its peak at 3% SIDF, indicating that appropriate CaCl₂ improved gel structure weakening caused by excessive SIDF. This study provides insights in enhancing the production of multi-component composite gel systems.

The effect of sweet tea polysaccharide on the physicochemical and structural properties of whey protein isolate gels

In this study, we investigated the effect of sweet tea polysaccharide (STP) on the physicochemical and structural properties of heat-induced whey protein isolate (WPI) gels, and explored the potential mechanism. The results indicated that STP promoted the unfolding and cross-linking of WPI to form a stable three-dimensional network structure, and significantly improved the strength, water-holding capacity and viscoelasticity of WPI gels. However, the addition of STP was limited to 2 %, too much STP would loosen the gel network and affect the gel properties. The results of FTIR and fluorescence spectroscopy suggested that STP affected the secondary and tertiary structures of WPI, promoted the movement of aromatic amino acids to the protein surface and the conversion of α-helix to β-sheet. In addition, STP reduced the surface hydrophobicity of the gel, increased the free sulfhydryl content, and enhanced the hydrogen bonding, disulfide bonding, and hydrophobic interactions between protein molecules. These findings can provide a reference for the application of STP as a gel modifier in the food industry.

Reversibility of freeze-thaw/re-emulsification on Pickering emulsion stabilized with gliadin/sodium caseinate nanoparticles and konjac glucomannan

The reversibility of freeze-thaw/re-emulsification of Pickering emulsion stabilized by gliadin/sodium caseinate nanoparticles (Gli/CAS NPs) was improved by adding konjac glucomannan (KGM). With the increase in the KGM concentration, the delamination of emulsions after freeze-thaw treatment was significantly improved. The microstructure showed that the presence of KGM helped to maintain the network structure of continuous phases. In particular, the particle size of the emulsion did not increase significantly after three freeze-thaw cycles when the KGM concentration was 0.6 % and the oil phase fraction was 60 %. The results of flocculation degree and coalescence degree also indicated that KGM promoted the cross-linking between particles on the surface of the droplet and increased the thickness of the interfacial film of the droplet. Rheological analysis also proved the same result: the elastic modulus of the emulsion was still larger than the viscous modulus, which showed the ideal freeze thaw reversibility. After adding KGM, the emulsion formed a strong network structure with good stability for long-term storage and reversibility for freeze-thaw cycling/re-emulsification. Thus, the emulsion has broad application prospects in food, cosmetics, and pharmaceutical fields.

Influence of rose anthocyanin extracts on physicochemical properties and in vitro digestibility of whey protein isolate sol/gel: Based on different pHs and protein concentrations

Protein-polyphenol interactions can improve the physicochemical properties of proteins. The objective of this study was to investigate the influence of rose anthocyanin extracts (RAEs) on the physicochemical properties and digestibility of whey protein isolate (WPI) sol/gel at different pHs and protein concentrations. Hydrophobicity interaction and ionic bonding were the main forces for the formation of acidic WPI and WPI-RAEs sol/gel. When pH was higher than 2.4, sol/gel became unstable, which may be related to hydrophobicity, ζ-potential value, total sulfhydryl and free sulfhydryl content changes. In addition, RAEs had positive effects on the color and water distribution of all WPI sol/gel. Moreover, RAEs improved the viscoelasticity of WPI sol/gel with protein content ≥ 12 % (w/v) at pH 2.4. More importantly, the addition of RAEs could reduce the digestibility of WPI sol/gel. We hope our works can provide promising strategies for developing WPI-RAEs foods.

Properties of whey protein isolation/konjac glucomannan composite gels: Effects of deacetylation degrees

The effects of konjac glucomannan (KGM) with different deacetylation degrees (DDs) on the gel properties of whey protein isolate (WPI) were investigated. The appropriately deacetylated KGM (DDs in the range of 0-53.85 %) incorporated within WPI and formed relatively uniform compound gels, while excessive deacetylated KGM (DDs = 63.46 or 71.63 %) caused macroscopic precipitation and aggregation in WPI-KGM system. The water holding capacity of WPI-KGM gels decreased with the gradual increase of DDs, and the removal of acetyl groups reduced the whiteness of the composite gels. The hardness and chewiness of the composite gel tended to increase and subsequently decrease with the enhancement of DDs, and reached the maximum (244.15 and 148.88 g, respectively) at the DDs of 53.85 %. The rheological analysis indicated that rigid structured WPI-KGM gels could be formed when incorporated with moderately deacetylated KGM. The deacetylated KGM (DDs = 53.85 %) enhanced the hydrogen bond and disulfide bond within the mixed system, resulting in a more compact network structure of the composite gels. Moreover, deacetylated KGM particles might also reinforce the gel strength by the "filling effects". Overall, the gelation characteristics of the WPI-KGM system can be regulated by controlling the DDs of KGM.

Whey Protein Isolate-Mesona chinensis Polysaccharide Conjugate: Characterization and Its Applications in O/W Emulsions

Mesona chinensis polysaccharide (MCP), a common thickener, stabilizer and gelling agent in food and pharmaceuticals, also has antioxidant, immunomodulatory and hypoglycemic properties. Whey protein isolate (WPI)-MCP conjugate was prepared and used as a stabilizer for O/W emulsion in this study. FT-IR and surface hydrophobicity results showed there could exist interactions between -COO- in MCP and -NH³⁺ in WPI, and hydrogen bonding may be involved in the covalent binding process. The red-shifted peaks in the FT-IR spectra suggested the formation of WPI-MCP conjugate, and MCP may be bound to the hydrophobic area of WPI with decreasing surface hydrophobicity. According to chemical bond measurement, hydrophobic interaction, hydrogen bond and disulfide bond played the main role in the formation process of WPI-MCP conjugate. According to morphological analysis, the O/W emulsion formed by WPI-MCP had a larger size than the emulsion formed by WPI. The conjugation of MCP with WPI improved the apparent viscosity and gel structure of emulsions, which was concentration-dependent. The oxidative stability of the WPI-MCP emulsion was higher than that of the WPI emulsion. However, the protection effect of WPI-MCP emulsion on β-carotene still needs to be further improved.

Walnut Protein Isolate-κ-Carrageenan Composite Gels Improved with Synergetic Ultrasound-Transglutaminase: Gelation Properties and Structure

Walnut protein is a kind of natural, high-quality plant protein resource. However, its high content of gluten, strong hydrophobicity and poor gelation ability have greatly limited its development and utilization in gel products. It was found in this experiment that ultrasonic power combined with transglutaminase (TGase) had a significant effect on the gel properties of the walnut protein isolate (WNPI)-κ-carrageenan (KC) complex. The results showed that the gel strength of the WNPI-KC complex first increased and then decreased with the increase in ultrasonic power (0-400 W). WNPI-KC composite gel had the best texture properties, rheological properties, water-holding capacity (99.41 ± 0.76%), swelling ratio (2.31 ± 0.29%) and thermal stability (83.22 °C) following 200 W ultrasonic pretreatment. At this time, the gel network was more uniform and much denser, and the water molecules were more tightly bound. Further, 200 W ultrasonic pretreatment could promote the transformation of α-helices to β-folds in protein molecules, improve the fluorescence intensity, increase the content of free sulfhydryl groups and enhance the intermolecular forces. The experimental results could provide technical support for the development of walnut protein gel food.

Development, characterization and probiotic encapsulating ability of novel Momordica charantia bioactive polysaccharides/whey protein isolate composite gels

In this study, a polysaccharide (MP1) with a molecular weight of 38 kDa was isolated from Momordica charantia which contains arabinose, galactose, xylose, and rhamnose. (MP1) was used to formulate composite gels with Whey Protein Isolate (WPI) that were characterized for their functional properties, microstructure, thermal resistance, probiotic encapsulating ability, and potential toward metabolic syndrome (MS). Results showed that the highest complex index was obtained at MP concentration of 2 %. MP-WPIs demonstrated superior (p < 0.05) water holding capacity and emulsifying properties than WPI gels. MP-WPIs also had higher (p < 0.05) thermal stability via TGA and DSC analysis. MP-WPI morphology was observed via SEM whereas protein structure as affected by MP concentration was studied using CLSM. Also, FTIR revealed that MP and WPI bonded mainly through electrostatic, hydrophobic and hydrogen interactions. More, MP-WPIs successfully enhanced probiotic Lactobacillus acidophilus (LA) survival upon freeze-drying with high encapsulation efficiency (98 %) and improved storage stability. MP-WPIs improved LA survival upon digestion suggesting a potential prebiotic activity. Finally, synbiotic formulation LA-MP-WPIs exhibited effective biological activity against MS. Therefore, MP-WPIs is a propitious strategy for effective probiotic gastrointestinal delivery with potential toward MS.

Konjac glucomannan improves the gel properties of low salt myofibrillar protein through modifying protein conformation

Improving the characteristics of low salt proteins is the key to the gel properties of low-salt meat products which are demanded by people nowadays. The present study focused on the effects of KGM concentrations on the changes in structure and gelling properties of low-salt myofibrillar protein (MP). KGM addition (≤0.75 %) irrespective of salt concentration modified secondary and tertiary structures of MPs, enhanced the binding capacity of Troponin-T and Tropomyosin, augmented the gelling behavior of proteins, and remarkably improved the storage modulus (G') and gel strength of heat-induced MP gels. Interestingly, KGM addition in low salt condition showed the transformation of the all-gauche SS conformation into gauche-gauche-trans and trans-gauche-trans, and the partial transformation of α-helices into β-sheets. overall, KGM modified the structure of low salt MPs and thus improved the gel properties of low salt MPs. Therefore, KGM is recommended for low-salt meat processing to enhance the MP gelling potential.

Soy Protein Isolate/Sodium Alginate Microparticles under Different pH Conditions: Formation Mechanism and Physicochemical Properties

The effects of sodium alginate (SA) and pH value on the formation, structural properties, microscopic morphology, and physicochemical properties of soybean protein isolate (SPI)/SA microparticles were investigated. The results of ζ-potential and free sulfhydryl (SH) content showed electrostatic interactions between SPI and SA, which promoted the conversion of free SH into disulfide bonds within the protein. The surface hydrophobicity, fluorescence spectra, and Fourier transform infrared spectroscopy data suggested that the secondary structure and microenvironment of the internal hydrophobic groups of the protein in the SPI/SA microparticles were changed. Compared with SPI microparticles, the surface of SPI/SA microparticles was smoother, the degree of collapse was reduced, and the thermal stability was improved. In addition, under the condition of pH 9.0, the average particle size of SPI/SA microparticles was only 15.92 ± 0.66 μm, and the distribution was uniform. Rheological tests indicated that SA significantly increased the apparent viscosity of SPI/SA microparticles at pH 9.0. The maximum protein solubility (67.32%), foaming ability (91.53 ± 1.12%), and emulsion activity (200.29 ± 3.38 m²/g) of SPI/SA microparticles occurred at pH 9.0. The application of SPI/SA microparticles as ingredients in high-protein foods is expected to be of great significance in the food industry.

Effect and Mechanism of Acid-Induced Soy Protein Isolate Gels as Influenced by Cellulose Nanocrystals and Microcrystalline Cellulose

The effects of cellulose nanocrystals (CNC) and microcrystalline cellulose (MCC) on the gel properties and microstructure of glucono-δ-lactone-induced soy protein isolate (SPI) gels were investigated. The water-holding capacity, gel strength, and viscoelastic modulus of CNC–SPI gels were positively associated with CNC concentration from 0 to 0.75% (w/v). In contrast, MCC–SPI gels exhibited decreased water-holding capacity, gel strength, and viscoelastic modulus. All composite gels displayed high frequency dependence and the typical type I (strain thinning) network behavior. Changes in viscoelasticity under large strain were correlated with differences in the microstructure of SPI composite gels. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that CNC were more evenly and steadily distributed in the protein matrix and formed a compact network structure. In contrast, MCC–SPI gels exhibited a discontinued and rough gel network with some large aggregates and pores, in which MCC was randomly entrapped. Fourier transform infrared spectroscopy (FTIR) and molecular forces results revealed that no new chemical bonds were formed in the gelation process and that the disulfide bond was of crucial importance in the gel system. With the addition of CNC, electrostatic interactions, hydrophobic interactions, and hydrogen bonds in the SPI gel network were significantly strengthened. However, the incorporation of MCC might obstruct the connection of the protein network. It is concluded that both cellulose type and concentration affect gelling properties.

A polysaccharide from Lignosus rhinocerotis sclerotia: Self-healing properties and the effect of temperature on its rheological behavior

This work investigated the self-healing properties of Lignosus rhinocerotis polysaccharide (LRP) and the effect of temperature on its rheological behavior. Dynamic sweep tests (strain sweep, frequency sweep, and time sweep) showed that the LRP/water system possessed self-healing properties due to the entangled network formed by hyperbranched LRP molecular chains. The flow activation energy of LRP solution calculated by Arrhenius equation was shown to decrease with increasing LRP concentration, indicating that LRP solution at higher concentration was less sensitive to temperature. Temperature ramp test exhibited that LRP had a glass transition temperature (T_g) determined as 49.35 °C and the temperature effect was irreversible. Microrheological test revealed that the LRP aqueous solution can form a gel at room temperature with the concentration ≥ 20 mg/mL. This work provided a theoretical basis for the development of LRP-based self-healing materials and facilitated a deep understanding of the temperature effect on rheological behavior of LRP.

Acid/alkali shifting of Mesona chinensis polysaccharide-whey protein isolate gels: Characterization and formation mechanism

In this study, structural characteristics and formation mechanism of Mesona chinensis polysaccharide (MCP)-whey protein isolate (WPI) gels including group and molecular changes, intermolecular forces, crystallinity, and moisture migration were investigated under pH shifting conditions. Results showed that MCP and WPI formed a stable gel at pH 10. The free sulfhydryl groups and surface hydrophobicity of the MCP-WPI gels increased with the increasing pH. Hydrophobic and hydrogen bond interactions were the main molecular forces involved in the MCP-WPI gels, and electrostatic interactions and disulfide bonds played a complementary role. The pH conditions evidently influenced the secondary conformational structure of MCP-WPI gels. Molecular weight and X-ray diffraction (XRD) analysis indicated the formation of a hypocrystalline complex with molecular interaction. In addition, low-field magnetometry (LF-NMR) results showed that the T₂ values decreased with increasing pH, indicating that water and gel matrix had the highest interactions at pH 10.