Effect of sodium metabisulfite-mediated self-assembly on the quality of silver carp myofibrillar protein-EGCG composite gels.

Myofibrillar protein (MP) gels are susceptible to oxidation, which can be prevented by complexing with hydrophilic polyphenols, but may cause gel deterioration. Sodium metabisulfite (Na2S2O5) has been used to induce self-assembly of MP and analyze the impact of self-assembly on the quality of composite gels containing high amounts of (-)-epigallocatechin gallate (EGCG). Hydrophobic forces were confirmed as the main driver of self-assembly. Self-assembly reduced the size of the MP-EGCG complex to approximately 670 nm and increased the gel's hydrophobic force by approximately 3.6-fold. The maximum hardness of the Na2S2O5-treated MP-EGCG composite gel was 52.43 g/kg, which was approximately 49% greater than pure MP gel. After oxidative treatment, the Na2S2O5-treated MP-EGCG composite gel had considerably lower carbonyl and dityrosine levels (2.47-µmol/g protein and 450 a.u.) than the control (8.37-µmol/g protein and 964 a.u.). Therefore, Na2S2O5 shows potential as a cost-effective additive for alleviating MP limitations in the food industry.

Modulation of fried spring roll wrapper quality upon treatment of batter with maltogenic amylase, transglutaminase and bromelain.

BACKGROUND: Fried foods are favored for their unique crispiness, golden color and flavor, but they also face great challenge because of their high oil content, high calories and the existence of compounds such as acrylamide and polycyclic aromatic hydrocarbons. Long-term consumption of fried foods may adversely affect health. Therefore, it is necessary to explore fried foods with lower oil contents and a high quality to meet the demand. RESULTS: A method of enzyme treatment was explored to investigate the effects of maltogenic amylase (MA), transglutaminase (TG) and bromelain (BRO) on the physicochemical properties of the batter and the quality of fried spring roll wrapper (FSRW). The results showed that the MA-, TG- or BRO-treated batters had a significant shear-thinning behavior, especially with an increase in viscosity upon increasing TG contents. FSRW enhanced its fracturability from 419.19 g (Control) to 616.50 g (MA-6 U g-1), 623.49 g (TG-0.75 U g-1) and 644.96 g (BRO-10 U g-1). Meanwhile, in comparison with BRO and MA, TG-0.5 U g-1 endowed batter with the highest density and thermal stability. MA-15 U g-1 and TG-0.5 U g-1 displayed FSRW with uniform and dense pores, and significantly reduced its oil content by 18.05% and 25.02%, respectively. Moreover, compared to MA and TG, BRO-50 U g-1 improved the flavor of FSRW. CONCLUSION: MA, TG or BRO played a key role in affecting the physicochemical properties of the batter and the quality of FSRW. TG-0.5 U g-1 remarkly reduced the oil content of FSRW with a great potential in practical application. © 2024 Society of Chemical Industry.

Self-assembled pea vicilin nanoparticles as nanocarriers for improving the antioxidant activity, environmental stability and sustained-release property of curcumin.

BACKGROUND: The application of curcumin (Cur) in the food industry is usually limited by its low water solubility and poor stability. This study aimed to fabricate self-assembled nanoparticles using pea vicilin (7S) through a pH-shifting method (pH 7-pH 12-pH 7) to develop water-soluble nanocarriers of Cur. RESULTS: Intrinsic fluorescence, far-UV circular dichroism spectra and transmission electron microscopy analysis demonstrated that the structure of 7S could be unfolded at pH 12.0 and refolded when the pH shifted to 7.0. The assembled 7S-Cur exhibited a high loading ability of 81.63 µg mg-1 for Cur and homogeneous particle distribution. Cur was encapsulated in the 7S hydrophobic nucleus in an amorphous form and combined through hydrophobic interactions and hydrogen bonding, resulting in the static fluorescence quenching of 7S. Compared with free Cur, the retention rates of Cur in 7S-Cur were approximately 1.12 and 1.70 times higher under UV exposure at 365 nm or heating at 75 °C for 120 min, respectively, as well as 7S-Cur showing approximately 1.50 times higher antioxidant activity. During simulated gastrointestinal experiments, 7S-Cur exhibited a better sustained-release property than free Cur. CONCLUSION: The self-assembled 7S nanocarriers prepared using a pH-shifting method effectively improved the antioxidant activity, environmental stability and sustained-release property of Cur. Therefore, 7S isolated from pea protein could be used as potential nanocarriers for Cur. © 2023 Society of Chemical Industry.

Gesture Recognition System Using Reduced Graphene Oxide-Enhanced Hydrogel Strain Sensors for Rehabilitation Training.

Gesture recognition systems epitomize a modern and intelligent approach to rehabilitative training, finding utility in assisted driving, sign language comprehension, and machine control. However, wearable devices that can monitor and motivate physically rehabilitated people in real time remain little studied. Here, we present an innovative gesture recognition system that integrates hydrogel strain sensors with machine learning to facilitate finger rehabilitation training. PSTG (PAM/SA/TG) hydrogels are constructed by thermal polymerization of acrylamide (AM), sodium alginate (SA), and tannic acid-reduced graphene oxide (TA-rGO, TG), with AM polymerizing into polyacrylamide (PAM). The surface of TG has abundant functional groups that can establish multiple hydrogen bonds with PAM and SA chains to endow the hydrogel with high stretchability and mechanical stability. Our strain sensor boasts impressive sensitivity (Gauge factor = 6.13), a fast response time (40.5 ms), and high linearity (R2 = 0.999), making it an effective tool for monitoring human joint movements and pronunciation. Leveraging machine learning techniques, our gesture recognition system accurately discerns nine distinct types of gestures with a recognition accuracy of 100%. Our research drives wearable advancements, elevating the landscape of patient rehabilitation and augmenting gesture recognition systems' healthcare applications.

Preparation of high complex concentration emulsion stabilized by soy protein/dextran sulfate composite particles.

BACKGROUND: Soy protein isolate (SPI) can be used as an emulsifier to stabilize emulsions, though SPI is unstable under low acidic conditions. Stable composite particles of SPI and dextran sulfate (DS) can be formed by the electrostatic interaction at the pH 3.5. Furthermore, the SPI/DS composite particles can be used to prepare a high complex concentration emulsion. The stabilization properties of the high complex concentration emulsion were investigated. RESULTS: Compared to uncompounded SPI, the particle size of SPI/DS composite particles was smaller at 1.52 µm, and the absolute value of the potential increased to 19.9 mV when the mass ratio of SPI to DS was 1:1 and the pH was 3.5. With the DS ratio increased, the solubility of the composite particles increased to 14.44 times of the untreated protein at pH 3.5, while the surface hydrophobicity decreased. Electrostatic interactions and hydrogen bonds were the main forces between SPI and DS, and DS was electrostatically adsorbed on the surface of SPI. The emulsion stability significantly enhanced with the increase of complex concentration (38.88 times higher than at 1% concentration), the emulsion average droplet size was the lowest (9.64 µm), and the absolute value of potential was the highest (46.67 mV) when the mass ratio of SPI to DS was 1:1 and the complex concentration of 8%. The stability of the emulsion against freezing was improved. CONCLUSION: The SPI/DS complex has high solubility and stability under low acidic conditions, and the emulsion of the SPI/DS complex has good stability. © 2023 Society of Chemical Industry.

Infrared radiation blanching-inhibited browning and extended shelf life of pecan kernels.

To evaluate infrared radiation (IR) blanching in comparison to conventional hot water (HW) blanching in inhibiting the browning and extending the shelf life of pecan kernels, the technology of IR blanching at 500-700 W for 90-45 s or HW blanching at 90°C for 60 s, and subsequently drying with hot air at 60, 70, and 80°C, respectively, was used, and then the activities of lipoxidase (LOX) and polyphenol oxidase (PPO), antioxidant capacities, color change, microscopic structure, and the shelf life of kernels were analyzed. Results showed that IR blanching not only significantly decreased the subsequent drying time but also effectively inactivated the activities of LOX and PPO, showing a lower residual activity of 15.74%-40.41% and 16.75%-56.25%, respectively. A higher retention of total phenolics was observed in kernels subjected to IR blanching, from 25.03 ± 0.04 to 29.50 ± 0.96 mg GAE/g compared with HW blanching (14.43 ± 0.07 mg GAE/g). Meanwhile, IR-blanched samples showed lower peroxide values, p-anisidine values, total color difference values, browning index, quinones contents, and lipofuscin-like pigments levels but had higher 2,2-diphenyl-1-picrylhydrazyl inhibition rate and better storage stabilities than HW-blanched samples. The technology of IR blanching at 600 W for 60 s followed by drying with hot air at 70°C for 40 min is suitable for producing pecan kernels with better qualities and a longer shelf life, through inactivating the endogenous enzymatic reactions and inhibiting the formation of lipofuscin-like pigments. PRACTICAL APPLICATION: Blanching is an essential pretreatment of food processing. Conventional blanching is achieved by hot water, which has some disadvantages of low-intensity enzyme inactivation, loss of water-soluble substances, etc. In this study, the potential of using infrared blanching, prior to drying, was studied to find solutions to improve the nutritional value, and the shelf life of pecan kernels. The results showed that infrared blanching at 600 W for 60 s followed by drying with hot air at 70°C for 40 min could inhibit the color degradation, improve the oxidation resistance, and prolong the shelf life of kernels.

Effect of sodium trimetaphosphate on the physicochemical properties of modified soy protein isolates and its lutein-loaded emulsion.

Due to people's pursuit of healthy and green life, soy protein isolate (SPI) is occupying a larger and larger market share. However, the low solubility of SPI affects its development in the field of food and medicine. This paper aimed to investigate the effects of sodium trimetaphosphate (STMP) on the functional properties and structures of phosphorylated SPI and its lutein-loaded emulsion. After modification by STMP, the phosphorus content of phosphorylated SPI reached 1.2-3.61 mg/g. Infrared spectrum and X-ray photoelectron spectrum analysis confirmed that PO4 3- had phosphorylation with -OH in serine of SPI molecule. X-ray diffraction analysis showed that phosphorylation destroyed the crystal structure of protein molecules. Zeta potential value of phosphorylated SPI decreased significantly. When STMP addition was 100 g/kg, particle size of protein solution decreased to 203 nm, and solubility increased to 73.5%. Furthermore, emulsifying activity and emulsifying stability increased by 0.51 times and 8 times, respectively. At the same protein concentration (1%-3% [w/w]), lutein-loaded emulsion prepared by phosphorylated SPI had higher absolute potential and smaller particle size. The phosphorylated protein emulsion at 2% concentration had the best emulsion stability after storage for 17 days. PRACTICAL APPLICATION: Phosphorylation significantly improved the emulsifying properties and solubility of SPI. Phosphorylated SPI significantly improved the stability of lutein-loaded emulsion. It provides theoretical basis for the application of phosphorylated SPI as emulsifier in delivery system and broadens the development of lutein in food and medicine field.

The preparation of soy glycinin/sugar beet pectin complex network gels catalyzed by laccase under weakly acidic conditions.

BACKGROUND: Traditional soy protein gel products such as tofu, formed from calcium sulfate or magnesium chloride, have poor textural properties and water retention capacity. Soy glycinin (SG) is the main component affecting the gelation of soy protein and can be cross-linked with polysaccharides, such as sugar beet pectin (SBP), and can be modified by changing system factors (e.g., pH) to improve the gel's properties. Soy glycinin/sugar beet pectin (SG/SBP) complex double network gels were prepared under weakly acidic conditions using laccase cross-linking and heat treatment. The structural changes in SG and the properties of complex gels were investigated. RESULTS: Soy glycinin exposed more hydrophobic groups and free sulfhydryl groups at pH 5.0. Under the action of laccase cross-linking, SBP could promote the unfolding of SG tertiary structures. The SG/SBP complex gels contained 46.77% ß-fold content and had good gelling properties in terms of hardness 290.86 g, adhesiveness 26.87, and springiness 96.70 mm at pH 5.0. The T22 relaxation time had the highest peak, and magnetic resonance imaging (MRI) showed that the gel had even water distribution. Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) indicated that the SG/SBP complex network structure was uniform, and the pore walls were thicker and contained filamentous structures. CONCLUSION: Soy glycinin/ sugar beet pectin complex network gels have good water-holding, rheological, and textural properties at pH 5.0. The properties of soy protein gels can be improved by binding to polysaccharides, with laccase cross-linked, and adjusting the pH of the solution. © 2022 Society of Chemical Industry.

Encapsulation of curcumin in soluble soybean polysaccharide-coated gliadin nanoparticles: interaction, stability, antioxidant capacity, and bioaccessibility.

BACKGROUND: Gliadin nanoparticles are used as a delivery system for active substances because of their amphiphilicity and bioavailability. However, they are susceptible to destabilization by external agents. In this study, gliadin nanoparticles stabilized by soluble soybean polysaccharide (SSPS) were prepared by antisolvent precipitation. Formed stable complex nanoparticles were applied to protect and deliver curcumin (Cur). RESULTS: Gliadin/SSPS nanoparticles with the smallest particle size (196.66 nm, polydispersity index < 0.2) were fabricated when the mass ratio of gliadin to SSPS was 1:1 at pH 5.0. SSPS-stabilized gliadin nanoparticles had excellent stability at pH 3.0-8.0, 0.02-0.1 mol L-1 NaCl and at 90 °C heat. Gliadin/SSPS nanoparticles were used to encapsulate the Cur. The encapsulation efficiency of the Cur-loaded gliadin/SSPS nanoparticles was 84.59%. Fourier transform infrared spectroscopy and fluorescence spectrophotometry showed that the main forces were hydrogen bonds, electrostatic interactions and hydrophobic interactions between gliadin and SSPS. The X-ray diffraction patterns exhibited that the crystalline form of Cur converted to an amorphous substance. The retention rates of Cur-loaded gliadin/SSPS nanoparticles reached 79.03%, 73.43% and 87.92% after ultraviolet irradiation for 4 h, heating at 90 °C and storage at 25 °C for 15 days, respectively. Additionally, simulated digestion demonstrated that the bioavailability of gliadin/SSPS-Cur nanoparticles was four times higher than that of free Cur. CONCLUSION: This study showed that SSPS improved the stability of gliadin nanoparticles. Gliadin/SSPS nanoparticles have the function of loading and delivering Cur. © 2022 Society of Chemical Industry.

Properties of transglutaminase-induced myofibrillar/wheat gluten gels.

Gelation properties of myofibrillar protein (MP)/wheat gluten (WG) induced by glutamine transaminase (TGase) were studied. Results showed that the inclusion of transglutaminase increased the gel strength, water-holding capacity (WHC), and nonfreezable water (Wnf) of MP/WG mixture. Circular dichroism (CD) analysis showed that the ß-sheet and random coil content of the MP/WG treated with TGase addition increased by 12.1% and 3.7%, while the α-helix and ß-turn content decreased by 14.2% and 1.8%. Rheological measurements showed that TGase induced higher energy storage modulus value during the MP/WG gel heating-cooling cycle. the hydrogen bond and hydrophobic interaction content of the MP/WG gels increased by 80 and 120 ug/L, and the disulfide bond decreased by 200 ug/L, with TGase addition was increased from 0 to 120 U/g protein. Scanning electron microscope (SEM) showed that MP/WG gel with TGase had uniform and dense network structure. PRACTICAL APPLICATION: The properties of myofibrillar/wheat gluten gel induced by TGase crosslinking was studied. The gel structure and water holding capacity of MP/WG were improved by the cross-linking of TGase. The study of the gel properties of MP/WG induced by TGase crosslinking also can provide a theoretical basis for analyzing the effect of TGase on the application of gluten protein in complex meat emulsion system.

Study on preparation of acylated soy protein and stability of emulsion.

BACKGROUND: Protein can be used as an emulsifier to improve emulsion stability at the interface of water-in-oil emulsion. However, natural soybean protein isolate (SPI) does not meet the high demands as an emulsifier in the food industry. The effect of acylation modification by ethylenediaminetetraacetic dianhydride (EDTAD; 0-300 g kg-1 ) on the physicochemical properties of SPI was studied. RESULTS: The results of the Fourier transform infrared spectra analyses showed that carboxyl groups were introduced into the SPI structure by the EDTAD treatment. The carboxyl concentration of SPI was increased by 30-74.07% with an increase in EDTAD addition from 50 to 300 g kg-1 . When 150 g kg-1 EDTAD was added, the surface hydrophobicity, the emulsifying activity, and the absolute value of the zeta potential were increased by 213%, 120%, and 68% respectively, and the particle size decreased to 247 nm. The droplet size of emulsion decreased to 10 µm when pH was 6. At the same concentration of SPI and pH, the absolute value of zeta potential of the emulsion was biggest. A comparison of the emulsions during storage showed the improvement of emulsion stability was related to the increase in the zeta potential and the decrease in the average particle size. The experimental group showed no destabilization on day 21, and no obvious aggregation phenomenon was observed. CONCLUSION: Acylation modification by EDTAD changed the emulsifying properties of SPI and enhanced the stability of the SPI emulsion. © 2021 Society of Chemical Industry.

Gel properties of transglutaminase-induced soy protein isolate-polyphenol complex: influence of epigallocatechin-3-gallate.

BACKGROUND: Traditional soy protein isolate (SPI)-based gel products, such as tofu, are generally produced by heating and by addition of metal salt ions to adjust the hydrophobicity and electrostatic force of soybean protein to facilitate the formation of a uniform network structure. However, the gelation rate of the soy protein gel network structure is difficult to control. Theoretically, epigallocatechin-3-gallate (EGCG) could be used to alter the surface hydrophobicity of thermally induced SPI to improve its gelation rate and form a more uniform network structure, thus improving SPI-based gel properties (hardness, water holding capacity and rheological properties). RESULTS: An SPI-EGCG complex (SPIE) was prepared, and properties of the resulting gel, following induction of transglutaminase (TG), were evaluated. Results showed that EGCG is bound to thermally induced SPI primarily via hydrophobic and hydrogen bonding, thus altering the secondary structure composition and reducing surface hydrophobicity of proteins in thermally induced SPI. Furthermore, the optimum amount of EGCG required to improve the gel strength, water holding capacity and rheological properties was ≤0.04:1 (SPI 1 g L-1 ; EGCG:SPI, w/w). Thermal stability analysis further indicated that EGCG in SPIE was more stable than free EGCG after heating. CONCLUSION: This study demonstrated that EGCG can improve the gel properties of TG-crosslinked SPIE, while EGCG in SPIE exhibits enhanced thermal stability. Additionally, the results of this study provide a novel strategy for the development of SPI-based gel foods with improved gel properties and that are enriched with bioactive compounds. © 2020 Society of Chemical Industry.

Effect of Partial Hydrolysis with Papain on the Characteristics of Transglutaminase-Crosslinked Tofu Gel.

The effects of partial enzymatic hydrolysis of soymilk on the characteristics of transglutaminase (TG)-crosslinked tofu gel were studied. SDS-PAGE showed that the molecular weight of the partially hydrolyzed soybean protein was reduced to that of a digested peptide (less than 43.0 kDa) when papain was added at more than 50 µL/100 mL soymilk. The content of free sulfhydryls, ß-sheets, and random coils in papain-treated soymilk increased. When TG was added to soy milk after papain treatment and tofu gel was formed, its storage modulus increased from 957.44 to 1241.39 Pa. The gel strength, water-holding capacity, and nonfreezing water content of the tofu gel were greater than those without enzyme treatment. Scanning electron microscopy revealed that limited papain hydrolysis stimulated TG-catalyzed cross-linking of soymilk to form a dense gel network structure, whereas an extended enzymatic hydrolysis of soymilk did not promote crosslinking by TG. PRACTICAL APPLICATION: This work investigated the effect of partial hydrolysis on TG cross-linked tofu gel. Partial hydrolysis of soybean protein with papain can promote TG cross-linking reaction, thus form a dense network structure, increase gel strength, and water-holding capacity. Therefore, it can be used to produce a good gel product with higher gel strength, springiness, water-holding capacity, and a more dense microstructure.

Transglutaminase-set colloidal properties of wheat gluten with ultrasound pretreatments.

The low solubility of wheat gluten limits its accessibility. This work aimed to study the impact of ultrasonic pretreatments on the gelation of wheat gluten. The pretreatments included ultrasound combined with alkali, urea, Na2SO3, with or without the addition of transglutaminase (TGase). The gel strength of wheat gluten was 287g/cm2 after treatment with Na2SO3/ultrasound/TGase. The free sulfhydryl and disulfide bond content was significantly affected by ultrasound treatment. After treatments including TGase crosslinking, the molecular weight of wheat gluten complexes became larger. The network formed by the wheat gluten was transformed into a dense and homogenous structure after the pretreatment with Na2SO3/ultrasound/TGase. The content of random coil of wheat gluten increased. The gelation of wheat gluten could also be significantly enhanced by Na2SO3/ultrasound treatment followed by TGase treatment. Using physical and chemical pretreatments to allow TGase to enhance the gelation of wheat gluten may increase its uses as a food additive.

Changes in chemical interactions and protein conformation during heat-induced wheat gluten gel formation.

In order to elucidate the heat-induced wheat gluten gel formation mechanism, changes in chemical interactions and protein conformation were investigated during gelation. The contribution of ionic and hydrogen bonds were found to decrease from 0.746 and 4.133g/L to 0.397 and 2.733g/L, respectively, as the temperature increased from 25 to 90°C. Moreover, the free SH content remarkably decreased from 37.91 to 19.79µmol/g during gelation. Ultraviolet absorption spectra and intrinsic fluorescence spectra suggested that wheat gluten unfolded during the heating process. In addition, wheat gluten gels treated at 80 and 90°C exhibited a "steric hindrance" effect, which can be attributed to the formation of aggregates. Fourier transform infrared spectra suggested that the random coil content increased at low temperatures (40 and 50°C), whereas the content of intermolecular ß-sheets due to protein aggregation increased from 38.10% to 44.28% when the gelation temperature was 90°C.

Transglutaminase-induced gelation properties of soy protein isolate and wheat gluten mixtures with high intensity ultrasonic pretreatment.

Soy protein isolate (SPI) and wheat gluten (WG) are widely used in commercial food applications in Asia for their nutritional value and functional properties. However, individually each exhibits poor gelation. In this study, we examined the microbial transglutaminase (MTGase)-induced gelation properties of SPI and WG mixtures with high intensity ultrasonic pretreatment. Ultrasonic treatment reduced the particle size of SPI/WG molecules, which led to improvements in surface hydrophobicity (Ho) and free sulfhydryl (SH) group content. However, MTGase crosslinking facilitated the formation of disulfide bonds, markedly decreasing the content of free SH groups. Ultrasonic treatment improved the gel strength, water holding capacity, and storage modulus and resulted in denser and more homogeneous networks of MTGase-induced SPI/WG gels. In addition, ultrasonic treatment changed the secondary structure of the gel samples as determined by Fourier transform infrared spectroscopic analysis, with a reduction in α-helices and ß-turns and an increase in ß-sheets and random coils. Thus, ultrasound is useful in facilitating the gelation properties of MTGase-induced SPI/WG gels and might expand their utilization in the food protein gelation industry.

Effect of Modified Wheat Gluten on Boiling Resistance Capacity of Pork Meatballs.

The effect of the modified wheat gluten (MWG) extender, prepared by alcalase-based hydrolysis and transglutaminase cross-linking, on meatballs was analyzed in this study. Here, we studied the effect of MWG addition on the boiling resistance capacity of pork meatballs (MB-MWG) at high temperature (100 °C) and increasing cooking time; meatballs with added soy protein isolates (MB-SPI) and raw wheat gluten (MB-WG) were used as references. The cooking loss, water-holding capacity (WHC), and textural properties of meatballs were investigated. The results revealed that MB-MWG showed lower cooking loss, which decreased by 49.16% compared to meatballs without added extenders when treated for 30 min. The WHC of MB-MWG significantly increased from 80.68% to 95.42%. The hardness, springiness, and chewiness (textural properties) of MB-MWG were also significantly increased by 97.05%, 6.68%, and 121.96%, respectively. The addition of MWG increased the cross-linking in meatballs during the cooking process, as indicated by the higher G'. SDS-PAGE indicated an obvious decrease in myosin heavy chain in MB-MWG cooked for 30 min at 100 °C, which was attributed to the interaction of myofibrillar proteins in pork meat with MWG. The nuclear magnetic resonance T2 relaxation time patterns indicated that MWG addition caused an increase in the bound water content, and decrease in the free water content, of meatballs. An analysis of the microstructures revealed that the MB-MWG formed the most regular and compact network. Therefore, MWG could be used as an ingredient to facilitate the processing of meat products.

Effects of microwave pretreatment and transglutaminase crosslinking on the gelation properties of soybean protein isolate and wheat gluten mixtures.

BACKGROUND: The integration of soybean protein isolate (SPI) with wheat gluten (WG) crosslinked via microbial transglutaminase (MTGase) may enhance the formation of ϵ-(γ-glutamyl)lysine covalent bonds, because SPI is rich in lysine and WG contains more glutamine. Microwave pretreatment may accelerate enzymatic reactions. In this study, we aimed to elucidate the effects of microwave pretreatment on the gelation properties of SPI and WG crosslinked with MTGase. RESULTS: Interestingly, the gel strength, water-holding capacity (WHC) and storage modulus (G') values of MTGase-induced SPI/WG gels were dramatically improved with increasing microwave power. Moreover, the MTGase crosslinking reaction promoted the formation of disulfide bonds, markedly reducing the free SH group and soluble protein content of gels. Fourier transform infrared spectroscopic analysis of SPI/WG gels showed that microwave pretreatment increased the proportion of α-helices and ß-turns and decreased the proportion of ß-sheets. Results from scanning electron microscopy indicated that the MTGase-induced SPI/WG gels had denser and more homogeneous microstructures after microwave pretreatment. CONCLUSION: The effect of microwave pretreatment is useful in advancing gelation characters of MTGase-induced SPI/WG gels and provides the possibility for expanding the application of food protein. © 2015 Society of Chemical Industry.

Effects of partial hydrolysis and subsequent cross-linking on wheat gluten physicochemical properties and structure.

The rheological behavior and thermal properties of wheat gluten following partial hydrolysis using Alcalase and subsequent microbial transglutaminase (MTGase) cross-linking were investigated. The wheat gluten storage modulus (G') and thermal denaturation temperature (Tg) were significantly increased from 2.26 kPa and 54.43°C to 7.76 kPa and 57.69°C, respectively, by the combined action of partial hydrolysis (DH 0.187%) and cross-linking. The free SH content, surface hydrophobicity, and secondary structure analysis suggested that an appropriate degree of Alcalase-based hydrolysis allowed the compact wheat gluten structure to unfold, increasing the ß-sheet content and surface hydrophobicity. This improved its molecular flexibility and exposed additional glutamine sites for MTGase cross-linking. SEM images showed that a compact 3D network formed, while SDS-PAGE profiles revealed that excessive hydrolysis resulted in high-molecular-weight subunits degrading to smaller peptides, unsuitable for cross-linking. It was also demonstrated that the combination of Alcalase-based partial hydrolysis with MTGase cross-linking might be an effective method for modifying wheat gluten rheological behavior and thermal properties.