Transglutaminase Concentration Research Articles

Multivariate image analysis for assessment of textural attributes in transglutaminase-reconstituted meat

The control of sensorial textural attributes has high interest to the meat industry focused on the recovery of the value of meat by-products by developing reconstituted meat pieces with added sensory and nutritional values. Sensorial analysis of foods is still a quite subjective methodology, highly dependent of a well-trained team of inspectors, which is simulated by textural analysis in order to measure objective physical properties. This work presents a non-destructive and contactless experimental methodology to predict the physical properties of a reconstituted meat product, based on integrating multispectral imaging and multivariate image analysis (MIA). The experiment was based on reconstituting grounded meat with different concentrations of transglutaminase (0.1, 1, 3, 6 and 10 %), from which textural properties and multispectral imaging data were measured. Multispectral images (UV, VIS and NIR wavelengths) were processed with chemometric procedures to obtain the distribution maps and score images, from which different blocks of features were extracted to generate feature vectors (basic statistics and co-occurrence matrix) for each image. The obtained regression models built with these features predicted all physical properties of the meat with Q2 > 0.90, after feature selection using VIPs. These results evidenced the capacity of multispectral imaging, combined with chemometric procedures, to capture the variability of physical properties induced by transglutaminase in a derivate meat product. It could represent the base of a potential contactless application for a meat industrial inspection, where work environments have strong hygienic requirements.

Structural and physicochemical properties of plant-based meat analogues from transglutaminase-modified soybean protein

Plant-based meat analogues (PBMA) have been developed for decades. The resemblance in PBMA to meat, in terms of physical properties and sensory attributes, is important for consumers. This study aims to investigate the effects of transglutaminase (TG) concentration (1, 3, 5% (w/w)) on modified textured vegetable soybean protein (TVP). The changes in TVP protein molecular weight, microstructure, texture profile, sensory quality and nutritional value of PBMA were investigated. The first set of analyses examined the impact of TG concentration on TVP structure and the results showed that the TVP protein band from SDS-PAGE were changed to a larger band at 36-40 kDa as compared to the control indicating the formation of a cross-linked protein. The modified TVP was used as a raw ingredient for PBMA development. The appearance and microstructure of PBMA from the TG-modified TVP showed that the uncooked PBMA with TG-modified TVP were not different from those of the control. With regard to the texture profile of PBMA, an increase in TG concentration resulted in an increase in hardness. A sensory evaluation revealed that the PBMA with 1%TG provided the highest overall acceptance score. Hence, the PBMA with 1%TG was selected for a nutritional analysis comparing steak to meat. The carbohydrate and fat content of PBMA with 1%TG were higher than those of meat while the protein content of PBMA with 1%TG consisted of a maximum of 70% meat. This research could lead to alternative plant-based foods in the food industry.

Elucidating the gas cell stabilization mechanism of buckwheat-wheat steamed bread induced by transglutaminase: A focus on the foaming and air-water interfacial properties of dough liquor

This work investigated the improvement mechanism of transglutaminase (TG) on the buckwheat-wheat steamed bread qualities from the view of protein structural, foaming and air-water interfacial properties of dough liquor (DL). TG reduced the hardness, ameliorated the crumb structure and enhanced the specific volume of buckwheat-wheat steamed bread by up to 9.0%. The DL yield, protein and water recovery were notably increased as the TG concentration increased to 0.2 U/g, then decreased with the higher TG concentrations. The low TG concentrations (<0.2 U/g) increased the protein molecular weight, and decreased the protein hydrophobicity, free amino and sulfhydryl groups content of DL. The high TG concentrations (>0.2 U/g) tended to induce both protein intermolecular and intramolecular cross-linking, which reduced the average particle size from 9.6 to 4.3 μm as the TG concentration increased from 0.2 to 1.0 U/g. TG markedly improved the foaming capacity and foam stability, decreased the surface tension and strengthened the interfacial films by enhancing the viscoelasticity modulus of buckwheat-wheat DL interfacial protein films. The topography of the air-water interfacial layer revealed that the TG-induced protein cross-linking led to a more homogeneous and denser topographical structure. This work will provide fresh insight into the effects of TG-induced protein cross-linking on gas cell stabilization and relate them to the buckwheat-wheat steamed bread quality properties.

Process optimization and characteristics of enzymatically cross-linked and ultrafiltrated whey

Whey, a byproduct of cheese production, is valued for its high-quality proteins. Ultrafiltration concentrates these proteins but faces challenges such as membrane fouling. This study investigates the use of transglutaminase to improve ultrafiltration efficiency by reducing fouling and optimizing protein recovery. Whey was divided into samples of whey in natura (WIN) and whey partially demineralized (WPD). Both were treated with different concentrations of transglutaminase (0, 0.5, 1.5, and 2.5% relative to protein mass) and ultrafiltered using polyethersulfone membranes at 4 bar. Effectiveness was evaluated by permeate flux and protein concentration, as well as physicochemical and structural characterizations such as FTIR, TGA, and molecular weight analysis. Transglutaminase reduced membrane fouling, increasing permeate flux. The 2.5% enzyme concentration was most efficient for WIN, while 1.5% was ideal for WPD. Enzymatic treatment increased protein concentration and thermal stability of the concentrates. FTIR analysis indicated the formation of cross-links between proteins. Molecular weight analysis revealed larger and more stable protein aggregates, improving ultrafiltration performance. This study suggests that transglutaminase is promising for optimizing whey ultrafiltration, improving protein recovery and process efficiency, with potential large-scale application in the food industry.

Effect of transglutaminase on the structure, properties and oil absorption of wheat flour

The structure, properties, as well as the oil absorption characteristics of wheat flour (WF) treated with varying concentrations of transglutaminase (TG) (0 U/g ∼ 50 U/g) were characterized. The content of free amino groups in WF modified by TG (TG-WF) decreased and protein aggregated. The isopeptide bonds and disulfide bonds played important roles in protein crosslinking. The thermal stability, the peak viscosity after gelatinization and protein secondary structure stability of TG-WF were improved. In addition, the oil absorption and surface oil content of TG-WF after frying were reduced. TG enhanced the protein-protein interactions in WF, so that protein played barrier roles in the process of high-temperature frying, protecting the starch particles covered by them from the infiltration of oil, thus reducing the oil absorption of TG-WF during frying. Among them, the oil content of TG-WF-30 U/g after frying was the lowest, which decreased by 10.73 % compared with the control group.

Effect of transglutaminase and laccase on pea protein gel properties compared to that of soybean

Enzyme cross-linking is a pivotal method for enhancing the functionality of plant proteins, offering improvements in texture, stability, and nutritional value, which are essential for food applications. Pea protein is increasingly used as it is not identified as allergenic and has fewer other negative health concerns. However, the lower gelling capacity compared with soybean protein has limited its application in plant-based meat or protein-based products. Thus, this study focused on investigating the effects of transglutaminase (TG) and laccase (LAC) and their concentrations on pea protein isolate (PPI) gelation, towards comparison with that of soybean protein isolate (SPI). Results showed that TG and LAC both contribute to the formation of PPI gels while exhibiting different action ways. As the TG content increased, the particle size of PPI significantly increased from 97.27 ± 4.61 μm to 146.67 ± 9.87 μm at 0.8% TG concentration, whereas the particle size remained constant with increasing LAC content. Both TG and LAC significantly enhanced the PPI gel properties, with 0.4% TG addition resulting in gel strength comparable to SPI and 0.8% TG content increasing PPI gel strength by approximately 4.2 times compared to the control, surpassing SPI. Moreover, PPI with TG treated demonstrated superior effects compared to LAC-treated gels at the same concentration. Water retention of gels increased from 89.37 ± 1.97% to 94.90 ± 3.86% with TG concentration increasing, while it decreased with LAC increasing. SDS-PAGE results revealed that TG promoted the formation of larger aggregates in PPI, indicating that legumin and vicilin were the main target sites for TG, while LAC was inapparent on molecular weight. The viscosity of PPI increased from 36.91 ± 2.32 Pa·s to 70.57 ± 1.00 Pa·s with 0.8% TG, while 0.8% LAC increased viscosity to 61.79 ± 1.32 Pa·s. Hydrogen bonds and disulfide bonds play a crucial role in the gel formation process facilitated by TG and LAC. Besides, TG is also expected to contribute through the formation of isopeptide bonds. These findings validated the potential of TG and LAC in improving the quality of PPI gels and provided insights for the application and development of cross-linking enzymes in the protein processing industry.

Utilizing Sweet Corn “Milk” Residue to Develop Fiber-Rich Pasta: Effects of Replacement Ratio and Transglutaminase Treatment on Pasta Quality

The rising demand for fiber-rich food products has fuelled the exploration of innovative approaches to enhance their dietary fiber content. Although adding dietary fiber-rich materials into pasta formula can increase the dietary fiber content, this approach counters several technological problems as the cooking and textural properties of the resulting pastas are usually negatively affected. This study is aimed at utilizing sweet corn “milk” residue (SCMR), a food by-product, and transglutaminase to develop fiber-rich pasta. Durum wheat semolina was replaced by SCMR powder at the ratio of 0 (control), 5, 10, 15, and 20% to make SCMR-fortified pasta. The chemical compositions and cooking and textural properties of the fortified pasta were then quantified. As the replacement ratio increased, the dietary fiber content, total phenolic content (TPC), and antioxidant properties of pasta were considerably improved while the cooking and textural attributes were negatively impacted. At 20% SCMR fortification, the dietary fiber content and TPC of the pasta were increased by 3.2 and 1.2 times, respectively, while the cooking loss increased by 73% as compared to those of the control pasta. Meanwhile, the chewiness, cohesiveness, tensile strength, and elongation rate at break of the 20% SCMR-fortified pasta were reduced by 19%, 26%, 21%, and 65%, respectively, compared to those of the control pasta. To improve the cooking properties and the textural properties of the fortified pasta, transglutaminase was added to the pasta dough with 20% SCMR. The effect of transglutaminase was enzyme-dose dependent. The cooking and textural qualities of pasta were improved as enzyme concentration increased 0 to 0.75 U/g protein and declined as the enzyme concentration increased from 0.75 to 1.25 g/U protein. At the optimal concentration of transglutaminase (0.75 U/g protein), the cooking loss reduced by 16% while the chewiness, cohesiveness, tensile strength, and elongation rate increased by 18%, 11%, 31%, and 32% compared to those without transglutaminase. Novelty Impact Statement. This study focuses on developing the dietary fiber-enriched pasta using sweet corn “milk” residue and transglutaminase enzyme. The results showed that replacing 20% durum wheat semolina with SCMR powder significantly enhanced the dietary fiber and total phenolic content of the pasta but negatively affect the cooking and textural properties of the pasta. Adding transglutaminase at 0.75 U/g protein to the SCMR-semolina blended dough successfully restored the adverse effects of SCMR on the cooking and textural properties. This study showed that dietary fiber-enriched pasta with improved cooking and textural properties can be prepared using the combination of SCMR and transglutaminase.

Investigating the Effect of Processing and Material Parameters of Alginate Dialdehyde-Gelatin (ADA-GEL)-Based Hydrogels on Stiffness by XGB Machine Learning Model.

To address the limitations of alginate and gelatin as separate hydrogels, partially oxidized alginate, alginate dialdehyde (ADA), is usually combined with gelatin to prepare ADA-GEL hydrogels. These hydrogels offer tunable properties, controllable degradation, and suitable stiffness for 3D bioprinting and tissue engineering applications. Several processing variables affect the final properties of the hydrogel, including degree of oxidation, gelatin content and type of crosslinking agent. In addition, in 3D-printed structures, pore size and the possible addition of a filler to make a hydrogel composite also affect the final physical and biological properties. This study utilized datasets from 13 research papers, encompassing 33 unique combinations of ADA concentration, gelatin concentration, CaCl2 and microbial transglutaminase (mTG) concentrations (as crosslinkers), pore size, bioactive glass (BG) filler content, and one identified target property of the hydrogels, stiffness, utilizing the Extreme Boost (XGB) machine learning algorithm to create a predictive model for understanding the combined influence of these parameters on hydrogel stiffness. The stiffness of ADA-GEL hydrogels is notably affected by the ADA to GEL ratio, and higher gelatin content for different ADA gel concentrations weakens the scaffold, likely due to the presence of unbound gelatin. Pore size and the inclusion of a BG particulate filler also have a significant impact on stiffness; smaller pore sizes and higher BG content lead to increased stiffness. The optimization of ADA-GEL composition and the inclusion of BG fillers are key determinants to tailor the stiffness of these 3D printed hydrogels, as found by the analysis of the available data.

Modification and texturization of plant proteins for vegetarian shrimp applications using transglutaminase

In recent years, vegetarian meat has seen significant growth in the market. However, vegetarian shrimp remains suboptimal, primarily because it is made from konjac, lacking the authentic texture of shrimp. This study aimed to enhance the texture of vegetarian shrimp by using various commercial plant proteins (soy, pea, Cyanobacteria, and wheat protein) combined with different transglutaminase (TGase) concentrations (0.1% and 0.5%). These were tested under specific temperatures (25 °C and 50 °C) and incubation periods (20 and 60 min) to establish a correlation between protein profiles and food texture. For comparison, three types of frozen shrimp (grass shrimp, prawn, and lobster) were used as benchmarks. The protein profiles and scanning electron microscope images of these frozen shrimps showed minor differences. The plant proteins profiles and textures were notably influenced by the varied TGase concentrations, temperatures, and incubation times. Moreover, when TGase was added, both soy and pea proteins achieved a texture akin to that of frozen lobster. Incorporating 0.5% TGase into soy and pea proteins resulted in vegetarian shrimp that closely resembled lobster in both protein profile and texture. Additionally, experimental data suggested that using Cyanobacteria and wheat proteins could enhance the flavor and springiness of the food. Overall, this study may serve as a valuable reference for the preparation of vegetarian shrimp.

Effects of Transglutaminase Concentration and Drying Method on Encapsulation of Lactobacillus plantarum in Gelatin-Based Hydrogel.

Lactobacillus plantarum is a kind of probiotic that benefits the host by regulating the gut microbiota, but it is easily damaged when passing through the gastrointestinal tract, hindering its ability to reach the destination and reducing its utilization value. Encapsulation is a promising strategy for solving this problem. In this study, transglutaminase (TGase)-crosslinked gelatin (GE)/sodium hexametaphosphate (SHMP) hydrogels were used to encapsulate L. plantarum. The effects of TGase concentration and drying method on the physiochemical properties of the hydrogels were determined. The results showed that at a TGase concentration of 9 U/gGE, the hardness, chewiness, energy storage modulus, and apparent viscosity of the hydrogel encapsulation system were maximized. This concentration produced more high-energy isopeptide bonds, strengthening the interactions between molecules, forming a more stable three-dimensional network structure. The survival rate under the simulated gastrointestinal conditions and storage stability of L. plantarum were improved at this concentration. The thermal stability of the encapsulation system dried via microwave vacuum freeze drying (MFD) was slightly higher than that when dried via freeze drying (FD). The gel structure was more stable, and the activity of L. plantarum decreased more slowly during the storage period when dried using MFD. This research provides a theoretical basis for the development of encapsulation technology of probiotics.

Optimizing gluten-free pasta quality: The impacts of transglutaminase concentration and kneading time on cooking properties, nutritional value, and rheological characteristics

This study investigated the influence of transglutaminase (TG) concentration and kneading time on gluten-free pasta's quality, texture, and nutritional content. Pasta dough composed of red rice, white quinoa, and tapioca flour was examined under seven treatment conditions. Variations in TG concentration (1%db, 1.5%db, and 2%db) and kneading time (5, 10, and 15 min) were applied. The findings demonstrated that as TG concentration and kneading time increased, cooking properties improved, evidenced by reduced pasta mass loss and increased swelling index and final moisture content. Furthermore, higher TG concentration and extended kneading enhanced pasta firmness to 9.1N, cohesiveness to 0.512, and chewability to 4.7 J. The treatment of 1.5% TG concentration and 10 min of kneading significantly maximized phenolic compound content with an increase from 17.54 mgGAE/100g to 39mgGAE/100g suggesting superior nutritional value. Rheological analysis revealed a distinct transition from Newtonian to non-Newtonian behavior, with the dough's shear-thinning nature becoming more noticeable as TG concentration and kneading time increased. This study provides a crucial understanding of the impacts of TG concentration and kneading time on gluten-free pasta, offering an effective strategy for optimizing pasta production processes.

Underlying mechanisms and combined effects of transglutaminase and κ-carrageenan on the quality profiles and in vitro digestibility of frankfurters

As a typical emulsified meat product, frankfurters have been widely consumed all over the world mainly due to their unique flavor, desired oral sensation, and higher nutritional values. The present study aimed to investigate the combined effects of different concentrations (0, 0.1, 0.3, and 0.5%, w/w) of transglutaminase (TG) and κ-carrageenan (KC, 0.2%, w/w) on the quality profiles and in vitro digestibility of frankfurters. The results showed that the combination of TG and KC significantly reduced the cooking loss and significantly promoted the emulsion stability of frankfurters (P < 0.05). Meanwhile, compared with frankfurters containing TG or KC alone, the simultaneous incorporation of 0.3% TG and 0.2% KC had the best optimal promoting effect on the textural properties of frankfurters, as well as the formation of denser and finer meat protein gel matrix. Moreover, hydrogen bonds and disulfide bonds were the main molecular forces of the frankfurters in the presence of TG and KC. In addition, the combination of TG and KC resulted in lower in vitro protein digestibility of frankfurters than those with TG or KC alone (P < 0.05), which was mainly because TG-induced cross-linking promoted the formation of ordered conformation of meat protein and subsequently enhanced the physical entanglement between KC and meat protein. In short, our results provided some vital information for the simultaneous incorporation of TG and KC in the processing of emulsified meat products.

Elevated tissue transglutaminase levels in aqueous humor of congenital cataractous eyes with long axial length

ObjectiveTo investigate the distribution of axial length (AL) and posterior staphyloma (PS) in congenital cataract (CC) patients. The correlation between AL and the concentration of tissue transglutaminase (TGM2) in the aqueous humor (AH) of cataractous eyes was also evaluated. MethodsCross-sectional data were collected from 499 children with CC who underwent phacoemulsification, anterior vitrectomy, and IOL implantation. AL measured by IOLMaster or A-scan ultrasonography and the presence of PS examined by B-scan ultrasonography were recorded. TGM2 levels in AH of 15 CC patients with normal axial length (NAL) and 15 CC patients with PS or long axial length (LAL) were measured by enzyme-linked immunosorbent assay. ResultsThe presence of PS in congenital cataractous eyes was 11.02%, and the presence of PS + LAL in congenital cataractous eyes was 29.06%. The AH levels of TGM2 in the cataractous group with NAL were lower than those in the cataractous group with PS or LAL (P < 0.001). The concentration of TGM2 in AH were positively correlated with AL of the patients’ eyes (P = 0.001). Additionally, we found that TGM2 expressed in the cytoplasm of lens epithelial cells of cataractous eyes, and the expression level increased with the AL value. ConclusionsThis study begins to lay the groundwork for investigating the characteristics of PS and LAL in patients with CC. Furthermore, AL was positively correlated with AH levels of TGM2.

Transglutaminase crosslinked fish gelatins for emulsion stabilization: From conventional to Pickering emulsions

Gelatin-stabilized emulsions, including conventional and Pickering emulsions, are gaining popularity. In this study, fish gelatins (FG) were modified with transglutaminase (TG) to prepare gelatin molecules, microgels, and their mixtures. The transition of emulsions from conventional to Pickering was observed as gelatins evolved from molecules to microgels. FG (3%) was cross-linked with TG at 0–30 U/g. FG evolved from gelatin molecules into thermo-irreversible hydrogels as TG increased. Without TG or at a low level of TG (10 U/g), FG mainly existed as gelatin molecules that were liquid at 25 °C. At high levels of TG (20 or 30 U/g), FG crosslinked and developed thermo-irreversible chemical hydrogels that were solid. As the concentration of TG increased, the protein molecular weights, zeta potentials, and surface hydrophobicity were significantly increased. Microfluidization was employed to prepare gelatin microgels. Different states of gelatins were mixed with sunflower oil to prepare conventional emulsions, Pickering emulsions, and mixtures. With increased TG, the emulsion droplets became more homogeneous, and protein networks formed around the oil droplets. Emulsions stabilized with modified FG displayed improved physical stability than those stabilized with unmodified FG. At 10 °C, the emulsions stabilized by a mixture of FG molecules and microgels presented higher physical stability. At 25 °C, Pickering emulsions stabilized by microgels showed improved anti-coalescence. The results of this work could provide valuable references for applying gelatin-stabilized conventional or Pickering emulsions with tunable properties, hence increasing the formulation flexibility of gelatin-based food products.

The effect of the application of transglutaminase enzyme on spaguetti type dry pasta

Dry pasta is a very popular product, which has a large and growing market in Brazil. Alongside the increase in consumption, there has been a search for products classified as “clean label”, which are alternatives with fewer additives in their composition. It is known that for pasta preparation it is necessary to use strong flour. The use of enzymes for the total or partial replacement of additives in the food industry can be expanded, as there are still little explored applications. Therefore, this work aimed to evaluate the effect of the enzyme transglutaminase (TG) in the preparation of spaghetti type dry pasta. Different samples of pasta were prepared and evaluated at four points of their shelf life (after 1, 15, 30 and 45 days) regarding the ideal cooking time, the mass increase of the cooked pasta, loss of solids in the cooking water and instrumental texture (pasta firmness). Eight assays were performed: TC (CONTROL without TG), TG1, TG2, TG3, TG4, TG5, TG6 (with 50, 100, 150, 200, 300, 1000 ppm of TG, respectively), and TP (standard containing ascorbic acid). The results showed that the tests with the highest concentration of TG showed an increase in mass of the cooked pasta, lower solids loss and greater firmness of the pasta after cooking. On the other hand, TP and TC did not differ significantly, and showed lower mass gain and greater solids loss during cooking. The results indicate that the application of TG may be promising to improve the technological quality of spaghetti type dry pasta.

Physicochemical, structural and in vitro gastrointestinal tract release properties of ι-carrageenan/sodium caseinate synbiotic microgels produced by double-crosslinking with calcium ions and transglutaminase

The aim of this study was to develop ι-carrageenan (ιC)/sodium caseinate (NaCas) synbiotic microgels loading Lacticasebacillus paracasei produced by double-crosslinking with calcium ions and different concentrations (0, 5, 10, and 15 U/g protein) of transglutaminase (TGase). The synbiotic microgels were coated/filled with pectic oligosaccharide (POS). Field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) analyses indicated that L. paracasei was successfully microencapsulated in synbiotic microgels. In Fourier transform infrared (FT-IR) analysis, the new formation of covalent and ionic crosslinking was observed in double-crosslinked synbiotic microgels. The encapsulation efficiency of L. paracasei was significantly increased from 87.82 to 97.68 % by increasing the concentration of TGase from 0 to 15 U/g protein, respectively. After exposure to simulated gastric fluid for 2 h and simulated intestinal fluid for 4 h, the survival rate of L. paracasei was significantly increased as the concentration of TGase increased.

Characterization of enzymatic cross-linking soy protein isolate xerogels and its shape memory effect induced by ethylcellulose

In this study, the deformation behavior of soybean protein isolate (SPI) xerogels cross-linked with different transglutaminase (TGase) concentrations was investigated. The gel properties of TGase cross-linked SPI were analyzed by rheology and texture. Results showed that 0.4% TGase completely promoted the intermolecular cross-linking, SPI molecules had more binding sites and α-helix content and less irregular curl structure. The presence of 0.4% TGase enhanced the water binding ability and thermal stability of SPI xerogel, and its denaturation temperature was up to 181.50 °C. The corresponding texture characteristics showed that hardness and elasticity were significantly increased by 182.90% and 25.00%, respectively. Results showed that SPI containing 0.4% TGase had the best 3D (three-dimension) shape change after hydration. However, excessive TGase (1.0% w/v) led to excessive lysine covalent cross-linking, which increases the porosity of the gel surface, causing the disrupted gel network. The research provides insights and new ideas for food-processing technology called 4D (four-dimension) food.

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.

A Study on the Mechanisms of Nanoparticle-Stabilized High Internal Phase Emulsions Constructed by Cross-Linking Egg White Protein Isolate with Different Transglutaminase Concentrations.

There is an increasing interest in the development of high internal phase emulsions (HIPE) stabilized by food-grade nanoparticles due to their potential applications in the food industry. In this study, cross-linked egg white protein isolates (cEPIs) are prepared by adding 10 u/g, 20 u/g, and 40 u/g of transglutaminase (TG), and the impacts of interface properties of cEPIs and emulsifying of HIPEs are investigated. Relative to the native EPI, the cEPIs have more irregular and agglomerated morphology, and the turbidity and hydrophobicity are significantly increased. The particle size and zeta potential of cEPIs considerably varied with the addition of TG. In HIPE, the formation, physical properties, and microstructure are characterized by visual observations, the Turbiscan stability index, and CLSM. The results indicated that stable and gel-like HIPEs are formed by cEPIs at oil internal phase (φ) values of 0.75–0.90. Especially for the enzyme additions of 20 u/g, the cEPIs had the best storage stability and the lowest TSI value (2.50) and formed a gel network structure at φ values of 0.9 microscopically. Overall, this study can enrich the theoretical frame of interface properties by enzyme treatment. Besides, it would be of great importance for the research of HIPE stabilized by cEPIs appropriate to be applied in food formulations.

Effect of crosslinking by microbial transglutaminase of gelatin films on lysozyme kinetics of release in food simulants

The effect of enzymatic crosslinking by microbial transglutaminase on the physico-chemical properties of gelatin-based films incorporated with lysozyme were investigated. Increase in the crosslinking degree of gelatin with microbial transglutaminase concentration in film-forming suspensions was correlated with a decrease of films thickness. Moreover, the enhancement in crosslinking resulted in a decrease of the solubility in water, as well as of the extent of swelling degree, and of the water vapor permeability of films and in an increase of films tensile strength. The kinetics of release at 4 °C of lysozyme from control non-reticulated films and reticulated films to either sodium acetate buffer, or 2% (w/v) agar gels in direct contact were compared. Interestingly, the kinetics of release of lysozyme were always slower from crosslinked films than from control films. This difference was higher for lysozyme release to agar gels, which was dominated by Fickian diffusion. Enzymatic crosslinking by microbial transglutaminase of gelatin-based films incorporated with lysozyme can thus effectively control the release of this food preservative.