TGase Treatment Research Articles

Enhanced tofu quality through calcium sulfate and transglutaminase treatment: physicochemical properties and digestibility analysis

SummaryTofu, a traditional soy‐based food, is widely consumed globally and serves as a significant source of plant protein. The quality of tofu can vary greatly depending on the coagulation process and the type of coagulants used. This study investigated the impact of a compound coagulant, consisting of transglutaminase (TGase) and calcium sulfate (CaSO4), on tofu quality, specifically focusing on pH, yield, water holding capacity (WHC), cooking loss, protein content, and in vitro digestibility. Soymilk was pre‐crosslinked with TGase for different durations (0, 1, 2, and 3 h) before the addition of CaSO4. Results indicated that TGase pre‐treatment significantly improved tofu yield and WHC, with optimal outcomes at 3 and 2 h, respectively. Cooking loss decreased with TGase treatment but increased at the 3‐h mark, suggesting over‐crosslinking. Electrophoresis revealed substantial protein crosslinking with TGase treatment, while in vitro digestion showed enhanced protein digestibility and higher peptide content in TGase‐treated samples. These findings underscore the potential of TGase treatment to enhance tofu's structural integrity and digestibility, offering valuable insights for optimising plant‐based protein processing to improve nutritional quality.

Transglutaminase Crosslinked Milk Protein Concentrate and Micellar Casein Concentrate: Impact on the Functionality of Imitation Mozzarella Cheese Manufactured on a Small Scale Using a Rapid Visco Analyzer.

In dairy-based imitation mozzarella cheese (IMC) formulations, intact casein is critical and imparts IMC with a firm and elastic, stringy, melted texture. Rennet casein (RCN) is the desired ingredient to provide intact casein in IMC and is preferred over milk protein concentrate (MPC) and micellar casein concentrate (MCC). Transglutaminase (TGase), a crosslinking enzyme, alters the physical properties of MPC or MCC and may change IMC functionality. The objective of this study was to determine the effect of TGase-crosslinked MPC and MCC powders on the functionality of IMCs. The TGase treatment included TGase at 0.3 (L) and 3.0 (H) units/g of protein and a control (C) with no TGase addition. Each IMC formulation was balanced for constituents and was produced in a Rapid Visco Analyzer (RVA). The MCC or MPC powder with high TGase enzyme in IMC formulation did not form an emulsion. The IMC containing TGase-treated powders had a significantly (p ≤ 0.05) higher RVA-viscosity during manufacture and transition temperature (TT), and a significantly (p ≤ 0.05) lower Schreiber melt test area. The IMC made from MPC (with or without TGase) had lower TT values and Schreiber melt test area as compared with that made from MCC. The TGase-treated MPC and MCC, when used for IMC manufacture, were comparable to IMC manufactured with RCN in texture and some measured melted characteristics. In conclusion, TGase treatment alters the melt characteristics of MCC and MPC in IMC applications.

Fabrication of resveratrol-loaded soy peptide nanogels with transglutaminase and in vitro gastrointestinal delivery and cholesterol-lowering effect

To improve the intestinal delivery of resveratrol, soy protein peptides (SPP) and transglutaminase (TGase) were used to prepare nanogels (NGs). The results demonstrated that, compared with native soy protein isolate (SPI) NG, SPP-NG showed a lower encapsulation efficiency (EE, 70.26%), a higher release efficiency (RE, 95.83%), and a smaller particle size (194.43 nm). However, the addition of TGase increased the EE and particle size to 74.37% and 217.73 nm, respectively. The RE of SPP-TGNG was also maintained at as high as 93.28%. Interestingly, SPP-TGNG exhibited optimal bile acid–binding capacity and cholesterol-lowering digests. The differences in delivery effects and morphology were attributed to structural changes in NGs. The unfolding and exposure of hydrophobic residues and weakened hydrogen bonds by hydrolysis resulted in a disordered and loose network structure, but it was beneficial to the production of cholesterol-lowering peptides and amino acids after digestion. The presence of TGase strengthened the crosslinking network by increasing β-sheet contents, hydrogen bonds, hydrophobic interactions, and isopeptide bonds. The alteration in multilevel structure would further affect the digestive products. The exposure of more hydrophobic residues and isopeptide crosslinking may be the intrinsic reason for the production of more hypocholesterolemic peptides and amino acids. This study indicated that the combination of hydrolysis and TGase treatment enhanced the delivery efficiency and bioactive properties of peptide-based NGs to resveratrol and revealed the internal mechanism between the structural changes and delivery efficiency. This work offers a theoretical foundation and technical suggestions for the production of peptide-based cargo systems and hydrophobic active substances.

Effect of transglutaminase crosslinking combined with lactic fermentation on the potential allergenicity and conformational structure of soy protein.

Food allergies are a growing concern worldwide, with soy proteins being important allergens that are widely used in various food products. This study investigated the potential of transglutaminase (TGase) and lactic acid bacteria (LAB) treatments to modify the allergenicity and structural properties of soy protein isolate (SPI), aiming to develop safer soy-based food products. Treatment with TGase, LAB or their combination significantly reduced the antibody reactivity of β-conglycinin and the immunoglobulin E (IgE) binding capacity of soy protein, indicating a decrease in allergenicity. TGase treatment led to the formation of high-molecular-weight aggregates, suggesting protein crosslinking, while LAB treatment resulted in partial protein hydrolysis. These structural changes were confirmed by Fourier transform infrared spectroscopy, which showed a decrease in β-sheet content and an increase in random coil and β-turn contents. In addition, changes in intrinsic fluorescence and ultraviolet spectroscopy were also observed. The alterations in protein interaction and the reduction in free sulfhydryl groups highlighted the extensive structural modifications induced by these treatments. The synergistic application of TGase and LAB treatments effectively reduced the allergenicity of SPI through significant structural modifications. This approach not only diminished antibody reactivity of β-conglycinin and IgE binding capacity of soy protein but also altered the protein's primary, secondary and tertiary structures, suggesting a comprehensive alteration of SPI's allergenic potential. These findings provide a promising strategy for mitigating food allergy concerns and lay the foundation for future research on food-processing techniques aimed at allergen reduction. © 2024 Society of Chemical Industry.

Novel soft food gels using beta-lactoglobulin via enzymatic crosslinking as agar gel alternatives

Soft food gels are of high interest for food innovation that can cater to the specific needs of various populations. This study explores the innovative development of soft beta-lactoglobulin (β-LG) gels through a green process that combines heat treatment and transglutaminase (TGase)-catalyzed crosslinking at a moderate pH. The optimal procedure involves heating β-LG solutions, pH 7.5 at 80 °C for 30 min to facilitate protein unfolding and aggregation, followed by TGase catalysis at 50 U TGase/g β-LG. This process produced soft and moist β-LG gels at a low concentration of 5% (w/v). The softness of β-LG gels was characterized through rheological measurements, suggesting a low storage modulus and high frequency dependence. Morphological observations of β-LG gels using TEM showed a loosely arranged network. SDS-PAGE and FTIR analyses indicated the formation of covalent disulfide bonds and isopeptide bonds in β-LG gels through the heat and TGase treatments. The potential of the novel β-LG gels as traditional agar gel substitutes was comparatively analyzed on their textural properties. Both gels showed distinctive jelly-like characteristics, whereas β-LG gels exhibited superior softness and reduced brittleness, positioning them as viable protein-based alternatives to agar gels for various applications in both food and nonfood sectors.

Pengembangan roti berbahan pati jagung dengan modifikasi enzimatis & pemanas ohmik (Kajian: pengaruh variasi tegangan dan transglutaminase terhadap karakteristik produk) [Development of corn starch-based bread with enzymatic modification & ohmic heating: study effect of voltage and transglutaminase variations on product characteristics

The main challenges in producing gluten-free bread are closely related to its development, texture, and nutrition. This research consisted of 2 stages. Stage 1 was aimed to determine the effect of voltage variations (70 V, 80 V, 90 V, 100 V, 110 V, 120 V, and conventional baking as a control) on bread characteristics and process parameters. The experiment was arranged as non-factorial in a completely randomized design with 3 replications. The best results of the first stage were applied in stage 2, aimed to determine the effect of various concentrations of TGase (0, 0.5, 1, 1.5, 2, and 2.5%). The data were processed using analysis of variance, then further tested using Tukey's at the 5% level. The 120 V voltage gradient treatment was found to be the best treatment. It shows specific volume 3.17±0.17 cm3/g, baking loss 14.58±1.50%, brightness 50.97±3.27, hardness 3.76±0.11, cohesive 0.34±0.03, pore density 84±2.52. In addition, baking at a higher voltage level increased the temperature rate and electrical conductivity. The 120 V voltage treatment shows the time required to reach a maximum temperature of 97°C was 3 minutes 5 seconds, and an electrical conductivity value of 0.26-0.51 S/m. Based on the TGase treatment, it was found that when bread dough was applied with a higher TGase concentration, the specific volume, hardness, chewiness, resilience, cohesiveness and springiness, average pore size, and pore porosity of the bread increased.

Sonicated-assisted TGase treatment enhances the techno-functional properties and protein conformation of reduced-salt chicken meat batter

The influence of sonication duration (0, 30 and 60 min) and TGase addition (Transglutaminase, 0 and 8.69 g/kg) on the pH, emulsion stability, textural characteristics, and protein conformation of reduced-salt chicken meat batter was analyzed. Compared with the sample without TGase or sonication treatment, the pH, β-sheet and β-turn contents of the samples treated with TGase and/or sonication were increased from 5.92, 20.4% and 13.3% to 6.13, 28.6% and 17.1%, respectively, led to the L*-value, cooking yield, emulsion stability, hardness, springiness, adhesiveness and chewiness were substantially higher, which shortened the initial relaxation time and decreased the mobility of the water, especially the immobilized water was increased from 76.6% to 92.8%. In addition, the pH, cooking yield, texture properties, β-sheet and β-turn contents of reduced-salt chicken meat batter considerably increased with increasing sonication duration, especially the cooking yield and hardness were increased from 80.7% to 58.5 N to 90.8% and 76.3 N, respectively, whereas they were not notably different after adding TGase, indicating that TGase more strongly impacted these variables compared with ultrasonic treatment. In conclusion, sonication-assisted TGase treatment induced changes in the protein conformation of reduced-salt chicken meat batter, leading to increased emulsion stability and gel properties.

Effect of transglutaminase on taste characteristics of pea protein hydrolysates through altering the composition of amino acids and peptides

This study investigated the effects of transglutaminase (TGase) treatment on the taste profiles and peptide compositions of pea protein isolate hydrolysates (PPIH) produced by Flavourzyme and protease 11,039. TGase significantly increased umami intensity by 50% and dramatically decreased bitterness by 40% in PPIH. While protein recovery, degree of hydrolysis, and peptide nitrogen percentage remained unaffected, TGase altered the relative proportions of taste compounds. This was evident through increased levels of umami, hydrophilic, and sweet-bitter amino acids in non-free amino acids, indicating the formation of peptides with umami potential. UPLC-MS/MS analysis confirmed that TGase facilitated the generation of longer peptides with higher umami potential compared to the short peptides in untreated PPIH. Simultaneously, the reduction in bitter components and the generation of umami substances contributed to the decrease in bitterness. Receptor-peptide docking studies confirmed that the newly formed peptides had higher binding affinities. Overall, TGase modification led to a shift in the substance profiles of PPIH, resulting in the creation of peptides with enhanced umami characteristics. These findings demonstrate the potential of combining TGase treatment with enzymatic hydrolysis to modify taste properties and develop flavorful plant-based protein ingredients.

A comparative study on the physicochemical characteristics and protein digestibility of tofu induced by magnesium chloride or combined with transglutaminase

SummaryIn this study, tofu was prepared through the addition of transglutaminase (TGase) for pre‐crosslinking at varying durations (1, 2 and 3 h), followed by the addition of magnesium chloride (MgCl2) to soymilk. The physicochemical properties and protein digestibility were analysed. Results indicated that, with the prolongation of TGase pre‐crosslinking time, the zeta‐potential absolute value and the average particle size of soymilk increased gradually. In contrast, the pH value remained unchanged (P > 0.05), suggesting that the colloidal stability of soymilk improved with TGase treatment. Both the water‐holding capacity (WHC) and gel strength of tofu gels exhibited a first increasing and then decreasing trend with prolonged pre‐crosslinking time. Notably, the highest WHC and hardness values of tofu gels prepared by adding MgCl2 after pre‐crosslinking with TGase for 1 h were 96.5 ± 0.5% and 363.9 ± 28.3 g, respectively. Subsequently, in vitro simulated gastrointestinal digestion of tofu samples prepared under this condition was conducted to determine changes in soluble protein content, small peptide content and protein hydrolysis spectrum. Gastric and intestinal digestion phases were the primary stages of protein hydrolysis, and the bioavailability of proteins in TGase+MgCl2‐induced tofu was higher than in MgCl2‐coagulated tofu. Therefore, tofu prepared through TGase pre‐treatment was more conducive to soybean protein digestion and absorption.

Continuous enzyme crosslinking modifying colloidal particle characteristics and interface properties of rice bran protein to improve the foaming properties

The improvement of rice bran protein (RBP) foaming properties by continuous Transglutaminase (TGase) enzymatic cross-linking was studied and the related mechanism was analyzed. Under the conditions of enzyme addition of 0.5 kat/kg of protein and 3 h of enzyme crosslinking time, the foam capacity value and foam volume ratio of BPR were increased to 375% and 79.45% respectively and the liquid drainage rate of RBP samples foam system was decreased. Particle size distribution, zeta potential and surface hydrophobicity indicated that TGase treatment has changed the surface properties and aggregation state of RBP affecting the adsorption of TGase treated RBP on the interface. Meanwhile circular dichroism and intrinsic fluorescence suggested that TGase treatment made the tertiary structure of RBP aggregation more compact. The behavior of the air-water interface revealed that compared to native RBP, TGase cross-linked RBP exhibited a faster and more complex adsorption process, and a higher surface dilatational modulus. Enzyme cross-linked RBP particles mainly stabilized the interfacial membrane by Pickering mechanism, and TGase could catalyze cross-linking of RBP at the interface to enhance the elastic modulus of the interface. This study provides theoretical support for application of protein particles prepared by TGase enzymatic cross-linking in foamed foods.

Manufacture of loaf‐type processed cheese products using transglutaminase crosslinked micellar casein concentrate and milk protein concentrate

The aim of this research was to determine the effect of transglutaminase (TGase; 0, 0.3 and 3.0 units/g of protein) crosslinked micellar casein concentrate (MCC) and milk protein concentrate (MPC) on the functionality of process cheese product (PCP) loaf‐type formulation. The results showed that TGase significantly (P ≤ 0.05) increased viscosity after manufacture. Higher TGase levels also significantly (P ≤ 0.05) affected post‐manufacture melt characteristics such as melt viscosity and melt area measured using a rapid visco analyser and Schreiber melt test respectively. The study shows that the TGase treatment alters meltability of PCP.

Comparison of the Effects of pH-Shifting, Acetic Acid Modification, and TGase Treatment on the Physicochemical and Functional Properties of Wheat Gluten Protein

Comparison of the Effects of pH-Shifting, Acetic Acid Modification, and TGase Treatment on the Physicochemical and Functional Properties of Wheat Gluten Protein

Acid gelation functionality of casein micelles in concentrated state: Influence of calcium supplementation or chelation combined with enzymatic stabilization

The main structure-building component in gelled dairy products is the casein micelle (CM). It was previously shown that in concentrated state of CMs, the changes of their compositional and colloidal properties in response to the addition or chelation of calcium divers from the reactions at milk-like casein concentration. This study aimed to evaluate the relationship between these specifically induced properties of CMs and the acid gelation functionality of a micellar casein concentrate (MCC). A covalent stabilization of the structures of pre-modified and native CMs by treatment with transglutaminase (Tgase) prior to acidification with glucono-δ-lactone was additionally tested. During acidification, structure formation was monitored in a rheometer to gain insights on mechanistic changes in the course of structural changes during acidification compared to gelation of unmodified MCC. Gelation pH, gel firmness, and serum binding capacity were analyzed to characterize gel structures at a final pH of 4.6. The structure formation process was highly affected by prior changes in composition, integrity, and structural stabilization of CMs. Gelation pH and acid gel firmness were reduced by ionic strength. Thermal and Tgase treatment induced opposing effects, leading to compensation when combined with prior salt supplementation. A synergistic increasing effect on serum binding capacity was found for trisodium-citrate supplementation and subsequent Tgase treatment. New mechanistic insights on acid gel structure formation progression were gained. This study provides a better insight into the relationship between structural CM properties prior to acid gelation and the resulting acidification progress, as well as the final acid gel properties.

Effects of transglutaminase on the physicochemical properties of surimi and kamaboko prepared by thermal and low level-pressure treatments

We investigated the effects of the presence or absence of transglutaminase (TGase) on the quality of tilapia surimi and kamaboko prepared at different thermal temperatures and pressures. TGase promoted the formation of surimi gel and covalent cross-linking under thermal (30°C–60 °C) and high-pressure treatments (0.1–300 MPa). Under heat treatment, TGase promoted myosin heavy chain (MHC) aggregation to form a 3D protein network. The TGase reaction was optimized at 50 °C, with no significant dependence on pressure. While the white index (WI) of TGase-treated surimi monotonically increased with temperature, and the lowest WI showed at 100 MPa, the other conditions were higher than it, with a maximum WI at 300 MPa. In the presence of TGase, both thermal (50 °C) and high-pressure (200–300 MPa) treatments improved the rheological properties of surimi and kamaboko. However, the effects on G′, G″ and Tan δ values of kamaboko were insignificant, mainly since the processing at 90 °C broke the non-covalent bonds based on hydrogen bonds formed by high-pressure treatments. Moreover, TGase treatment promoted the water holding capacity (WHC) of surimi and kamaboko. Hence, this study showed that with thermal treatment (50°C–60 °C), pressurization (200–300 MPa) caused the protein solubility of surimi and kamaboko to increase, irrespective of the TGase treatment. Notably, the protein solubility of surimi exceeded that of kamaboko.

Functional properties of milk protein concentrate and micellar casein concentrate as affected by transglutaminase treatment

Milk protein concentrate (MPC) and micellar casein concentrate (MCC) are used in foods to increase protein content and improve functional properties. The use of cross-linking enzymes such as transglutaminase (TGase) has the potential to modify the physical properties of MPC or MCC and may improve their functional properties. The objective of this study was to determine the effect of TGase treatment of MPC and MCC retentates on the functionality of MPC and MCC. MCC and MPC retentates were produced and treated with TGase enzyme at three levels, namely 0.0 TGase addition (control), 0.3 units/g of protein, and 3.0 units/g of protein. Treated retentates were then spray dried and various functional properties, including water (WAC) and fat (FAC) absorption capacity, alcohol (AS) and heat (HS) stability, solubility, solubility index (SI), effect of calcium chelating salts, and glucono-δ-Lactone (in yogurt like formulation) were tested. MPC samples had significantly (P ≤ 0.05) higher AS, HS, solubility, higher yogurt viscosity, water holding capacity (WHC), and syneresis, and significantly (P ≤ 0.05) lower SI, WAC, and FAC as compared with respective MCC treatments. TGase treatment significantly increased the AS, HS, SI, and significantly (P ≤ 0.05) decreased solubility. In MCC yogurt samples, there was a significant (P ≤ 0.05) decrease in rapid visco analyzer viscosity, WHC, and syneresis as enzyme levels increased. The effect of calcium chelating salts was more pronounced at a higher TGase level. The study demonstrates that TGase treatment will significantly affect and modify the functionality of MCC and MPC.

Modification of whey−soybean mixed protein by sequential high-pressure homogenization and transglutaminase treatment

The main purpose of this paper was to investigate the effect of High-pressure homogenization (HPH) and sequential HPH−Transglutaminase (TGase) treatment on the structural, physicochemical, and functional characteristics of mixtures of whey protein isolate (WPI) and soy protein isolate (SPI). Compared with the untreated WPI-SPI mixture protein, the mean particle size of WPI-SPI pretreatment with HPH (H-WS) and TGase-induced H-WS were reduced by up to 62%. Circular dichroism spectroscopy, surface hydrophobicity, and intrinsic fluorescence spectroscopy showed that HPH and sequential HPH−TGase treatment on WS increased in α-helix from 9% to 13%, decreased in β-sheet from 36% to 32%. The emulsification and foaming properties of the mixed protein were increased from 59 to 79 m2/g, 120%–158% respectively.

Soybean protein isolate treated with transglutaminase (TGase) enhances the heat tolerance of selected lactic acid bacteria strains to spray drying

TGase treated soy protein isolate (SPI) was confirmed to improve the survival of Lb. bulgaricus CICC 6047 subjected to spray drying. The viability of this strain increased from 70.69 % to 86.01 % due to elevating thermal stability. The smoother bacterial cell surface was observed by TGase treated SPI. TGase treatment changed the secondary conformation of SPI, having α-helical structure increased. Chemical bonds (hydrogen bond, CN bond, NH bond) proved the enzyme-modified SPI to have enhanced resistance to heat. The addition of TGase treated SPI allowed other LAB strains to tolerate the spray drying better. Their survival percentage after spray drying was 83.44 % for Le. mesenteroides CICC 6055, 80.64 % for Lb. acidophilus NCFM, 87.79 % for B. animalis BI-03 and 87.02 % for Lb. plantarum CICC 6009, respectively. The good survival of the selected LAB strains from TGase treated SPI powders was observed during storage of 8 weeks at 4 °C.

Use of micellar casein concentrate and milk protein concentrate treated with transglutaminase in imitation cheese products—Unmelted texture

The amount of intact casein provided by dairy ingredients is a critical parameter in dairy-based imitation mozzarella cheese (IMC) formulation because it has a significant effect on unmelted textural parameters such as hardness. From a functionality perspective, rennet casein (RCN) is the preferred ingredient. Milk protein concentrate (MPC) and micellar casein concentrate (MCC) cannot provide the required functionality due to the higher steric stability of casein micelle. However, the use of transglutaminase (TGase) has the potential to modify the surface properties of MPC and MCC and may improve their functionality in IMC. The objective of this study was to determine the effect of TGase-treated MPC and MCC powders on the unmelted textural properties of IMC and compare them with IMC made using commercially available RCN. Additionally, we studied the degree of crosslinking by TGase in MPC and MCC retentates using capillary gel electrophoresis. Three lots of MCC and MPC retentate were produced from pasteurized skim milk via microfiltration and ultrafiltration, respectively, and randomly assigned to 1 of 3 treatments: no TGase (control); low TGase: 0.3 units/g of protein; and high TGase: 3.0 units/g of protein, followed by inactivation of enzyme (72°C for 10 min), and spray drying. Each MCC, MPC, and RCN was then used to formulate IMC that was standardized to 21% fat, 1% salt, 48% moisture, and 20% protein. The IMC were manufactured by blending, mixing, and heating ingredients (4.0 kg) in a twin-screw cooker. The capillary gel electrophoresis analysis showed extensive inter- and intramolecular crosslinking. The IMC formulation using the highest TGase level in MCC or MPC did not form an emulsion because of extensive crosslinking. In MPC with a high level of TGase, whey protein and casein crosslinking were observed. In contrast, crosslinking and hydrolysis of proteins were observed in MCC. The IMC made from MCC powder had significantly higher texture profile analysis hardness compared with the corresponding MPC powder. Further, many-to-one (multiple) comparisons using the Dunnett test showed no significant differences between IMC made using RCN and treatment powders in hardness. Our results demonstrated that TGase treatment causes crosslinking hydrolysis of MCC and MPC at higher TGase levels, and MPC and MCC have the potential to be used as ingredients in IMC applications.

Use of micellar casein concentrate and milk protein concentrate treated with transglutaminase in imitation cheese products—Melt and stretch properties

Melt and stretch properties in dairy-based imitation mozzarella cheese (IMC) are affected by the amount of intact casein provided by dairy ingredients in the formulation. Rennet casein (RCN) is the preferred ingredient to provide intact casein in a formulation. Ingredients produced using membrane technology, such as milk protein concentrate (MPC) and micellar casein concentrate (MCC), are unable to provide the required functionality. However, the use of transglutaminase (TGase) has potential to modify the physical properties of MPC or MCC and may improve their functionality in IMC. The objective of this study was to determine the effect of TGase-treated MPC and MCC retentates on melt and stretch properties when they are used in IMC and to compare them with IMC made using RCN. The MCC and MPC retentates were produced using 3 different lots of pasteurized skim milk and treated with 3 levels of TGase enzyme: no TGase (control), low TGase: 0.3 units/g of protein, and high TGase: 3.0 units/g of protein. Each of the MCC and MPC treatments was heated to 72°C for 10 min to inactivate TGase and then spray dried. Each MCC, MPC, and RCN powder was then used in an IMC formulation that was standardized to 48% moisture, 21% fat, 20% protein, and 1% salt. The IMC were manufactured in a twin-screw cooker by blending, mixing, and heating various ingredients (4.0 kg). Due to extensive crosslinking, the IMC formulation with the highest TGase level (MCC or MPC) did not form an emulsion. The IMC made from MCC treatments had significantly higher stretchability on pizza compared with their respective MPC treatments. The IMC made from TGase-treated MCC and MPC had significantly lower melt area and significantly higher transition temperature (TT) and stretchability compared with their respective controls. Comparison of IMC made using TGase-treated MCC and MPC to the RCN IMC indicated no difference in TT or texture profile analysis-stretchability; however, the Schreiber melt test area was significantly lower. Our results demonstrated that TGase treatment modifies the melt and stretch characteristics of MCC and MPC in IMC applications, and TGase-treated MPC and MCC can be used to replace RCN in IMC formulations.

Fabrication and Characterization of the Egg-White Protein Chitosan Double-Layer Emulsion.

Egg-white protein has an abundance of hydrophobic amino acids and could be a potential emulsifier after modification. Here, egg-white protein was modified via ultrasonic and transglutaminase treatments to destroy the globular structure. The egg-white protein gel particles (EWP-GPs) were prepared and then a novel highly stable EWP-chitosan double-layer emulsion was constructed. When ultrasonic treatment was applied at 240 W and TGase (20 U/g EWP) treatment, the EWP-GPs had a low particle size and good emulsification performance. The particle size of EWP-GPs was a minimum of 287 nm, and the polymer dispersity index (PDI) was 0.41. The three-phase contact angle (θo/w) of EWP-GPs was 79.6° (lower than 90°), performing with good wettability. Based on these results, the EWP-chitosan double-layer emulsion was prepared through the EWP-GPs being treated with 240 W ultrasound, TGase, and chitosan in this study. When the double-layer emulsion had 0.6% (v/v) chitosan, the zeta potential of the double-layer emulsion was −1.1 mV and the double-layer emulsion had a small particle size (56.87 µm). The creaming index of double-layer emulsion at 0.6% (v/v) chitosan was 16.3% and the droplets were dispersed uniformly. According to the rheological results, the storage modulus (G′) was larger than the loss modulus (G″) in the whole frequency, indicating the formation of an elastic gel network structure in the emulsion. It is hoped to develop a novel food-grade stabilizer and a stable double-layer emulsion, providing new environment-friendly processing in hen egg products and delivery systems.