Search Results (94)

The covalent cross-linking of caseins by the enzyme transglutaminase (Tgase) stabilizes the structure of casein micelles. In our study, the effects of a pretreatment of skim milk (SM) by Tgase on milk protein fractionation by microfiltration were tested. Tgase was found to induce amount-dependent modifications of all milk proteins in SM and a reduction in deposit resistance for laboratory dead-end filtrations of up to 20%. This improvement in process performance could partially be confirmed in pilot-scale cross-flow filtrations of Tgase-pretreated SM and micellar casein solutions (MCC). These comparative trials with untreated retentates under a variation of ΔpTM (0.5–2 bar) at 10 and 50° revealed distinct differences in deposit behavior and achieved the reduction in deposit resistance in a range of 0–20%. The possibility of pre-fouling with enzymatically pretreated MCC prior to SM filtration was also investigated. Under different pre-fouling conditions, practical modes of retentate change, and pre-foulant compositions, a switch to untreated SM consistently resulted in an immediate and major increase in deposit resistance by 50–150%. This was partially related to the change in the ionic environment and the protein fraction. Nevertheless, our results underline the potential of Tgase pretreatment and pre-fouling approaches to alter filtration performance for different applications. Full article

In this study, curdlan was investigated as a substitute for egg-white protein, and the effects of different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) on lipid oxidation and the physicochemical properties of a novel low-salt surimi gel containing transglutaminase (TGase) and lysine were evaluated. The results indicated that adding appropriate curdlan concentrations (0.2%–0.4%, especially 0.4%) significantly inhibited lipid oxidation in the surimi gel, achieving the highest L* and whiteness values. The fracture strength, WHC, hardness, and chewiness of the gel increased by 23.87%, 6.70%, 32.80%, and 13.49%, respectively, compared to the control gel containing egg-white protein (p < 0.05). At 0.4% curdlan, the gel also enhanced the crosslinking within the surimi, improved its resistance to shear stress, significantly increased the G’ value, and shortened the T₂₁, T₂₂, and T₂₃ relaxation times, inhibiting the conversion of immobilized to free water in the gel and promoting a denser three-dimensional network structure. However, excessive curdlan amounts (0.6%–1.0%) led to a notable deterioration in the gel performance, causing a more irregular microstructure, the formation of larger cluster-like aggregates, and a negative effect on color. In conclusion, the combination of 0.4% curdlan with TGase and Lys is effective for preparing low-salt surimi products. Full article

Soy isolate protein (SPI), as a high-quality plant protein source, is often processed into various soy products. In this study, the physicochemical properties of SPI treated with transglutaminase (TGase) were investigated in correlation with emulsification characteristics and rheological behavior. The polyacrylamide gel electrophoresis with sodium dodecyl sulfate (SDS-PAGE) and Fourier-transform infrared spectroscopy (FTIR) and endogenous fluorescence spectrum analysis results showed that TGase was able to promote the covalent binding of lysine and glutamine residues in SPI. The moderate pre-crosslinking treatment of TGase (5–7.5 U/g TGase pre-crosslinked for 2 h or 5 U/g TGase pre-crosslinked for 2–3 h) improved the emulsification and gel properties to varying degrees: the nanoparticle and emulsification performance increased by 24.35% and the storage modulus of the gel increased by 288%. Furthermore, the surface charge of SPI increased due to the crosslinking impact of TGase, indicating a considerable rise in the surface electrostatic potential. Simultaneously, the protein surface exhibited a substantial increase in hydrophobicity, while the level of free sulfhydryl groups reduced. These changes indicate that TGase enzymatic crosslinking could significantly improve the structural stability of nanoparticles by enhancing the generation efficiency of covalent bonds between protein molecules. Full article

To increase the added value of peanut meal (PM, protein content of 46.17%) and expand its application in food processing, cold-pressed PM was modified via transglutaminase (TGase)-coupled glycation to enhance its functional properties. The effects of the modification conditions (i.e., PM concentration, PM/glucose mass ratio, temperature, and time) on the functional properties of PM were investigated, and its structural properties were evaluated using water contact angle measurements, fluorescence spectroscopy, and Fourier-transform infrared spectroscopy. It was found that TGase-coupled glycation modification altered the secondary structure of PM and increased both the water contact angle and the surface hydrophobicity, thereby significantly affecting its functional properties. Additionally, superior emulsification, foaming, and oil-absorbing properties were achieved for the modified PM, which were named EPM, FPM, and OPM, respectively (specimens under different modification conditions). Notably, the emulsification activity of the EPM sample was enhanced by 69.8% (i.e., from 18.48 to 31.38 m²/g); the foaming capacity of the FPM specimen was increased by 84.00% (i.e., from 21.00 to 46.00%); and the oil-absorbing capacity of the OPM sample was enhanced by 359.57% (i.e., from 1.41 to 6.48 g/g protein). Full article

Saltwater crocodile (SC; Crocodylus porosus) bone, an underutilized by-product, can be converted into high-value bio-calcium (Biocal), serving as a potential source of calcium and minerals. This study aimed to produce SC bone Biocal as functional gel enhancer for fish bologna development and to increase calcium intake. The resulting bone powder was evaluated for physicochemical, microbiological, and molecular properties. Additionally, the textural, physicochemical, structural, and sensorial properties of the formulated fish bologna incorporating Biocal at varying levels (0–10% w/w) were also evaluated. Biocal, obtained as a fine white powder, had a 16.83% yield. Mineral analysis showed 26.25% calcium and 13.72% phosphorus, with no harmful metals or pathogens detected. X-ray diffraction confirmed hydroxyapatite with 69.92% crystallinity, while calcium bioavailability was measured at 22.30%. Amino acid analysis indicated high levels of glycine, proline, and hydroxyproline, essential for collagen support. The findings confirmed that SC bone Biocal is beneficial and safe for food fortification. Incorporating SC Biocal (2–10% w/w) significantly affected the fish bologna characteristics (p < 0.05). As the Biocal level increased, the gel strength, hardness, and shear force also increased. The addition of 6% (w/w) Biocal significantly improved the textural property, without a detrimental effect on the sensory attributes of the bologna gel (p < 0.05). SDS-PAGE analysis showed TGase-enhanced myosin heavy chain (MHC) cross-linking, particularly in combination with Biocal. Moreover, the enriched Biocal–bologna gel exhibited a finer and denser microstructure. Thus, SC Biocal, particularly at 6% (w/w), can serve as a functional gel enhancer in surimi-based products, without compromising organoleptic quality. Full article

Surimi gel, a type of hydrocolloidal food, is formed through the gelation of fish meat proteins. Myosin heavy chain (MHC), a key myofibrillar protein, plays a crucial role in the formation of the gel network via both transglutaminase (TGase)-catalyzed and non-enzymatic polymerization. Gel disintegration in surimi is primarily attributed to the proteolytic degradation of MHC. This study focused on golden threadfin bream Nemipterus virgatus, a species characterized by low TGase activity and high protease activity at elevated temperatures. We investigated the competition between non-enzymatic polymerization and proteolytic degradation of MHC and their effects on gel mechanical properties using a mathematical model. A mathematical model based on kinetic reactions accurately reflected the changes in MHC observed through SDS-PAGE analysis during N. virgatus gel disintegration. Our results indicate that not only unpolymerized but also polymerized MHC was significantly degraded, which substantially contributed to the reduction in the mechanical properties of the N. virgatus surimi. Mathematically understanding the dynamics of MHC in surimi during heating helps promote the utilization of noncommercial fish species for surimi processing by enabling better control over surimi gel properties. Full article

The addition of Chinese yam powder (CYP) to wheat flour (WF) can compromise the elasticity of noodles due to weakening of the gluten network. To address this, we investigated the effects of TGase, vital wheat gluten (VWG), and egg white powder + sodium alginate (EWP + SA) on the quality of wheat yam composite flour noodles (color, cooking, textural, thermal properties, and in vitro starch digestibility). Our findings demonstrated that VWG, TGase, and EWP + SA exert distinct yet complementary effects on the quality of composite flour noodles. Combining TGase and VWG yielded the densest microstructure and better textural properties, including hardness, adhesiveness, and springiness. TGase and EWP + SA addition significantly increased slow digestible starch (SDS) content (G6: 33.81%) while reducing starch digestibility. These findings demonstrate that synergetic combinations of improvers, particularly TGase with VWG or EWP + SA, improve both the processing characteristics and nutritional quality of yam-based products. Full article

This study investigated the effects of transglutaminase (TGase) content (0%, 0.5%, 1%, 1.5%) and heat treatment (25 °C, 70 °C, 80 °C, 90 °C) on the structure and gel properties of camel casein protein. The results indicate that a TGase concentration of 0.5% combined with a heat treatment of 90 °C in SDS-PAGE facilitates the aggregation and crosslinking of protein molecules to form polymers, with the degree of crosslinking increasing alongside the TGase concentration. In FTIR, the treatment with TGase and heat resulted in a shift of the absorption peak of the amide I band, indicating a transition of the secondary structure from a loose to an ordered configuration. Additionally, surface hydrophobicity and heat enthalpy values were significantly increased, while the thermal transition temperature of casein gradually decreased. Following TGase binding and heat treatment, casein protein molecules formed a network structure characterized by small pore sizes and close crosslinking. Rheological analysis revealed that 0.5% TGase treatment significantly lowered the gel formation point of casein, promoted gelation, and effectively enhanced the mechanical properties and water-holding capacity of the casein gels. These findings provide theoretical reference for the development of camel protein modification and gel products. Full article

The bay scallop (Argopecten irradians) adductor is an attractive raw material for the production of surimi-like products. The gelling properties of raw materials directly affect the quality of surimi-like products. To assess the potential of processing frozen bay scallop adductors into surimi-like products, the effects of short-term freezing treatment on the endogenous transglutaminase (TGase) activity, myofibrillar protein (MP) structure and gelling properties of bay scallop adductors were investigated during 14 days of frozen storage (−18 °C). The results showed that TGase activity in adductor muscles increased significantly during the first 7 days. After 7–14 days, the carbonyl and sulfhydryl contents of the MPs notably changed (increased then decreased). The β-turn content of the MPs increased, indicating stretching and flexibility. Surface hydrophobicity, fluorescence intensity and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated changes in the tertiary structure of the MPs. Compared with gels from fresh samples, gels from scallop adductors frozen for 1 day presented significantly better texture characteristics (breaking force, gel strength, hardness, springiness, cohesiveness, chewiness) and higher water-holding capacity (p < 0.05). However, these properties significantly decreased on the 7th and 14th days (p < 0.05). Microstructural analysis revealed a more compact gel network from 1-day-frozen adductor muscles. These changes in TGase activity and MP structure are key factors influencing the gelling properties of frozen bay scallop adductors. This study provides new insights for improving gel properties during the frozen storage of bay scallop adductors. Full article

Partially substituting other proteins in soy-protein-based products is an effective method to meet nutritional and application requirements. However, the emulsifying properties of soybean protein isolates (SPI) when partially substituted with zein hydrolysates (ZH) remain unknown. In the present work, protein blend (0 h-SPI/ZH) from SPI and ZH with a ratio of 3.5: 1 (w/w) was treated by transglutaminase (TGase) for 0, 0.5, 1.0, and 1.5 h, respectively. SDS-PAGE analysis results indicate protein polymers were generated in SPI/ZH conjugates. Emulsifying activity of the conjugates (1.5 h-SPI/ZH) was significantly increased from 23.69 to 28.13 m² g⁻¹ in comparison with SPI, and there was no statistically significant difference (p < 0.05) in emulsion stability. The apparent viscosity, surface hydrophobicity of the SPI/ZH conjugates were significantly increased. Emulsion droplet size and zeta potential stabilized by 1.5 h-SPI/ZH were also increased; the values were 64.73 to 80.79 r.nm and −21.8 to −29.9 mV, respectively. CLSM results indicate that 1.5 h-SPI/ZH conjugates stabilized the emulsion and had a thicker adsorption layer. Overall, high values of negative zeta potential and suitable molecular weight distribution of the SPI/ZH conjugates might be responsible for the improved emulsifying property. This study provides insights for the preparation of soy-protein-based products as a promising food emulsifier. Full article

The application of crayfish muscle in surimi products is a potential way to promote their processing and ensure that it is of a high value. In this study, a one-way completely randomized design was used to prepare mixed surimi gels with different proportions of crayfish muscle. The effect of transglutaminase (TGase) on the improvement in the structural properties, water-binding capacity, micromorphology and protein conformation of blended gels was explored using mass spectrometry, centrifugation, scanning electron microscopy, and Fourier transform infrared spectroscopy. The results of thus study were analyzed by one-way ANOVA showed that in the absence of TGase, crayfish muscle made the microstructure of the blended gel looser and rougher, with a reduction in the strength of the gel and a decrease in the water holding capacity. The addition of 0.6% TGase was able to ameliorate this negative effect by promoting the formation of key chemical bonds and changes in protein conformation, which ultimately led to the enhancement of the crayfish–surimi blended gel properties. Practically, this study provides a viable strategy for incorporating crayfish into surimi products, enabling the development of novel, high-quality seafood products with improved texture and moisture retention, thereby enhancing consumer appeal and reducing waste in crayfish processing. Full article

This study investigated the effects of calcium oxide (CaO) derived from eggshells on the gelation properties of surimi prepared from giant snakehead (Channa micropeltes). Surimi gels were enriched with CaO at concentrations of 0, 2, 4, 6, 8, and 10 µmol/100 g, and their physicochemical, rheological, and structural characteristics were evaluated. The optimal CaO concentration (6 µmol/100 g) significantly enhanced gel strength by 48.2%, breaking force by 26%, and deformation by 18% compared to the control (p < 0.05). Expressible moisture content decreased from 16.88% to 7.12%, while total sulfhydryl groups were reduced to 5.17 µmol/100 g. Rheological analysis revealed increased storage modulus (G′) and loss modulus (G″), indicating enhanced gel elasticity and viscosity during thermal processing. Scanning electron microscopy (SEM) demonstrated the formation of a compact, uniform gel network with fine pores at the optimal CaO concentration. SDS-PAGE analysis confirmed that CaO promoted transglutaminase (TGase) activity and TGase catalyzes the formation of cross-links between myosin heavy chain (MHC) and disulfide bonds. These results demonstrate the potential of eggshell-derived CaO as a sustainable, cost-effective additive to enhance surimi gel quality. Full article

Transglutaminase (TGase) is an enzyme that catalyzes acyl transfer reactions by creating covalent cross-links between protein molecules and has been used to improve the physical and functional properties of protein-based foods. The objectives of this study were the extraction, purification, and biochemical characterization of TGase from sardine (Sardina pilchardus) flesh in order to provide a suitable TGase enzyme for food industry applications. The results showed a specific activity, yield, and purification fold of 357.14 U/mg protein, 36.74%, and 183.15, respectively. The enzyme exhibited maximal activity at 40 °C and pH 8.0, with a molecular weight of around 57 kDa. The effect of time on TGase thermal stability at 40 °C showed a gradual decrease in its catalytic activity during the incubation time until the enzyme was completely inactivated at 60 min. Additionally, the sardine TGase was found to be calcium-dependent. However, Mg²⁺ and Ba²⁺ ions were found to be effective in its activation to some extent and a total inhibition was shown by Zn²⁺ and Sr²⁺ ions. The TGase activity was affected markedly by NaCl and EDTA, and lost, respectively, about 80.7% and 36.49% from its activity by increasing the concentration (1.5 M NaCl and 20 mM EDTA). Based on the surface hydrophobicity and solubility results, the cross-linking of natural actomyosin mediated by TGase increased to a greater extent. The results revealed that sardine TGase possessed attractive qualities, making it a potential alternative to other TGase sources for food industry applications. Full article

Food allergies are a global concern, with β-lactoglobulin (β-LG) in bovine milk being a major allergenic protein. This study investigated the effects of transglutaminase (TGase)-mediated crosslinking on the antibody recognition capacity (ARC) and structural properties of β-LG, with the aim of developing hypoallergenic dairy products. β-LG solutions were treated with TGase at varying concentrations (0, 5, 10, 15, and 20 U/g) and durations (0, 6, 18, 24, and 42 h), followed by analysis using electrophoresis, enzyme-linked immunosorbent assay (ELISA), and spectroscopy. The results demonstrated that treatment with TGase at 20 U/g significantly reduced the ARC and immunoglobulin E (IgE) binding capacity of β-LG to 90.0 ± 0.4% and 58.4 ± 1.0%, respectively, with the optimal ARC reduction observed after 6 h of treatment (86.7 ± 1.2%, p < 0.05). Although electrophoresis did not reveal significant crosslinking of β-LG, ultraviolet absorption, fluorescence intensity, and hydrophobicity all increased with prolonged crosslinking time, while sulfhydryl content fluctuated irregularly. These findings suggest that β-LG underwent varying degrees of structural modification, which led to the masking of antigenic epitopes during the early stages (0–24 h), followed by their re-exposure at the later stage (42 h). Overall, these results highlight the potential of TGase to reduce β-LG potential allergenicity, presenting a promising strategy for the development of hypoallergenic dairy products. Full article

The flavor substances produced by the division of baijiu yeast during the winemaking process often determine the quality of white wine, and the difficulty of storing and transporting high-quality baijiu yeast is a bottleneck that restricts the development of China’s baijiu industry. It is widely accepted that drying microorganisms such as baijiu yeast is the best way to improve its storage and transport performance. Spray drying, as one of the most widely used microbial drying processes, with a high efficiency and low cost, is the hot spot of current research in the field of microbial drying, but it has the inherent defect of a low drying survival rate. In order to address this inherent defect, the present study was carried out with a high-quality white wine yeast, Modified Sporidiobolus Johnsonii A (MSJA), as the target. Firstly, an orthogonal experiment, Steep Hill Climbing experiment, and response surface experiment were sequentially designed to optimize the type and amount of protective agent added in the spray-drying process of MSJA. Then, the effects of glutamyl transaminase (TGase) treatment on the drying process of MSJA were revealed with the help of advanced equipment, such as laser particle sizer, environmental scanning electron microscope (ESEM), and Fourier-transform infrared scanner (FTIR). The results showed that the addition of “TGase-treated soybean isolate protein (SPI) + lactic protein (LP)” as an in vitro bacterial protectant and “14.15% trehalose + 7.10% maltose + 14.04% sucrose” TGase treatment can promote the cross-linking of protective proteins, reduce the distance between MSJA bacteria and protective proteins, and increase the glass transition temperature to enhance the protective effect of protective proteins, so as to improve the survival rate of MSJA during spray drying. Full article