Properties of transglutaminase-induced myofibrillar/wheat gluten gels

Effect of transglutaminase on gelation and functional proteins of mung bean protein isolate

This study aimed to improve mung bean protein's gelation qualities via microbial transglutaminase (mTGase) cross-linking. The mTGase treatment significantly improved gel hardness and storage modulus (G') at higher enzyme levels (2 IU/g), peaking hardness at 3 h. The scanning electron microscopy imaging demonstrated more cross-linked structures at 2 IU/g, evolving into a dense network by 3 h. The water-holding capacity for mTGase-treated samples (2 IU/g, 3 h, 55 °C) tripled to 3.77 ± 0.06 g/g versus control (1.24 ± 0.02 g/g), alongside a 15 % decrease in zeta potential (-30.84 ± 0.901 mV versus control's -26.63 ± 0.497 mV) and an increase in emulsifying activity index to 4.519 ± 0.004 m2/g from 3.79 ± 0.01 m2/g (control). The confocal images showed a more uniform lipid droplet distribution in mTGase-treated samples, suggesting enhanced emulsifying activity. Thus, mTGase treatment significantly improved gel strength and emulsifying properties, making it ideal for plant-based seafood products.

On the modification of plant proteins: Traditional methods and the Hofmeister effect

With increasing consumer health awareness and demand from some vegans, plant proteins have received a lot of attention. Plant proteins have many advantages over animal proteins. However, the application of plant proteins is limited by a number of factors and there is a need to improve their functional properties to enable a wider range of applications. This paper describes the advantages and disadvantages of traditional methods of modifying plant proteins and the appropriate timing for their use, and collates and describes a method with fewer applications in the food industry: the Hofmeister effect. It is extremely simple but efficient in some respects compared to traditional methods. The paper provides theoretical guidance for the further development of plant protein-based food products and a reference value basis for improving the functional properties of proteins to enhance their applications in the food industry, pharmaceuticals and other fields.

Effect of κ-carrageenan on the quality of crayfish surimi gels

The demand for crayfish surimi products has grown recently due to its high protein content. This study examined the effects of varying κ-carrageenan (CAR) and crayfish surimi (CSM) concentrations on the gelling properties of CAR-CSM composite gel and its intrinsic formation process. Our findings demonstrated that with the increasing concentration of carrageenan, the quality of CAR-CSM exhibited rising trend followed by subsequently fall. Based on the textural qualities, the highest quality CAR-CSM was achieved at 0.3% carrageenan addition. With the exception of chewiness, and the cooking loss of the gel system was 1.62%, whiteness was 82.35%, and the percentage of β-sheets increased to 57.18%. Further increase in CAR (0.4-0.5%) addition resulted in internal build-up of LCAR-CSM, conversion of intermolecular forces into disulfide bonds and gel breakage. This study exudes timely recommendations for extending the CAR application for the continuous development of crayfish surimi and its derivatives and its overall economic worth.

Gel Properties and Protein Structures of Minced Pork Prepared with κ-Carrageenan and Non-Meat Proteins

Problems with minced pork include water release and low gel strength. This study aimed to investigate the effect of treatments with κ-carrageenan (κ-CAR), egg white powder (EWP), wheat gluten (WG), soy isolate protein (SPI), and a combination of these treatments on the gel properties and protein structures of minced pork. The cooking loss and trapped water within minced pork increased when additives were incorporated; in particular, the SPI group reached 1.31 ± 0.01% and 91.42 ± 0.20%. The hardness and chewiness of minced pork reached their maximum values (38.91 ± 0.80 N, 14.73 ± 0.41 N) when the WG was added. The κ-CAR/WG-minced pork gel network structure was the densest and most stable, characterized by increased hydrophobic interactions, disulfide bonds in the mince gel, and enthalpy value. The α-helix content with κ-CAR/WG treatment decreased from 27% to 7.8%, transforming into other secondary structures. This suggests that the addition of κ-CAR/WG can be a more effective combination for improving the quality of minced pork.

Investigating the physicochemical properties and air-water interface adsorption behavior of transglutaminase-crosslinking rapeseed protein isolate

Improving the technical functionality to adapt to the application of complex food systems is an important challenge for the development of plant protein ingredients. Herein, the correlation between the physicochemical properties and interfacial adsorption behavior of rapeseed protein isolate (RPI) at the air-water interface after transglutaminase (TG) treatment was investigated. The results of cross-linking degree, Fourier transform infrared spectroscopy (FTIR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the TG enzyme was able to catalyse cross-linking between lysine and glutamine residues of RPI. The foaming capacity of RPI was enhanced from 120 % to 150 % after TG cross-linking 5 h, whereas the average size (210-219 nm) of the RPI determined by dynamic light scattering did not change significantly. Besides, the hydrophobicity tended to increase overall under the enzyme treatment, while the surface electrostatic potential decreased. The former indicates the unfolding of the protein and reduces the kinetic barriers to protein adsorption at the air-water interface, with a consequent increase in disulfide bonding and surface pressure. Furthermore, as the enzyme treatment time increased, a significant increase in protein content of foam by 33.86 %. These findings provide novel insight into the foaming mechanism of TG cross-linking RPI.

Effects of Transglutaminase on Myofibrillar Protein Composite Gels with Addition of Non-Meat Protein Emulsion

The emulsions prepared by three non-meat proteins, sodium caseinate (SC), soy protein isolate (SPI) and egg white protein (EPI), were individually added to the continuous phase of myofibrillar protein (MP) sol to form MP composite gels to simulate meat products. The research aimed to investigate the effects of Transglutaminase (TGase) on the physicochemical properties, microstructure and water phase distribution of non-meat protein emulsion MP composite gels. The results of this study revealed that TGase played a crucial role in forming a tight gel network structure in the composite gels. This enhanced their ability to retain water and improved their overall gel strength. Additionally, TGase increased the gel formation temperature of myofibrillar proteins. Electrophoresis analysis showed that when catalyzed by TGase, there was a lighter band compared to those not catalyzed by TGase. This indicated that the addition of TGase facilitated cross-linking interactions between meat proteins and non-meat proteins in the composite gels. Furthermore, microscopy observations demonstrated that composite gels treated with TGase exhibited a more uniform microstructure. This could be attributed to an acceleration in relaxation time T2. The uniform network structure restricted the movement of water molecules in the gel matrix, thereby improving its water-holding capacity. Overall, these findings highlight how incorporating non-meat proteins into myofibrillar systems can be effectively achieved through enzymatic treatment with TGase. Such modifications not only enhanced important functional properties but also contributed towards developing alternative meat products with improved texture and moisture retention abilities.

Significantly Improving the Thermostability and Catalytic Efficiency of Streptomyces mobaraenesis Transglutaminase through Combined Rational Design

Streptomyces mobaraenesis transglutaminase has been widely used in food processing. We here significantly improved the catalytic properties of S2P-S23V-Y24N-S199A-K294L (TGm1), a highly stabilized variant of the transglutaminase. First, a virtual proline scan was performed based on folding free energy changes to obtain TGm1 variants with enhanced thermostability. Second, the residues within 15 Å of Cys64 in the enzyme-substrate complex of TGm1 were subjected to virtual saturation mutagenesis to generate the variants with reduced binding free energy and increased activity. After combining the favorable mutations, we obtained the variant FRAPD-TGm1-E28T-A265P-A287P (FRAPD-TGm2), exhibiting 66.9 min of half-life at 60 °C (t_1/2(60 °C)), 67.8 °C of melting temperature (T_m), and 71.8 U/mg of specific activity, which are 2-fold, 2.6 °C, and 43.8% higher than those of FRAPD-TGm1, respectively. At last, to increase the surface negative net charge of FRAPD-TGm2, we introduced the mutations N96E-S144E-N163D-R183E-R208E-K325E, yielding FRAPD-TGm3. The latter's t_1/2(60 °C), T_m, and specific activity were 122.9 min, 68.6 °C, and 83.7 U/mg, which are 83.8%, 0.8 °C, and 16.6% higher than the former, respectively. FRAPD-TGm3 is thus a robust candidate for transglutaminase application.