Effects of sequential enzymatic hydrolysis and transglutaminase crosslinking on functional, rheological, and structural properties of whey protein isolate

Impacts of transglutaminase on the processing and digestion characteristics of glutinous rice flour: Insight of the interactions between enzymic crossing-linked protein and starch

Glutinous rice is extensively consumed due to its nutritious content and wonderful flavor. However, glutinous rice flour has a high glycemic index, and the storage deterioration of sweet dumplingsissevere. Transglutaminase (TG) was used to cross-link glutinous rice protein and improve the characteristics of glutinous rice products. The findings demonstrated that TG significantly catalysed protein cross-linking to form a dense protein network, reduced the viscosity of glutinous rice paste and improved the thermal stability. The protein network may physically block the access of starch granules to digestive enzymes to lower the digestion rate of starch, and attenuate the damage of ice crystal molecules to the starch structure to improve the freezing stability of starch gels. The cracking rate and water loss of sweet dumplings prepared using glutinous rice flour with TG treated for 60 min reduced significantly. In conclusion, this study broadened the application of TG in starch products.

Whey filtration: a review of products, application, and pretreatment with transglutaminase enzyme

In the cheese industry, whey, which is rich in lactose and proteins, is underutilized, causing adverse environmental impacts. The fractionation of its components, typically carried out through filtration membranes, faces operational challenges such as membrane fouling, significant protein loss during the process, and extended operating times. These challenges require attention and specific methods for optimization and to increase efficiency. A promising strategy to enhance industry efficiency and sustainability is the use of enzymatic pre-treatment with the enzyme transglutaminase (TGase). This enzyme plays a crucial role in protein modification, catalyzing covalent cross-links between lysine and glutamine residues, increasing the molecular weight of proteins, facilitating their retention on membranes, and contributing to the improvement of the quality of the final products. The aim of this study is to review the application of the enzyme TGase as a pretreatment in whey protein filtration. The scope involves assessing the enzyme's impact on whey protein properties and its relationship with process performance. It also aims to identify both the optimization of operational parameters and the enhancement of product characteristics. This study demonstrates that the application of TGase leads to improved performance in protein concentration, lactose permeation, and permeate flux rate during the filtration process. It also has the capacity to enhance protein solubility, viscosity, thermal stability, and protein gelation in whey. In this context, it is relevant for enhancing the characteristics of whey, thereby contributing to the production of higher quality final products in the food industry. © 2023 Society of Chemical Industry.

Advances in protein-based microcapsules and their applications: A review

Due to their excellent emulsification, biocompatibility, and biological activity, proteins are widely used as microcapsule wall materials for encapsulating drugs, natural bioactive substances, essential oils, probiotics, etc. In this review, we summarize the protein-based microcapsules, discussing the types of proteins utilized in microcapsule wall materials, the preparation process, and the main factors that influence their properties. Additionally, we conclude with examples of the vital role of protein-based microcapsules in advancing the food industry from primary processing to deep processing and their potential applications in the biomedical, chemical, and textile industries. However, the low stability and controllability of protein wall materials lead to degraded performance and quality of microcapsules. Protein complexes with polysaccharides or modifications to proteins are often used to improve the thermal instability, pH sensitivity, encapsulation efficiency and antioxidant capacity of microcapsules. In addition, factors such as wall material composition, wall material ratio, the ratio of core to wall material, pH, and preparation method all play critical roles in the preparation and performance of microcapsules. The application area and scope of protein-based microcapsules can be further expanded by optimizing the preparation process and studying the microcapsule release mechanism and control strategy.

Construction of a soybean protein isolate/polysaccharide-based whole muscle meat analog: Physical properties and freeze-thawing stability study

A growing interest has arisen in recreating real meat by mimicking its texture characteristics and muscle fiber structure. Our previous work successfully created meat analog fiber based on soybean protein isolate (SPI) and sodium alginate (SA) with the wet-spinning method. In this work, we analyzed the microstructure, texture profile, and water retainability of the assembled plant-based whole muscle meat analog (PMA) made of SPI/SA-based meat analog fiber and systematically studied the effect of different combinations and contents of transglutaminase (TG), salt, and soybean oil on the rheological behavior of the formulated adhesive. The estimated optimal condition that has the most similar texture characteristic with real chicken breast meat is: for every 1:1 mass ratio of simulated plant meat fibers to the adhesive, add 0.1 % TG enzyme addition in the adhesive and 100 mM NaCl addition. The physical behavior of PMA during cryopreservation was investigated through freeze-thaw cycles and freezing times. The addition of a small amount of oil and salt can efficiently prevent the PMA through freezing conditions which is comparable with the addition of D-Trehalose (TD). Overall, this study not only created a plant-based whole muscle meat analog product that is similar in texture to real chicken breast meat but also provided a new direction for constructing fiber-rich structure protein-based muscle meat analogs and their further commercialization.

Proteolysis improves the foaming properties of rice protein fibrils: Structure, physicochemical properties changes, and application in angel food cake

Proteolysis prior to fibrillation can change the functional properties of protein fibrils. This study aimed to investigate the effects of proteolysis pretreatment by alkaline protease on formation, structure, and foaming properties of rice protein fibrils. Thioflavin T fluorescence and conversion assays showed that proteolysis reduced the fibril formation capacity of rice protein. After 12 h of heating, the percent conversion of rice protein and rice protein hydrolysates to fibrils reached 60.32 ± 1.07% and 30.43 ± 2.01%, respectively. Transmission electron microscopy images showed that fibrils derived from rice protein hydrolysates had a longer contour length than rice protein fibrils. The foaming capacity and stability of rice protein hydrolysate fibrils increased by 16.70% and 11.27%, respectively, compared with those of rice protein fibrils. The addition of rice protein hydrolysate fibrils improved the texture of cakes. These results suggested that rice protein hydrolysate fibrils could be a promising plant-based foaming agent.

Synergistic improvement of quinoa protein heat-induced gel properties treated by high-intensity ultrasound combined with transglutaminase

BACKGROUND

Quinoa protein is enriched with a wide range of amino acids, including all nine essential amino acids necessary for the human body, and in appropriate proportions. However, as the main ingredient of gluten-free food, it is difficult for quinoa to form a certain network structure for lack of gluten protein. The aim of this work was to enhance the gel properties of quinoa protein. Therefore, the texture characteristics of quinoa protein treated with different ultrasound intensities coupled with transglutaminase (TGase) were investigated.

RESULTS

The gel strength of quinoa protein gel increased markedly by 94.12% with 600 W ultrasonic treatment, and the water holding capacity increased from 56.6% to 68.33%. The gel solubility was reduced and free amino content increased the apparent viscosity and the consistency index. Changes in the free sulfhydryl group and hydrophobicity indicated that ultrasound stretched protein molecules and exposed active sites. The enhanced intrinsic fluorescence intensity at 600 W demonstrated that ultrasonic treatment affected the conformation of quinoa protein. New bands emerged in sodium dodecylsulfate-polyacrylamide gel electrophoresis indicating that high-molecular-weight polymers were generated through TGase-mediated isopeptide bonds. Furthermore, scanning electron microscopy showed that the gel network structure of TGase-catalyzed quinoa protein was more uniform and denser, thereby improving the gel quality of quinoa protein.

CONCLUSION

The results suggested that high-intensity ultrasound combined with TGase would be an effective way to develop higher-quality quinoa protein gel. © 2023 Society of Chemical Industry.

Synergistic effect of microfluidization and transglutaminase cross-linking on the structural and oil-water interface functional properties of whey protein concentrate for improving the thermal stability of nanoemulsions

Generally, whey protein concentrate (WPC) undergoes high-temperature denaturation and aggregation, which reduces its emulsifying properties and is not conducive to as an emulsifier to maintain the thermal stability of emulsions. In this study, dynamic high-pressure microfluidization technology (DHPM) combined with TGase (TG) cross-linking was applied to prepare DHPM-TG-WPC, and the thermal stabilization mechanism of nanoemulsions prepared with DHPM-TG-WPC was explored. Results showed DHPM treatment could promote the formation of TG-crosslinked WPC polymers. Compared to WPC, the free sulfhydryl and free amino group content of DHPM-TG-WPC was significantly decreased (P < 0.05), the surface hydrophobicity and interfacial tension of DHPM-TG-WPC were increased by 45.23 % and 62.34 %, respectively. And its emulsifying stability index and interface protein adsorption was significantly enhanced (P < 0.05). Furthermore, compared to WPC, DHPM-WPC and TG-WPC, DHPM-TG-WPC-stabilized nanoemulsions showed the best 15 days of storage stability after thermal sterilization. This study provides a theoretical basis for the application of modified-WPC emulsion.

Effect of multiple-frequency ultrasound-assisted transglutaminase dual modification on the structural, functional characteristics and application of Qingke protein

Qingke protein rich in restricted amino acids such as lysine, while the uncoordination of ratio of glutenin and gliadin in Qingke protein has a negative impact on its processing properties. In this study, the effect of multiple-frequency ultrasound combined with transglutaminase treatment on the functional and structural properties of Qingke protein and its application in noodle manufacture were investigated. The results showed that compared with the control, ultrasound-assisted transglutaminase dual modification significantly increased the water and oil holding capacity, apparent viscosity, foaming ability, and emulsifying activity index of Qingke protein, which exhibited a higher storage modulus G' (P < 0.05). Meanwhile, ultrasound combined with transglutaminase treatment enhanced the cross-linking degree of Qingke protein (P < 0.05), as shown by decreased free amino group and free sulfhydryl group contents, and increased disulfide bond content. Moreover, after the ultrasound-assisted transglutaminase dual modification treatment, the fluorescence intensity, the contents of α-helix and random coil in the secondary structure of Qingke protein significantly decreased, while the β-sheet content increased (P < 0.05) compared with control. SDS-PAGE results showed that the bands of Qingke protein treated by ultrasound combined with transglutaminase became unclear. Furthermore, the quality of Qingke noodles made with Qingke powder (140 g/kg dual modified Qingke protein mixed with 860 g/kg extracted Qingke starch) and wheat gluten 60-70 g/kg was similar to that of wheat noodles. In summary, multiple-frequency ultrasound combined with transglutaminase dual modification can significantly improve the physicochemical properties of Qingke protein and the modified Qingke proteins can be used as novel ingredients for Qingke noodles.

Plant Protein versus Dairy Proteins: A pH-Dependency Investigation on Their Structure and Functional Properties

Plant proteins are constantly gaining attention as potential substitutes for dairy proteins, due to their suitable functionality and nutritional value. This study was designed to compare the structural and functional responses of different plant protein isolates (soy, pea, lentil, and chickpea) with two commonly used dairy protein (whey protein isolates and sodium caseinate) under different pH treatments (pH 3.0, 5.0, 7.0, and 9.0). The results showed that pH had a different alteration on the structural, surface properties and functional properties of plant and dairy proteins. Plant protein generally possessed a darker color, lower solubility, emulsifying properties, and foaming capacity, whereas their foaming stability and water holding capacity were higher than those of dairy proteins. Soy protein isolates were characterized by its comparable proportion of β-turn and random coils, zeta-potential, emulsifying (30.37 m²/g), and water-holding capacity (9.03 g/g) at alkaline conditions and chickpea protein isolates showed good oil-holding capacity (3.33 g/g at pH 9) among plant proteins. Further analysis confirmed that pH had a greater influence on the structural and functional properties of proteins as compared to protein sources, particularly at acidic conditions. Overall, this study might help processors select the appropriate plant protein as dairy alternatives for their target application in plant-based food products.