Property modification of caseinate responsible to transglutaminase-induced glycosylation and crosslinking in the presence of a degraded chitosan

The Formation of Protein-Chitosan Complexes: Their Interaction, Applications, and Challenges

Protein-polysaccharide interactions have been a subject of considerable interest in the field of food science. Chitosan is the most prominent and naturally occurring polysaccharide with a positive charge, and its hydroxyl and amino groups facilitate protein-chitosan interactions due to their diverse biochemical activities. The complexation of chitosan enables the modification of proteins, thereby enhancing their value for applications in the food and nutrition industry. This paper presents a summary of the complexes formed by chitosan and different proteins, such as lactoglobulin, egg white protein, soybean isolate protein, whey isolate protein, and myofibrillar protein, and systematically describes the modes of interaction between proteins and chitosan. The effects of protein-chitosan interactions on functional properties such as solubility, emulsification, antioxidant activity, and stability are outlined, and the potential applications of protein-chitosan complexes are discussed. In addition, the current challenges associated with the formation of protein-chitosan complexes and potential solutions to these challenges are highlighted. This paper provides an overview of the current research progress on the interaction of proteins with chitosan and its derivatives in the food industry.

Transglutaminase-Catalyzed Glycosylation Improved Physicochemical and Functional Properties of Lentinus edodes Protein Fraction

Lentinula edodes has high nutritional value and abundant protein. In order to develop and utilize edible mushroom protein, this study was designed to investigate the effects of TGase-catalyzed glycosylation and cross-linking on the physicochemical and functional properties of Lentinus edodes protein fraction. The results showed that within a certain time, glycosylation and TGase-catalyzed glycosylation decreased the total sulfydryl, free sulfydryl, disulfide bond, surface hydrophobicity, β-fold and α-helix, but increased the fluorescence intensity, random coil, β-turn, particle size and thermal stability. The apparent viscosity and the shear stress of the protein with an increase in shear rate were increased, indicating that TGase-catalyzed glycosylation promoted the generation of cross-linked polymers. In addition, the TGase-catalyzed glycosylated proteins showed a compact texture structure similar to the glycosylated proteins at the beginning, indicating that they formed a stable three-dimensional network structure. The flaky structure of proteins became more and more obvious with time. Moreover, the solubility, emulsification, stability and oil-holding capacity of enzymatic glycosylated Lentinus edodes protein fraction were significantly improved because of the proper TGase effects of glycosylation grafting and cross-linking. These results showed that glycosylation and TGase-catalyzed glycosylation could improve the processing characteristics of the Lentinula edodes protein fraction to varying degrees.

Food protein glycation: A review focusing on stability and in vitro digestive characteristics of oil/water emulsions

Recently, increasing studies have shown that the functional properties of proteins, including emulsifying properties, antioxidant properties, solubility, and thermal stability, can be improved through glycation reaction under controlled reaction conditions. The use of glycated proteins to stabilize hydrophobic active substances and to explore the gastrointestinal fate of the stabilized hydrophobic substances has also become the hot spot. Therefore, in this review, the effects of glycation on the structure and function of food proteins and the physical stability and oxidative stability of protein-stabilized oil/water emulsions were comprehensively summarized and discussed. Also, this review sheds lights on the in vitro digestion characteristics and edible safety of emulsion stabilized by glycated protein. It can further serve as a research basis for understanding the role of structural features in the emulsification and stabilization of glycated proteins, as well as their utilization as emulsifiers in the food industry.

Preparation, characterization and bioavailability studies of Tegillarca granosa hemoglobin and its glycosylated products

Iron deficiency anemia (IDA) is a common micronutrient deficiency. Tegillarca granosa (T. granosa) is a good source of iron due to its high content of hemoglobin. The present study aimed to determine the effects of glycosylation on structure, physicochemical characteristics and iron bioavailability of hemoglobin. Using Box-Behnken design and response surface methodology, the optimal conditions for hemoglobin-chitosan glycosylation were obtained: 61.8 °C, pH 6.3, hemoglobin/chitosan mass ratio of 4.3 and reaction time of 15 min. The formation of hemoglobin-chitosan conjugates was verified by SDS-PAGE and fluorescence spectroscopy. The surface hydrophobicity of hemoglobin was reduced by 20.90-65.05 % after glycosylation, along with the observations of elevated water-holding capacity, likely owing to the introduction of hydrophilic groups. Antioxidant capacity of glycosylated products (0.41-0.66 μM Trolox/mg protein) was markedly greater than that of original protein (0.06 μM Trolox/mg protein) due to the formation of brown polymers with antioxidant activity. In addition, glycosylation improved in vitro digestibility of hemoglobin by 41.15-69.09 %, which could be attributed to less β-sheet in secondary structures. Moreover, hemoglobin (324.38 ng/mg) exhibited better iron absorption than FeSO₄ (121.63 ng/mg), with the value being further enhanced by glycosylation (442.73 ng/mg), which may be due to the improved protein digestibility and iron-chelating capacity.

Limited hydrolysis and conjugation of zein with chitosan oligosaccharide by enzymatic reaction to improve functional properties

In order to improve its aqueous solubility and emulsifying function, zein was partially hydrolyzed by trypsin and conjugated to chitosan oligosaccharide lactate by transglutaminase. Hydrolysis and covalent linkage to chitosan oligosaccharide was confirmed by free amine content, gel electrophoresis, and infrared spectroscopy. Enzymatic glycosylation was optimized at pH 6, 44 °C, and 4 h to bind approximately 95% of the free amines in the hydrolysates to chitosan oligosaccharide. Hydrolysis and conjugation increased solubility of zein by 47.60% and 72.93%. Hydrolysis and conjugation also decreased surface hydrophobicity by more than 20% and more than doubled emulsifying activity index, emulsion stability index, and foaming capacity. This enzymatic modification has potential to be applied to improve functional properties of other prolamins.

Acid-Induced Gelation of Enzymatically and Nonenzymatically Cross-Linked Caseins-Texture Properties, and Microstructural Insights

Casein gels consist of a fractal organized network of aggregated casein particles. The gel texture thereby depends on the structure, the spatial distribution, and the interaction forces of the network's elementary building blocks. The aim of this study was to explore the technofunctional consequences of a possible specificity of Maillard reaction-induced cross-linking reactions on casein with respect to texture and microstructure of acid gels. Therefore, sodium caseinate glycated with lactose in the dry state (60 °C, a_w 0.5) was compared with casein samples cross-linked with methylglyoxal, with glutaraldehyde, or via microbial transglutaminase, respectively, at similar levels of protein cross-linking as confirmed by size-exclusion chromatography under denaturing conditions. Casein gels prepared by acidification with glucono-δ-lactone were characterized concerning pH kinetics during gelation, mechanical texture properties under large deformation, and water-holding capacity, while viscometric properties of casein suspensions were obtained prior to gelation. The gel microstructure was captured by confocal laser scanning microscopy and evaluated by means of image texture analysis. All protein cross-linking reactions studied led to an enhanced gel strength which was accompanied by an increased interconnectivity of the gel network and a decrease in apparent pore sizes. Gels with more densely packed strands, as was the case for enzymatically modified casein, exhibited pronounced mechanical stability. The spontaneous destabilization of the gel network upon prolonged glycation reactions, which was not obviously displayed by microstructural features but connected to an increased viscosity and pronounced pseudoplastic flow of the unacidified suspension, suggests a limitation of particle rearrangements and the weakening of interparticle protein-protein interactions by additional structure attributes formed during the early Maillard reaction (glycoconjugation).

Structure and property changes of the soy protein isolate glycated with maltose in an ionic liquid through the Maillard reaction

An ionic liquid is verified to enhance maltose-glycation and property changes of soy protein isolate through two chemical mechanisms.

Modified properties of a glycated and cross-linked soy protein isolate by transglutaminase and an oligochitosan of 5 kDa

BACKGROUND

Soy protein is an important protein ingredient for the food industry; however, its properties can be improved by enzymatic and chemical modifications. This study applied a new enzymatic glycation and cross-linking to modify soy protein isolate (SPI), using an oligochitosan of 5 kDa and transglutaminase. Properties of the obtained glycated and cross-linked SPI (GC-SPI) were unknown and thus assessed.

RESULTS

GC-SPI contained glucosamine of 13.6 g kg^-1 protein, but less reactable &bond;NH₂ than SPI (0.42 vs. 0.50 mol kg^-1 protein). Infrared spectra and circular dichroism results showed that GC-SPI other than SPI and cross-linked SPI had more &bond;OH in molecules, and was more disordered in secondary structure. In comparison with SPI, GC-SPI showed enhanced water-binding capacity, could form aggregates with enlarged hydrodynamic radius (180.2 vs. 82.9 nm) and negative zeta-potential (-31.2 vs. -27.7 mV) in dispersion, but exhibited lower thermal stability (e.g. greater mass loss) upon heating at a temperature above 288 °C. GC-SPI also had lower in vitro proteolytic digestibility than SPI due to the protein cross-linking.

CONCLUSION

Oligochitosan of 5 kDa and transglutaminase can be used to glycate and cross-link SPI. This approach is applicable to generate potential protein ingredient with good hydration and dispersive stabilisation. © 2016 Society of Chemical Industry.

Pre-deamidation of soy protein isolate exerts impacts on transglutaminase-induced glucosamine glycation and cross-linking as well as properties of the products

BACKGROUND

Transglutaminase (TGase) induces protein glycation and cross-linking, but results in lower solubility and digestibility due to excessive cross-linking. Deamidation of soy protein isolate (SPI) by HCl converts glutamine residues, and provides less opportunity for the two reactions. Two deamidated SPI products (DSPI1 and DSPI2) were thus glucosamine-glycated and cross-linked, to clarify the effects of pre-deamidation on the two reactions and properties of the products.

RESULTS

DSPI1 and DSPI2 had respective degrees of deamidation of 12.2% and 27.4%. They and SPI were used to generate three glycated and cross-linked products (GC-DSPI1, GC-DSPI2 and GC-SPI) containing glucosamine of 12.0, 4.4 and 19.7 g kg(-1) protein, respectively, which were reflected in their infrared spectra at two regions. These three (especially GC-SPI) had higher water-binding than SPI (8.2-12.6 versus 6.2 g g(-1) protein). GC-DSPI1 and GC-DSPI2 showed better enzymatic digestion than GC-SPI. Thermogravimetric and circular dichroism analyses verified that GC-DSPI1 and GC-DSPI2 had maximum degradation rates at temperatures 12-14 °C lower than GC-SPI, and possessed a more open secondary structure.

CONCLUSION

SPI deamidation decreases forthcoming glycation and cross-linking, and gives the products higher digestibility, less increased hydration, lower thermal stability, and a more open secondary structure. Pre-deamidation is applicable to control the properties of GC-proteins. © 2015 Society of Chemical Industry.