Influence of glycation extent on the physicochemical and gelling properties of soybean β-conglycinin

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.

Study on functional improvement of freeze-thaw egg yolk pellet by enzymatic hydrolysis

Freeze-thaw egg yolk pellet (FYP) could be produced as a by-product in the process of egg yolk immunoglobulin (IgY) extraction. The FYP contained many superior nutritional components like fresh egg yolk, but it has poor functionalities because of protein denaturation resulted from freezing treatment during IgY extraction. For the purpose of comprehensive utilization of egg yolk resources, FYP was subjected to enzymatic hydrolysis with alcalase to produce FYP hydrolysates (FYPh) with four enzyme concentrations of 250, 500, 1000 and 2000 U/g for improved functional properties. And then FYPh was spray dried to obtain hydrolyzed egg yolk pellet powder (HYP). Solubility, emulsifying property and surface hydrophobicity of HYP were investigated. The results showed that enzymatic hydrolysis could lead to noticeable changes in surface hydrophobicity, microstructure, solubility and emulsifying properties of HYP compared with the control group without enzymatic hydrolysis treatment. Solubility and emulsification stability index generally increased from 19 g/100 g, 12.33 to 87 g/100 g, 76.63 with increasing degree of hydrolyze, respectively. This study demonstrated that the functional properties of FYP could be effectively improved when the enzyme addition amount reached 1000 U/g. HYP prepared under this condition owes desirable solubility and emulsification, and has the potential of application in food industry.

Structural and emulsifying properties of soybean protein isolate glycated with glucose based on pH treatment

BACKGROUNDS

In the present study, a glycosylated soybean protein with glucose was prepared after pH treatment under different conditions (5.0, 6.0 7.0, 8.0, 9.0) and the conformation and emulsifying properties of soybean protein isolate (SPI) and soybean protein isolate-glucose (SPI-G) were investigated.

RESULTS

The degree of grafting (37.11%) and browning (39.2%) of SPI-G conjugates were obtained at pH 9.0 (P < 0.05). The results of analysis of polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy and Endogenous fluorescence spectroscopy showed that the Maillard reaction between the SPI and glucose occurred and the natural rigid structure of test proteins was stretched and became looser, and thus the tertiary conformation was unfolding. Furthermore, the particle size of the all of samples was reduced under different pH conditions, indicating that pH treatment can increase the flexibility of SPI molecules. The proteins exhibited the best surface hydrophobicity, thermal stability and emulsifying activity (EA) of modified products when subjected to a pH treatment of 9.0, whereas they afforded the best emulsion stability (ES) at pH 8.0. There was a good correlation between the molecular flexibility and emulsifying properties of SPI-G [0.963 (F:EA) and 0.879 (F:ES)] (P < 0.05).

CONCLUSION

The present study shows that the structural and emulsification characteristics of natural SPI and SPI-G conjugates have been significantly enhanced via pH treatment and these results provide a theoretical guidance for the application of glycosylated SPI in the food industry. © 2022 Society of Chemical Industry.

Glycation of Plant Proteins Via Maillard Reaction: Reaction Chemistry, Technofunctional Properties, and Potential Food Application

Plant proteins are being considered to become the most important protein source of the future, and to do so, they must be able to replace the animal-derived proteins currently in use as techno-functional food ingredients. This poses challenges because plant proteins are oftentimes storage proteins with a high molecular weight and low water solubility. One promising approach to overcome these limitations is the glycation of plant proteins. The covalent bonding between the proteins and different carbohydrates created via the initial stage of the Maillard reaction can improve the techno-functional characteristics of these proteins without the involvement of potentially toxic chemicals. However, compared to studies with animal-derived proteins, glycation studies on plant proteins are currently still underrepresented in literature. This review provides an overview of the existing studies on the glycation of the major groups of plant proteins with different carbohydrates using different preparation methods. Emphasis is put on the reaction conditions used for glycation as well as the modifications to physicochemical properties and techno-functionality. Different applications of these glycated plant proteins in emulsions, foams, films, and encapsulation systems are introduced. Another focus lies on the reaction chemistry of the Maillard reaction and ways to harness it for controlled glycation and to limit the formation of undesired advanced glycation products. Finally, challenges related to the controlled glycation of plant proteins to improve their properties are discussed.

Effect of Soybean Soluble Polysaccharide on the Formation of Glucono-δ-Lactone-Induced Soybean Protein Isolate Gel

The effect of soybean soluble polysaccharide (SSPS) on the formation of glucono-δ-lactone (GDL)-induced soybean protein isolate (SPI) gel was investigated. Electrophoretic analysis showed the SSPS did not change the electrophoretic behavior of SPI during the formation of SPI gel. However, infrared analysis indicated the β-sheet content increased, and the contents of random coil and α-helix decreased in both cooked SPI and SPI gel. The SSPS and SPI might conjugate via the Maillard reaction according to the results of grafting degree, color change, and infrared analyses. The main interactions during the formation of SPI gel changed from non-covalent to electrostatic interaction after adding SSPS. Sulfhydryl group content also increased in both cooked SPI and SPI gel. The water-holding capacity and gel strength of SPI gel decreased as the SSPS concentration increased. Larger aggregate holes were observed in the microstructure of SPI gel at higher SSPS concentration. Thus, SSPS could covalently conjugate with SPI and influence the formation of hydrogen bonds, disulfide bonds, and electrostatic interaction among SPI molecules to eventually form a loose gel network.

Study on structural, rheological and foaming properties of ovalbumin by ultrasound-assisted glycation with xylose

This study was to evaluate the effect of ultrasound-assisted glycation with xylose on the foaming properties, physicochemical and structural characteristics of ovalbumin (OVA). The number of free amino groups in the glycated OVA (sOVA-X) significantly decreased with the increase of treatment time. The results obtained by circular dichroism (CD) and spectrofluorimetric measurements showed that there were slight changes on the subunits and secondary structure of OVA, indicating that the tertiary structure became more flexible and loose after the sonicated glycation treatment. The glycated OVA had higher solubility and foaming properties than the untreated samples. Therefore, ultrasound improved the glycation extent, and the changes in molecular structure were responsible for their different foaming ability and foaming stability. Our study also provided principle knowledge to understand how the viscosity and rheology were related to the foaming properties of OVA glycation by xylose. The results indicated that ultrasound-assisted glycation could be an excellent approach to improve the functional properties of OVA and promote its application in food industry.

Formation of amyloid fibrils from soy protein hydrolysate: Effects of selective proteolysis on β-conglycinin

The soy protein hydrolysate subjected to selective proteolysis on β-conglycinin (referred to as DβH, contrast group) and a control soy protein isolate sample without addition of protease (referred to as CSPI, blank group) were adopted as experimental samples. By employing the "subtraction" mode of logical thinking, we aimed to compare the differences between CSPI and DβH on fibrillation at pH2.0 with heating at 95°C. The results showed when heated for 60min, CSPI tended to form short worm-like fibrils while DβH long semiflexible fibrils. When heating time was prolonged to 360min, the fibrils formed from them both exhibited cluster. Whereas when heated for 720min, no fibrillar aggregates appeared from them. This study would help explore the effects of β-conglycinin on the fibril formation of soy protein isolate by a new way.

Chemical characterization of the glycated myofibrillar proteins from grass carp (Ctenopharyngodon idella) and their impacts on the human gut microbiota in vitro fermentation

Glycation greatly increased the anti-digestibility of myofibrillar proteins derived from grass carp, and affected the production of SCFAs and the microbial community structures inin vitrofecal fermentation.