Does dextran molecular weight affect the mechanical properties of whey protein/dextran conjugate gels?

The Potency of Maillard Conjugates Containing Whey Protein as Natural Emulsifier

There is a continued need for the advancement of natural emulsifiers to replace synthetic emulsifiers, driven by human health concerns. This study is aimed at producing protein-polysaccharide conjugates through the Maillard reaction and at evaluating its ability as an emulsifier based on its emulsifying properties. The proteins used in this study were bovine milk whey protein and soy protein isolates, while the polysaccharides were maltodextrin and pectin. The protein-polysaccharide conjugation used a Maillard reaction under dry heating conditions. The protein and polysaccharide mass ratios were 1 : 2 and 1 : 3. The results showed that the types of proteins and polysaccharides and their mass affect the surface tension of the conjugate products. Whey protein-pectin conjugates with a mass ratio of 1 : 2 and a concentration of 1% had the lowest surface tension at 43.77 dyne/cm2. This conjugate sample also showed the highest emulsifying index at 27.20 m2/g. The conjugate powder containing pectin as a polysaccharide showed better emulsifying activity than that of those containing maltodextrin. However, the smallest droplet size of the emulsion (256.5 nm) resulted from the emulsification process using whey protein-maltodextrin conjugates as an emulsifier. The FTIR and gel electrophoresis (SDS-PAGE) analysis confirmed the conjugation formation. In general, protein-polysaccharide conjugates containing whey protein could potentially act as a natural emulsifier for food.

Freeze-thaw stability of transglutaminase-induced soy protein-maltose emulsion gel: Focusing on morphology, texture properties, and rheological characteristics

In this study, soy protein isolate (SPI) and maltose (M) were employed as materials for the synthesis of a covalent compound denoted as SPI-M. The emulsion gel was prepared by transglutaminase (TGase) as catalyst, and its freeze-thaw stability was investigated. The occurrence of Maillard reaction was substantiated through SDS-PAGE. The analysis of spectroscopy showed that the structure of the modified protein was more stretched, changed in the direction of freeze-thaw stability. After three freeze-thaw cycles (FTC), it was observed that the water holding capacity of SPI-M, SPI/M mixture (SPI+M) and SPI emulsion gels exhibited reductions of 8.49 %, 16.85 %, and 20.26 %, respectively. Moreover, the soluble protein content also diminished by 13.92 %, 23.43 %, and 35.31 %, respectively. In comparison to unmodified SPI, SPI-M exhibited increase in gel hardness by 160 %, while elasticity, viscosity, chewability, and cohesion demonstrated reductions of 17.7 %, 23.3 %, 33.3 %, and 6.76 %, respectively. Concurrently, the SPI-M emulsion gel exhibited the most rapid gel formation kinetics. After FTCs, the gel elastic modulus (G') and viscosity modulus (G″) of SPI-M emulsion were the largest. DSC analysis underscored the more compact structure and heightened thermal stability of the SPI-M emulsion gel. SEM demonstrated that the SPI-M emulsion gel suffered the least damage following FTCs.

Influence mechanism of polysaccharides induced Maillard reaction on plant proteins structure and functional properties: A review

Plant proteins have high nutritional value, a wide range of sources and low cost. However, it is easily affected by the environmental factors of processing and lead the problem of poor functionality. These problems of plant proteins can be improved by the polysaccharides induced Maillard reaction. The interaction between proteins and polysaccharides through Maillard reaction can change the structure of proteins as well as improve the functional properties and biological activity. The products of Maillard reaction, such as reductone intermediates, heterocyclic compounds and melanoidins have certain antioxidant, antibacterial and other biological activities. However, heterocyclic amines, acrylamide, and products generated in the advanced stage of the Maillard reaction also have a negative impact, which may increase cytotoxicity and be associated with chronic diseases. Therefore, it is necessary to effectively control the process of Maillard reaction. This review focuses on the modification of plant proteins by polysaccharide-induced Maillard reaction and the effects of Maillard reaction on protein structure, functional properties and biological activity. It also points out how to accurately reflect the changes of protein structure in Maillard reaction. In addition, it also points out the application ways of plant protein-polysaccharide complexes in the food industry, for example, emulsifiers, delivery carriers of functional substances, and natural antioxidants due to their improved solubility, emulsifying, gelling and antioxidant properties. This review provides theoretical support for controlling Maillard reaction based on protein structure.

Antioxidant activity and interactions between whey protein and polysaccharides from different parts of Houttuynia cordata

Houttuynia cordata polysaccharides (PSY) are known to exhibit a variety of beneficial activities, but these are currently not specifically utilized in food. Hence, using the two edible parts of Houttuynia cordata, a herbaceous plant native to Southeast Asia, this study developed polysaccharides of a stem (HCPS)-whey protein concentrate (WPC) complex and a leaf (HCPL)-WPC complex, and studied their stability, structure and antioxidant activity. The results showed that stability differed in complexes with different proportions, exhibiting only relative stability in the two complexes in which the ratio of HCPS-WPC and HCPL-WPC was 1:4, but increased stability in the HCPL-WPC complex (ζ-potential of HCPL-WPC: | -21.87 mv| >ζ-potential of HCPS-WPC: | -21.70 mv|). Structural characterization showed that there was electrostatic interaction between HCPS and WPC and between HCPL and WPC. The HCPL-WPC was found to have better antioxidant activity. The findings of this study, thus, provide a reference for the development of Houttuynia cordata polysaccharide applications in food.

Glycated modification of the protein from Rana chensinensis eggs by Millard reaction and its stability analysis in curcumin encapsulated emulsion system

Forest frog (Rana chensinensis) eggs contain high-quality protein but have not been well utilized. In this study, the total protein of forest frog eggs was extracted and 4491 protein/peptides were identified by HPLC-MS/MS. The egg protein was glycated using monosaccharides (lactose, fructose, xylose and glucose). The xylose modified egg protein showed excellent emulsifying ability, high viscosity and uniform structure under the laser confocal microscope in a concentration dependent way (1-3%, w/v). We next used xylose glycated egg protein to encapsulate curcumin to determine the stability of its emulsion system. This emulsion system showed low particle size (< 400 nm) and high Zeta-potential (> 30 mV with absolute value) at pH > 6. The system was stable under 4 °C, 25℃ and 37 °C after seven weeks' storage, especially for the emulsions at 3% and 5% concentrations. Therefore, the glycated frog egg protein can be used to encapsulate hydrophobic nutrients.

Rheological and textural properties of acid-induced soybean protein isolate gel in the presence of soybean protein isolate hydrolysates or their glycosylated products

Enzymatic hydrolysis and glycosylation were successively applied to modify soybean protein isolate (SPI) and rheological and textural properties of acid-induced SPI gel added with the obtained SPI hydrolysates and their glycosylated products were then investigated. The incorporation of SPI hydrolysates decreased the elastic modulus (G') and hardness of SPI gel, which might be related to the random aggregation between SPI hydrolysates and native SPI molecules via hydrophobic interactions. In addition, as the molecular weight of SPI hydrolysates decreased, the reduction in G' and hardness became more significant. Although glycosylation of SPI hydrolysates weakened the adverse effects of hydrolysates on the SPI gel formation to some extent, the glycosylated SPI hydrolysates were still unable to improve the gel quality compared with the control. However, results of this research may provide important information for understanding the influencing mechanism of SPI hydrolysates and their glycosylated products on the formation of SPI gel.

Preparation and characterization of phytosterol-loaded nanoparticles with sodium caseinate/dextran conjugates

Sodium caseinate (SC)/dextran conjugates were prepared via Maillard reaction under controlled dry-heating conditions. Moreover, the nanoparticles of phytosterols (PS) encapsulated by SC or SC/dextran were produced using the emulsion evaporation method. The encapsulation efficiency (78.81 ± 5.22%) of PS in SC/dextran nanoparticles was higher than that (73.5 ± 2.78%) in SC nanoparticles. Compared with the compact and dense structure of SC nanoparticles, SC/dextran nanoparticles existed as relatively loose aggregates. The result of differential scanning calorimetry demonstrated that the encapsulation of PS greatly decreased its crystallinity. The released rates of PS from SC and SC/dextran nanoparticles under acidic gastric conditions were 8.59% and 4.73%, respectively. After 7 h of intestinal digestion, the released rate (52.19%) of PS from SC/dextran nanoparticles was significantly higher than that from SC (32.67%) nanoparticles. Therefore, SC/dextran conjugates prepared by the Maillard reaction are more suitable to be used as wall material for the nano-encapsulation of PS.

Functional and biological properties of Maillard conjugates and their potential application in medical and food: A review

Protein and peptides are usually sensitive to environmental stresses, such as pH changes, high temperature, ionic strength, and digestive enzymes amongst other, which limit their food and medicinal applications. Maillard reaction (also called Maillard conjugation or glycation) occurs naturally without the addition of chemical agents and has been vastly applied to boost protein/peptide/amino acid functionalities and biological properties. Protein/peptide-saccharide conjugates are currently used as emulsifiers, antioxidants, antimicrobials, gelling agents, and anti-browning compounds in food model systems and products. The conjugates also possess the excellent stabilizing ability as a potent delivery system to enhance the stability and bioaccessibility of many bioactive compounds. Carbonyl scavengers such as polyphenols are able to significantly inhibit the formation of advanced glycation end products without a significant effect on early Maillard reaction products (MRPs) and melanoidins, which are currently applied as functional ingredients. This review paper highlights the technological functionality and biological properties of glycoconjugates in food model systems and products. Recent applications of MRPs in medical sciences are also presented.

Dextranol: An inert xeroprotectant

Dextranol, a reduced dextran, prevents damage to stored dry protein samples that unmodified dextran would otherwise cause. Desiccation protectants (xeroprotectants) like the polysaccharide dextran are critical for preserving dried protein samples by forming a rigid glass that protects entrapped protein molecules. Stably dried proteins are important for maintaining critical information in clinical samples like blood serum as well as maintaining activity of biologic drug compounds. However, we found that dextran reacts with both dried serum proteins and lyophilized purified proteins during storage, producing high-molecular weight Amadori-product conjugates. These conjugates appeared in a matter of days or weeks when stored at elevated temperatures (37° or 45°C), but also appeared on a timescale of months when stored at room temperature. We synthesized a less reactive dextranol by reducing dextran's anomeric carbon from an aldehyde to an alcohol. Serum samples dried in a dextranol-based matrix protected the serum proteins from forming high-molecular weight conjugates. The levels of four cancer-related serum biomarkers (prostate specific antigen, neuropilin-1, osteopontin, and matrix-metalloproteinase 7) decreased, as measured by immunoassay, when serum samples were stored for one to two weeks in dextran-based matrix. Switching to a dextranol-based xeroprotection matrix slightly reduced the damage to osteopontin and completely stopped any detectable damage during storage in the other three biomarkers when stored for a period of two weeks at 45°C. We also found that switching from dextran to dextranol in a lyophilization formulation eliminates this unwanted reaction, even at elevated temperatures. Dextranol offers a small and easy modification to dextran that significantly improves the molecule's function as a xeroprotectant by eliminating the potential for damaging protein-polysaccharide conjugation.

Time effect on structural and functional properties of whey protein isolate-gum acacia conjugates prepared via Maillard reaction

BACKGROUND

The functional properties of whey protein isolate (WPI) are sensitive to pH, ionic strength, and temperature. This prevents its application in various food systems and processing technologies. The conjugation of proteins with polysaccharides via the Maillard reaction is an efficient method to improve the functionality of proteins. The purpose of this work was to conjugate gum acacia (GA) with WPI via the dry-heating Maillard reaction and to investigate the effect of reaction time on the physicochemical and functional properties of WPI-GA conjugates.

RESULTS

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-performance size exclusion chromatography confirmed the formation of higher molecular weight conjugates. The degrees of glycation for WPI-GA conjugates incubated for 1, 3, 5, and 7 days were 28.14%, 44.98%, 49.50%, and 51.20%, respectively. The glycation reaction reduced the surface hydrophobicity and fluorescence intensity of WPI significantly (P < 0.05). Functional properties of the conjugates, such as solubility, stability against heat-induced insolubility, and emulsion properties were all superior to the control WPI. However, a reaction time longer than a day resulted in a high degree of browning and decreased the functionality of the conjugate significantly (P < 0.05).

CONCLUSION

The results indicated that conjugation of WPI with GA can be a promising way to enhance its functional properties. However, the reaction time suitable for producing conjugates with superior functional properties was not necessarily the highest glycation degree that could be reached. © 2019 Society of Chemical Industry.

Effects of roasting on composition of chili seed and storage stability of chili seed oil

This work focused on how roasting changed the chemical components of chili (Capsicum annuum L.) seeds and how it affected the stability of chili seed oils during storage. The oils from chili seeds before and after roasting treatments were stored at 63 °C for 30 days and then analyzed. Results showed that roasting changed the main sugars compositions and amino acid compositions (total content decreased from 15.9 to 7.4%), which confirmed that it could form brown pigments and volatile flavor compounds in pepper seeds after roasting. Compared with oil from unroasted seeds, oils from roasted seeds had greater oxidative stability and maintained greater antioxidant capacity during storage. These effects were possibly due to the synergistic of the neo-formed products by Maillard reaction, vitamin E, and other bioactive components. This investigation showed that roasting treatment could be considered as an appropriate method for extending the storage stability of chili seed oils.

Effects of ultrasonic and graft treatments on grafting degree, structure, functionality, and digestibility of rapeseed protein isolate-dextran conjugates

Rapeseed protein isolate (RPI) and dextran conjugates were prepared by traditional and ultrasonic assisted wet-heating. The effects on the grafting degree (GD), structure, functionality, and digestibility of conjugates were studied. Ultrasonic frequency, temperature, and time all significantly affected the GD. Under the optimum conditions (temperature of 90 °C and time of 60 min), compared to traditional wet-heating, ultrasonic treatment at 28 kHz significantly increased the GD by 2.12 times. Compared to RPI, surface hydrophobicities of conjugates were significantly decreased by graft and ultrasonic treatments. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and amino acid composition results confirmed that traditional graft reaction involved cysteine (Cys) and lysine (Lys) whereas the ultrasonic assisted one involved only Cys. Both were from the 12S globulin subunit and cruciferin. Fourier transform infrared spectrum (FT-IR) and circular dichroism (CD) results showed that graft treatment significantly changed secondary structure and ultrasonic treatment had the greatest impact on the decrease in the β-sheet (19.1%) and the increase in the random coil (49.6%). Graft and ultrasonic treatments both made surface structure looser and more porous. The two treatments also caused molecular weight to become bigger, and ultrasonic treatment had the greatest effect on the increase (68.2%) in 110-20.5 kDa. Structural modifications of RPI by grafting to dextran caused improvements of solubility (at pH 5-6), emulsifying activity (at pH 4-10), emulsion stability (at pH 4-5 and 9-10), and thermal stability (at temperature 90-100 °C). The digestibility of conjugates was decreased by graft and ultrasonic treatments and the conjugates were mainly digested in the intestinal phase. The ultrasonic assisted wet-heating was an efficient and safe method for producing RPI-dextran conjugates and improving the utilization value of rapeseed meal.

Glycation of whey proteins: Technological and nutritional implications

Whey proteins are globular proteins that have received much attention due to their high nutritional value and characteristic functional properties. In addition to being part of the protein system in milk, they constitute the main proteins in whey and whey protein products. Interaction of whey proteins with reducing sugars and carbohydrates via Maillard reaction have been extensively studied in milk and in model systems. Glycation of individual whey proteins results in variable increases in their solubility, thermal stability, antioxidant activity, and emulsion and foam stabilization. Limited glycation of whey protein products particularly whey protein isolates (WPI) using polysaccharides has been studied with the aim to produce conjugates with modified functional properties and acceptable sensory properties. An overview is presented here on the effect of glycation on individual whey proteins and whey protein products and the potential uses of the glycated whey proteins.