Enhanced bactericidal action and masking of allergen structure of soy protein by attachment of chitosan through maillard-type protein-polysaccharide conjugation

The soy protein-chitosan conjugate was formed by the Maillard reaction in dry state (relative humidity 65%) at 60 degrees C for 2 weeks to improve the functional properties. The antimicrobial activity of the Maillard-type soy protein-chitosan conjugates enhanced 2-3 times that of soy protein-chitosan mixture. The soy protein-chitosan conjugate showed excellent emulsifying property with the progress of Maillard-type conjugation. The allergenicity of soy protein was greatly decreased by the attachment of chitosan through Maillard reaction. The immonoblotting analysis with patient's sera revealed that soy protein-chitosan conjugate was more effective to mask the allergen structure of soy protein causing from 34 kDa-protein (Gly m Bd 30K) than soy protein-galactomannan conjugate. The Western blotting showed that allergen (34 kDa-protein) was completely masked by soy protein-chitosan conjugation, while it was not completely masked by soy protein-galactomannan conjugation.     

Physicochemical properties and emulsion stabilization of rice dreg glutelin conjugated with κ‐carrageenan through Maillard reaction

BACKGROUND: Rice dreg is an underutilized source of cereal protein with good potential for application in the food industry. Glutelin represents about 850 g kg^?1 of total storage protein in rice dreg. The objective of this study was to characterize the physicochemical properties and emulsion stabilization of the Maillard type conjugate formed with rice dreg glutelin (RDG) and κ‐carrageenan (1:2 weight ratio) dry‐heated at 60 °C and 79% relative humidity for 24 h. RESULTS: Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and Fourier transform‐infrared analysis provided evidence on the formation of the Maillard type conjugation. Amino acid analysis suggested that the major locus during the Maillard reaction were lysine and arginine. Circular dichroism spectra showed decreasing amounts of α‐helix and β‐strand in the products with increment in the amount of turns and random coil. Conjugation with κ‐carrageenan could significantly improve solubility of RDG (P < 0.05). Measurements of mean droplet size and creaming stability in oil‐in‐water emulsions showed that the conjugate was more effective at stabilizing emulsions at low pH or in the presence of high ionic strength. CONCLUSION: The Maillard reaction can be successfully used as a coupling method for RDG and κ‐carrageenan to form the conjugate with improved solubility and emulsion stabilization. Copyright © 2012 Society of Chemical Industry     

Improving Functional Properties of Soy Protein Hydrolysate by Conjugation with Curdlan

ABSTRACT:  Soy protein hydrolysate was conjugated with curdlan through the naturally occurring Maillard reaction to extend its application in food processing. The gel-forming and emulsifying properties of soy protein hydrolysates were significantly improved ( P < 0.05) by conjugation with curdlan. The soy protein hydrolysate–curdlan conjugate (SPHCC)–soy protein isolate (SPI) mixed gel had a much thicker network than the soy protein hydrolysate and SPI mixed gel judged from scanning electron microscopic images. The improvement of gelling properties of soy protein hydrolysate by curdlan-conjugate was attributed to both the decrease in the repulsive forces among soy protein hydrolysates and the increase in the solubility. The covalent binding of soy protein hydrolysates and curdlan also showed a profound effect on the antioxidative activity of the soy protein hydrolysates. The higher antioxidative activity of SPHCC was related to the peptide reductants produced from the Maillard reaction and the higher emulsifying property of SPHCC. The conjugates of soy protein hydrolysate and curdlan can be used as a functional food additive having excellent gel-forming, emulsifying properties and antioxidative activity.     

Multi‐functional biopolymer prepared by covalent attachment of galactomannan to egg‐white proteins through naturally occurring Maillard reaction

Protein‐polysaccharide conjugate was prepared as a functional biopolymer using protein and polysaccharide via a Maillard‐type reaction. Ovalbumin and lysozyme were conjugated with galactomannan under controlled heating and humidity conditions. The antioxidant effect of ovalbumin and the antimicrobial activity of lysozyme were enhanced by the glycosylation. The emulsifying properties of the egg protein were also significantly improved by the modification. The increase in lipid affinity due to the conjugation resulted in the enhancement of the radical scavenging ability of ovalbumin. The effectiveness of lysozyme and its glycosylated derivative in restricting the activity of a Gram‐negative pathogen,Edwardsiella tarda in fish was also investigated.     

Changes in the chemical composition of traditional Chinese‐type soy sauce at different stages of manufacture and its relation to taste

Chemical composition of traditional Chinese‐type soy sauce (TCSS) at different stages of manufacture (moromi fermentation and pasteurisation) were analysed. Results showed that total nitrogen, formaldehyde nitrogen, total titratable acid, reducing sugar, NaCl, water soluble peptides, free amino acids (FAAs) and Maillard reaction products in TCSS changed significantly during manufacture. Most of FAAs were released during initial stage (0–15 days) of moromi fermentation, peptides (1–5 kDa) kept dominant (69.34–80.88%) among all peptides during manufacture and Maillard reaction products increased progressively during moromi fermentation and increased sharply during pasteurisation. According to hierarchical cluster analysis and sensory evaluation, there were obvious correlation between FAAs and sensory score of over‐all in TCSS during manufacture, which indicated that balanced FAAs composition might be mainly responsible for the taste formation of TCSS. Besides, pasteurisation can further improve the over‐all taste of TCSS.     

An Enhanced Stability Nanoparticle Preparation by Corn Protein Hydrolysate‐Carboxymethyl Chitosan Maillard Conjugates Loaded with Rutin

Rutin‐loaded corn protein hydrolysate–carboxymethyl chitosan (CPH‐NOCC) Maillard conjugate nanoparticles (NPs) with superior stability under different NaCl concentrations (0–0.25 mol/L) and pH levels (7.0 to 3.0) were investigated. Results showed that the degree of glycosylation of 53.3%, browning index of 0.6, and SDS‐PAGE lane of CPH‐NOCC conjugates were obtained after dry heating for 48 hr (60 °C, 79% RH). The high encapsulation efficiency (EE, 97.8%–98.8%) and CPH‐NOCC‐rutin (98.8%) was significantly higher than CPH‐rutin (97.8%) and CPH/NOCC‐rutin (98.4%) NPs illustrated that hydrolysis was positive for zein encapsulation, and conjugation of NOCC to CPH increased the EE. Hairy carbohydrate protrusions on the surface of CPH‐NOCC‐rutin NPs produced a stronger steric effect and hampered the formation of salt bridges and the particle aggregation under CPH isoelectric point at pH 4.0. Therefore, the CPH‐NOCC conjugate NPs may be suitable carrier for hydrophobic bioactive substances in a board range of business foodstuffs.     

Formation of acid‐precipitated soy protein–dextran conjugates by Maillard reaction in liquid systems

The conjugation reaction between soybean acid‐precipitated protein (SAPP) and dextran in liquid systems via the initial stage of the Maillard reaction was studied. Functional SAPP–dextran conjugates were prepared in 80% ethanol‐reacting system at 50 °C for 6 h, along with 95% ethanol‐reacting system at 60 °C for 24 h. The covalent attachment of dextran to SAPP was confirmed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and gel filtration chromatography.Compared to the classical dry‐heating, the reaction time of glycosylation in the two ethanol systems was largely shortened. Emulsifying activity of SAPP–dextran conjugates obtained by dry‐heating incubation and in ethanol was similar at pH 7.0 and10.0, significantly higher than that of SAPP–dextran mixture or SAPP alone. In addition, SAPP–dextran conjugates obtained in 80% ethanol‐reacting system for 6 h were completely soluble after heating at 90 °C for 20 min. The impact of various processing conditions on the formation of SAPP–dextran conjugates was investigated. This study provides important guidance to create protein–polysaccharide conjugates at mild temperatures in liquid systems.     

Impact of dextran conjugation on physicochemical and gelling properties of sweet potato protein through Maillard reaction

Covalently linked sweet potato protein (SPP)–dextran conjugates were produced through Maillard reaction, and the effects of this conjugation on physicochemical and gelling properties of SPP were studied. Formation of SPP–dextran-conjugated product was confirmed with increase in browning intensity and molecular weight, with concomitant reduction in free amino group content of the protein. Dry-heating period of 0, 1, 3, 5 and 7 days gave rise to 0%, 12.8%, 19.0%, 25.2% and 22.8% degree of conjugation (DC), respectively. High molecular weight protein polymer with polydispersed band above 50 kDa was formed. FTIR spectroscopic analysis showed that the C-O (amide I) and C-N (amide II) stretching bands were modified by the Maillard reaction. Conjugation of SPP with dextran reduced its denaturation temperature. SPP–dextran conjugate gels’ network structures were sustained by both physical interactions and covalent bonds. SPP–dextran conjugates’ gels had significantly improved hardness and resilience in comparison with the unmodified SPP (P < 0.05).     

Improvement of functional properties of acid-precipitated soy protein by the attachment of dextran through Maillard reaction

The functional acid-precipitated soy protein (SAPP)–dextran conjugate was prepared by dry-heated storage at 60 °C under 79% relative humidity (RH) for 5 days through Maillard reaction between the ε-amino of lysine in soy proteins and the reducing-end carbonyl residue in the dextran. The covalent attachment of dextran to SAPP was confirmed by SDS-polyacrylamide gel electrophoresis and gel filtration chromatography. Functional properties of soy protein depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S). The conjugate seemed to be predominantly formed by 7S, and the acidic subunits of 11S in soy protein. The emulsifying properties of the SAPP–dextran conjugate were about four times higher than those of SAPP. The solubility of the protein was not enhanced as a result of preheating, but rather it was not decreased when the conjugated protein was heated at 90 °C for 20 min due to the presence of the polysaccharide. The excellent emulsifying properties of SAPP–dextran conjugate were maintained even at pH 3.0 and were further improved at pH 10.0. The object of Maillard reaction is to guarantee the suitable reaction degree, and the resulting soluble conjugate can have excellent emulsifying properties.     

Interface-related attributes of the Maillard reaction-born glycoproteins

Interfacial behavior of proteins which is a chief parameter to their emulsifying and foaming properties can be tailored through the Maillard reaction. The reaction can increase protein solubility at isoelectric point and ought to be controlled for example by high pressure processing to suppress melanoidins formation. Branched and long saccharides bring considerable steric hindrance which is associated with their site of conjugation to proteins. Conjugation with high molecular weight polysaccharides (such as 440 kDa dextran) may indeed increase the thickness of globular proteins interfacial film up to approximately 25 nm. However, an overly long saccharide can shield protein charge and slow down the electrophoretic mobility of conjugate. Maillard conjugation may decrease the diffusion rate of proteins to interface, allowing further unfolding at interface. As well, it can increase desorption iteration of proteins from interface. In addition to tempering proteins adsorption to interface, Maillard conjugation influences the rheology of protein membranes. Oligosaccharides (especially at higher glycation degrees) decrease the elastic modulus and Huggins constant of protein film; whereas, monosaccharides yield a more elastic interface. Accordingly, glycation of random coil proteins has been exploited to stiffen the corresponding interfacial membrane. Partial hydrolysis of proteins accompanied with anti-solvent-triggered nanoparticulation either before or after conjugation is a feasible way to enhance their emulsifying activity.     

蛋白-多糖复合物的制备及乳化性能的研究

本文对大豆分离蛋白和多糖共价键合制备反应及其产物的乳化性能进行了初步研究.在60℃,79%相对湿度的条件下两种大分子通过Maillard反应进行共价键合,其产物具有比大豆分离蛋白更高的对油/水乳状液的乳化能力。结果表明,复合物在pH3.0 以及pH10时保持好的乳化活性,并且在高温、高盐条件下乳化活性进一步提高。并通过聚丙烯酰胺凝胶电泳验证了大分子复合物的存在。     

Preparation,characterisation and selected functional properties of hydrolysed sodium caseinate–maltodextrin conjugate

Sodium caseinate was hydrolysed to a limited, moderate or extensive degree. The hydrolysates were conjugated with maltodextrin by a Maillard‐type reaction by dry‐heat treatment at 60 °C and 79% relative humidity for 2 or 4 days. Conjugates were characterised by SDS–PAGE and gel permeation chromatography. In comparison with the hydrolysates themselves, the conjugated hydrolysates had improved solubility, particularly around the isoelectric pH of the protein. The emulsifying properties of these conjugates were assessed in oil‐in‐water (o/w) emulsions; on emulsion formation, each conjugate‐stabilised emulsion had lower mean fat globule size than the corresponding hydrolysate‐stabilised emulsion. After storage for 7 days under accelerated shelf life testing conditions, the limited and moderate hydrolysate conjugate–stabilised emulsions had improved storage stability compared with hydrolysate‐stabilised emulsions; however, further research is required to optimise the hydrolysate fraction prior to conjugation for the production of novel low molecular weight emulsifiers.     

乳清分离蛋白与壳聚糖美拉德反应初级阶段产物乳化性研究

采用干热美拉德反应制备乳清分离蛋白(WPI)-壳聚糖复合物,通过对复合物的乳液粒径及稳定性分析,研究反应温度、WPI与壳聚糖质量比及反应时间对复合物乳化性的影响。荧光光谱分析表明：WPI和壳聚糖在干热反应后发生共价交联并且结构发生了变化。WPI与壳聚糖在50℃、相对湿度79%干热条件下,反应1～4d的产物为Maillard反应初级阶段产物,该产物的乳化性质得到改善。其中,WPI与壳聚糖以质量比1:4混合,50℃反应1d的产物乳化稳定性是反应前的10倍。     

Effect of chitosan conjugation on the functional properties and bactericidal activity of gluten peptides

Gluten was solubilized by chymotrypsin and the soluble peptides were purified and conjugated with chitosans of different degrees of polymerization through the Maillard reaction. High molecular weight-type chitosan (HMC) was found to be soluble at acidic pH and least soluble at neutral pH. However, after conjugation with gluten peptides, its solubility considerably improved at neutral pH while low molecular weight-type chitosan (LMC) conjugates were found to be soluble at both pHs. The emulsifying activity and emulsion stability of HMC conjugate were greatly improved at acidic pH compared to that of LMC. On the other hand, LMC conjugation slightly improved the emulsifying activity of gluten peptides at neutral pH compared to that of HMC. Despite its great efficiency in inhibiting the growth of Escherichia coli cells at high temperature, HMC conjugated with gluten peptides inhibited the growth of the bacterium cells, even at low temperature, significantly better than LMC conjugate.     

Influence of Maillard reaction conditions on the antigenicity of bovine α‐lactalbumin using response surface methodology

BACKGROUND: Maillard reaction can modify functional properties of proteins. Bovine α‐lactalbumin (α‐LA) is often supplemented to the new generation of infant formulae, but it is considered to be a main allergen. However, there is little information on the effect of Maillard reaction on α‐LA antigenicity. The objective of this study was to investigate the influence of Maillard reaction on the antigenicity of α‐LA in conjugates of whey protein isolate (WPI) with glucose under different conditions of protein/sugar weight ratio (0.17–7.83), temperature (40–60 °C) and time (24–120 h) using response surface methodology. RESULTS: Conjugation of WPI with glucose markedly reduced the antigenicity of α‐LA. This reduction in antigenicity could be controlled by regulating the three independent variables weight ratio, temperature and time. A model of optimal reaction conditions for lower antigenicity of α‐LA was established. According to the model, the minimum antigenicity of α‐LA was achieved at 52.8 °C, 78 h and 5.96:1 WPI/glucose weight ratio. WPI/glucose weight ratio had the greatest effect on the antigenicity of α‐LA, while reaction temperature influenced α‐LA antigenicity to a lesser extent. CONCLUSION: Well‐controlled Maillard reaction between WPI and glucose is an efficient method to reduce α‐LA antigencity. Copyright © 2009 Society of Chemical Industry     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Antioxidant and tyrosinase inhibitory activities of a novel chitosan–phloroglucinol conjugate

A novel chitosan–phloroglucinol conjugate was developed by conjugating phloroglucinol onto a chitosan backbone. The chitosan–phloroglucinol conjugate was characterised by ¹H nuclear magnetic resonance (NMR), and the NMR spectra confirmed the conjugation. Antioxidant and tyrosinase inhibitory activities of the chitosan–phloroglucinol conjugate were investigated. The chitosan–phloroglucinol conjugate showed strong 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), hydrogen peroxide and ABTS⁺ radical scavenging activities as well as reducing power compared with those of the unmodified chitosan (P < 0.05). The formation of malondiadehyde (MDA) as an indicator of lipid peroxidation in a linoleic acid emulsion was 30.56 μM in the absence of the chitosan–phloroglucinol conjugate after 4 days incubation, whereas MDA was 4.14 μM in the presence of the chitosan–phloroglucinol conjugate (P < 0.05). The activity was higher than that of ascorbic acid, which is currently used as a food preservative. Moreover, the chitosan–phloroglucinol conjugate inhibited 56.30% tyrosinase activity, which is responsible for browning of foods, and acted as non‐competitive inhibitor. Taken together, the chitosan–phloroglucinol conjugate may have potential for application in functional foods and/or as a food preservative.     

Ultrasound assisted vis-à-vis classical heating for the conjugation of whey protein isolate-gellan gum: Process optimization,structural characterization and physico-functional evaluation

In the present work, ultrasonic assisted synthesis and characterization of Maillard conjugates of whey protein isolate (WPI) and gellan gum (GG) was carried out and compared with the classical heating method. Conjugation was confirmed by FTIR, secondary structure, intrinsic fluorescence analysis, and degree of glycation (DG). The structural analysis revealed high protein unfolding by sonication confirming loss of α-helix content and exposing more amino groups to the conjugation reaction. Color change analysis confirmed that ultrasonication accelerated the initial stage of Maillard reaction but did not form the advanced Maillard reaction products. Ultrasonication gave higher DG in lesser time (17.22% in 60 min) than classical heating method (8.41% in 4 h). Physico-functional properties such as pH and thermal stability, emulsifying activity index, emulsion stability index, foaming capability and antioxidant activity of WPI-GG conjugates prepared by ultrasonic treatment were superior to classical heating method suggesting ultrasonication as a potentially alternative method for Maillard conjugation.Industrial relevanceImprovising supplementary protein functionality by conjugation with food grade polysaccharides like gellan gum through ultrasonication could make the process more controllable and economical. The undesired browning can be inhibited in ultrasonic assisted conjugate synthesis and hence the overall acceptance of the final product can be increased.     

Effect of Molecular Weight,Acid, and Plasticizer on the Physicochemical and Antibacterial Properties of β‐Chitosan Based Films

Abstract: Effects of chitosan molecular weight (1815 and 366 kDa), type of acid (1% acetic, formic, and propionic acid, or 0.5% lactic acid) and plasticizer (0, 25% glycerol or sorbital w/w chitosan) on the mechanical, water barrier, and antibacterial properties of β‐chitosan films were investigated. Tensile strength (TS) of high molecular weight (Hw) films was 53% higher than that of low molecular weight (Lw) ones, acetate, and propionate films had the highest TS (43 and 40 MPa) among tested acids, and plasticizer‐reduced film TS 34%. Film elongation at break (EL) was higher in Hw films than in Lw ones, in which formate and acetate films were the highest (9% and 8%, respectively), and plasticizer increased the film EL 128%. Molecular weight of chitosan did not influence water vapor permeability (WVP) of the films. Acetate and propionate films had lower WVP than other acid types of films, and plasticizer increased film WVP about 35%. No difference was found between glycerol and sorbitol films in terms of film mechanical and water barrier properties. Lw β‐chitosan films showed significant antibacterial activity against E. coli and L. innocua. This study demonstrated that β‐chitosan films are compatible to α‐chitosan films in physicochemical properties and antibacterial activity, yet with simple sample preparation. Practical Application: β‐chitosan based edible films at molecular weight of about 300 kDa showed great antibacterial activity against Gram‐positive and Gram‐negative bacteria. The films have similar mechanical and water barrier properties to α‐chitosan based films at the similar molecular weight, but simple sample preparation procedures and more attractive color. The release of active chitosan fragment from the film matrix acts as an antibacterial agent, making β‐chitosan films suitable as intelligent food wraps or coatings for a wide range of food products to control moisture loss and prevent surface bacterial growth.     

Selected Quality Characteristics of Fresh‐Cut Sweet Potatoes Coated with Chitosan during 17‐Day Refrigerated Storage

ABSTRACT: Selected quality characteristics of fresh‐cut sweet potatoes (FCSP) coated with chitosan were evaluated during 17‐d refrigerated storage. The FCSP cubes were coated with a solution (1%, w/v) of chitosan having 470 or 1110 kDa. Color (L*, a*, b*) values of uncoated and chitosan‐coated FCSP during storage were generally affected by storage time as well as coating treatments (P < 0.05). No significant changes in color lightness (L*) of 470 kDa‐coated FCSP were observed during the 17‐d storage. During days 3 to 17, 470 kDa‐coated FCSP had significantly higher redness (a*) and yellowness (b*) values than did uncoated and 1110 kDa‐coated FCSP. Texture firmness of uncoated and chitosan‐coated FCSP exhibited minimal changes during the 17‐d storage. Although actual weight loss values (%) of uncoated and chitosan‐coated FCSP were not significantly different at day 17, the weight loss difference (%) between day 3 and day 17 for uncoated FCSP (3.02%) was slightly higher compared to those (2.24% to 2.26%) of chitosan‐coated FCSP. The initial total aerobic count was 4.7 log₁₀ CFU/g which then gradually increased to 8.54 and 9.67 log₁₀ CFU/g after 17 d of storage for 470 kDa‐coated and uncoated FCSP, respectively. After day 6, the total aerobic counts of uncoated FCSP were higher than those of 470 kDa‐coated FCSP. The yeast and mold count of chitosan‐coated FCSP was about 2.5 log₁₀ CFU/g at day 17. Overall, consumers could not differentiate between 470 kDa‐coated FCSP at day 17 and uncoated FCSP at day 0.