Effect of milk protein glycation and gastrointestinal digestion on the growth of bifidobacteria and lactic acid bacteria

In this paper, β-lactoglobulin (β-Lg) and sodium caseinate (SC) have been glycated via Maillard reaction with galactose and lactose and, subsequently, the effect of glycoconjugates hydrolyzed under simulated gastrointestinal digestion on the growth of pure culture of Lactobacillus, Streptococcus and Bifidobacterium has been investigated. Glycopeptides were added to the growth media as the sole carbon source. None of the bacterial strains was able to grow in hydrolysates of native and control heated β-Lg and SC. However, glycopeptides were fermented, in different degree, by Lactobacillus and Bifidobacterium and hardly any effect was detected on the growth of Streptococcus. Digested β-Lg glycoconjugates showed a strain-dependent effect whereas growth profiles of bacteria when hydrolysates of SC glycoconjugates were used as substrates were very similar, regardless of the strain. A general preference towards peptides from β-Lg/SC glycated with galactose, particularly at the state of the reaction in which the highest content in the Amadori compound tagatosyl-lysine is present, was observed. SC glycoconjugates were quickly fermented by some strains, promoting their growth in a greater extent than β-Lg complexes or even glucose. Therefore, from the results obtained in this work it can be concluded that conjugation of both milk proteins with galactose and lactose via the Maillard reaction could be an efficient method to obtain novel food ingredients with a potential prebiotic character.     

Functional properties of caseinate glycoconjugates prepared by controlled heating in the ‘dry’ state

Glucose, ribose, fructose, lactose, fructo‐oligosaccharide (inulin) and a mixture of inulin and fructose were conjugated with caseinate via the Maillard reaction using controlled heating and low water activity conditions in order to improve the functional properties of caseinate for food purposes. Conjugation with ribose and glucose increased the viscosity of caseinate 28‐fold over that of the unmodified caseinate control but also produced the most browning. Glycoconjugates of caseinate–fructose reacted at a substrate ratio of 1:0.2 w/w and 60 °C at 67% relative humidity for 48 h increased the viscosity of caseinate 24‐fold with less browning. At 80% relative humidity the reaction occurred so rapidly that, within 24 h gels containing darkly coloured particulate matter were produced. Incorporation of inulin at 1:1:0.2 w/w/w caseinate/inulin/fructose prevented formation of gels and produced glycoconjugates having 15‐fold the viscosity of unmodified caseinate with minimal browning. Copyright © 2005 Society of Chemical Industry     

酪蛋白酸钠美拉德反应产物的制备及其乳化特性

利用小型超高温设备制备酪蛋白酸钠与葡萄糖、乳糖、低聚半乳糖、聚葡萄糖的美拉德反应产物,对比分析不同分子质量糖在不同热处理时间的美拉德反应进程及产物的乳化特性。结果表明,小分子质量的糖更易发生美拉德反应,褐变指数与反应程度呈正相关,乳化活性与接枝度均呈现先增大后减小的趋势,但两者并不成线性关系,酪蛋白酸钠与葡萄糖、乳糖、低聚半乳糖、聚葡萄糖乳化活性达到的最大值分别为0.63、0.51、0.55和0.48,其中130?℃热处理15?s的酪蛋白酸钠-葡萄糖溶液乳化活性最大,高于其他组,与水浴90?℃热处理90?min相当,并且乳化稳定性也呈现较高的水平,为123.88?min,将其用作乳化剂制备的DHA藻油乳状液稳定性动力学指数为1.5,显著小于其他组（P＜0.05）;由此可见,葡萄糖可作为美拉德反应的优良糖基配体制备新型高效的乳化剂,并且此方法可实现连续化生产,极大缩短了反应时间,提高了生产效率,对工业化生产具有指导意义。     

The dual effects of Maillard reaction and enzymatic hydrolysis on the antioxidant activity of milk proteins

The objective of this study was to determine the enhanced effects on the biological characteristics and antioxidant activity of milk proteins by the combination of the Maillard reaction and enzymatic hydrolysis. Maillard reaction products were obtained from milk protein preparations, such as whey protein concentrates and sodium caseinate with lactose, by heating at 55°C for 7 d in sodium phosphate buffer (pH 7.4). The Maillard reaction products, along with untreated milk proteins as controls, were hydrolyzed for 0 to 3 h with commercial proteases Alcalase, Neutrase, Protamex, and Flavorzyme (Novozymes, Bagsværd, Denmark). The antioxidant activity of hydrolyzed Maillard reaction products was determined by reaction with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, their 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and the ability to reduce ferric ions. Further characteristics were evaluated by the o-phthaldialdehyde method and sodium dodecyl sulfate-PAGE. The degree of hydrolysis gradually increased in a time-dependent manner, with the Alcalase-treated Maillard reaction products being the most highly hydrolyzed. Radical scavenging activities and reducing ability of hydrolyzed Maillard reaction products increased with increasing hydrolysis time. The combined products of enzymatic hydrolysis and Maillard reaction showed significantly greater antioxidant activity than did hydrolysates or Maillard reaction products alone. The hydrolyzed Maillard reaction products generated by Alcalase showed significantly higher antioxidant activity when compared with the other protease products and the antioxidant activity was higher for the whey protein concentrate groups than for the sodium caseinate groups. These findings indicate that Maillard reaction products, coupled with enzymatic hydrolysis, could act as potential antioxidants in the pharmaceutical, food, and dairy industries.     

Maillard-type glycoconjugates from dairy proteins inhibit adhesion of Escherichia coli to mucin

In this study, glycoconjugates of β-lactoglobulin (β-Lg) and sodium caseinate (SC) were obtained via Maillard reaction with galactose and lactose, and their ability to inhibit the adhesion of different Escherichia coli strains (CBL2, CBM1 and CBL8) to mucin was evaluated. The strains tested exhibited different interaction patterns with the glycoconjugates, suggesting the participation of different carbohydrate-recognition sites in adhesion. Galactosylation and lactosylation of both β-Lg and SC significantly decreased the adhesion values of E. coli CBL2 to mucin. Whereas the adhesion of E. coli CBM1 was preferably interfered by galactosylated glycoconjugates obtained under the harshest incubation conditions, the adhesion capacity of E. coli CBL8 was not affected. Competitive adhesion assays with lectins, which recognise different epitopes, supported the idea that galactose-reactive adhesins are partly responsible for the recognition of these glycoconjugates. The analysis of the presence of gene coding for several virulence factors in the E. coli strains by PCR revealed the absence of K88 gene in the CBL2 strain assayed. These findings suggest that the formation of Maillard-type neoglycoproteins under controlled conditions may be a simple and cost-effective method for producing new food ingredients with the potential ability to block pathogen adhesins involved in mucosal colonisation.     

Maillard glycation of β‐lactoglobulin induces conformation changes

Glycation by the Maillard reaction is an ubiquitous reaction of condensation of a reducing sugar with amino groups of proteins, which products could improve the functional and/or biological properties for food and non‐food uses. It can induce structural modifications in proteins, modifying their properties. The aim of this work was to investigate the association behavior and the conformational changes of β‐lactoglobulin (BLG) after its glycation by the Maillard reaction with several alimentary sugars (arabinose, galactose, glucose, lactose, rhamnose and ribose). Protein samples were heated in the presence or in the absence (heated control) of different sugars during 3 days at 60°C. Glycation induced oligomerization of BLG monomers. Depending on the reactivity of the sugar, the population of produced oligomers showed smaller or greater heterogeneity in molecular masses. Analysis of modified BLG by circular dichroism and by its susceptibility to pepsinolysis showed that the conditions of heating used did not significantly alter the conformation of BLG. Heating of BLG in presence of sugars induced only minor structural modification, when using the less reactive sugars such as lactose and rhamnose. It was, however, at the origin of major three‐dimensional destructuring in the case of the more reactive sugars such as arabinose and ribose. Pepsinolysis of glycated BLG did not affect about 62 and 35% of the protein molecules modified with lactose or rhamnose, and arabinose or ribose, respectively. The increase of susceptibility of glycated BLG to pepsinolysis could be related to the alteration of the conformation of the protein when glycation was performed with highly reactive sugars, as observed by circular dichroism and calorimetry analysis.     

Effects of Sodium Caseinate on the Rheological Properties of Starch Pastes

Effects of sodium caseinate on the rheological properties of starch-water pastes have been measured under steady shear conditions. In all cases a power law equation was found to describe the variation of viscosity with shear rate. The sodium caseinate increased the viscosity of the starch pastes and a starch-sodium caseinate synergistic effect occurred. Sodium caseinate caused the swollen starch particles in pastes to increase in volume. It is suggested that this is one of the factors responsible for the observed effects of sodium caseinate on rheological behavior.     

Elucidation of mechanism of aminoreductone formation in the Maillard reaction of lactose

The aim of this study was to elucidate the formation mechanism of aminoreductone, an important indicator for estimating the extent of Maillard reaction of lactose and amino compounds. Using the model system of lactose and butylamine, the model solution of lactose and milk proteins, and milks, it was concluded that d ‐galactose was liberated at the same time as the generation of aminoreductone. It was shown that the extent of the Maillard reaction and the lactose degradation during heating depended closely on the concentration ratio of amino group/lactose in the sample solution.     

Glycation of caseinate by fructose and fructo‐oligosaccharides during controlled heat treatment in the ‘dry’ state

This paper investigates the controlled heating of caseinate with reducing sugars to produce glycoproteins with improved functionality for use in food. Caseinate was combined with inulin, fructose and a mixture of both inulin and fructose and the lyophilisates heated at a controlled water activity for up to 48 h. Caseinate–glucose and caseinate–lactose glycoconjugates were prepared for comparison. Conjugation between caseinate and fructose occurred readily at 60 °C and 67% relative humidity, modifying up to 75% of the lysine groups of caseinate within 48 h. Moreover, when reconstituted, the caseinate–fructose glycoconjugates showed a dramatic increase in viscosity relative to caseinate ‘dry’‐heated alone. At 80% relative humidity the reaction proceeded so rapidly that gels containing darkly coloured particulate matter were formed. Incorporation of inulin prevented formation of caseinate–fructose gels, and minimised browning development while still producing moderately viscous solutions. Based on ¹³C‐NMR, SDS‐PAGE and electron microscopy techniques, mechanisms by which inulin modified the reaction have been proposed. Copyright © 2005 Society of Chemical Industry     

Maillard glycation of beta-lactoglobulin induces conformation changes

Glycation by the Maillard reaction is an ubiquitous reaction of condensation of a reducing sugar with amino groups of proteins, which products could improve the functional and/or biological properties for food and non-food uses. It can induce structural modifications in proteins, modifying their properties. The aim of this work was to investigate the association behavior and the conformational changes of beta-lactoglobulin (BLG) after its glycation by the Maillard reaction with several alimentary sugars (arabinose, galactose, glucose, lactose, rhamnose and ribose). Protein samples were heated in the presence or in the absence (heated control) of different sugars during 3 days at 60 degrees C. Glycation induced oligomerization of BLG monomers. Depending on the reactivity of the sugar, the population of produced oligomers showed smaller or greater heterogeneity in molecular masses. Analysis of modified BLG by circular dichroism and by its susceptibility to pepsinolysis showed that the conditions of heating used did not significantly alter the conformation of BLG. Heating of BLG in presence of sugars induced only minor structural modification, when using the less reactive sugars such as lactose and rhamnose. It was, however, at the origin of major three-dimensional destructuring in the case of the more reactive sugars such as arabinose and ribose. Pepsinolysis of glycated BLG did not affect about 62 and 35% of the protein molecules modified with lactose or rhamnose, and arabinose or ribose, respectively. The increase of susceptibility of glycated BLG to pepsinolysis could be related to the alteration of the conformation of the protein when glycation was performed with highly reactive sugars, as observed by circular dichroism and calorimetry analysis.     

Maillard Reaction Products as Encapsulants for Fish Oil Powders

The use of Maillard reaction products for encapsulation of fish oil was investigated. Fish oil was emulsified with heated aqueous mixtures comprising a protein source (Na caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrates (glucose, dried glucose syrup, oligosaccharide) and spray‐dried for the production of 50% oil powders. The extent of the Maillard reaction was monitored using L*, a*, b* values and absorbance at 465 nm. Encapsulation efficiency was gauged by measurement of solvent‐extractable fat and the oxidative stability of the fish oil powder, which was determined by assessment of headspace propanal after storage of powders at 35 °C for 4 wk. Increasing the heat treatment (60 °C to 100 °C for 30 to 90 min) of sodium caseinate‐glucose‐glucose syrup mixtures increased Maillard browning but did not change their encapsulation efficiency. The encapsulation efficiency of all heated sodium caseinate‐glucose‐glucose syrup mixtures was high, as indicated by the low solvent‐extractable fat in powder (<2% powder, w/w). However, increasing the severity of the heat treatment of the sodium caseinate‐glucose‐glucose syrup mixtures reduced the susceptibility of the fish oil powder to oxidation. The increased protection afforded to fish oil in powders by increasing the temperature‐time treatment of protein‐carbohydrate mixtures before emulsification and drying was observed irrespective of the protein (sodium caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrate (glucose, glucose/dried glucose syrup, or oligosaccharide/dried glucose syrup) sources used in the formulation. Maillard reaction products produced by heat treatment of aqueous protein‐carbohydrate mixtures were effective for protecting microencapsulated fish oil and other oils (evening primrose oil, milk fat) from oxidation.     

葡聚糖接枝对大豆蛋白功能特性及结构的影响

采用干热糖基化对大豆分离蛋白进行改性,研究其功能特质及结构特性。以葡聚糖和大豆分离蛋白(soy protein isolate,SPI)为原料,考察底物质量比和反应时间两个因素。结果表明:蛋白质与糖质量比2∶1,反应温度60℃时,产物接枝比较高,褐变程度中等;与SPI相比,糖基化之后大豆蛋白的溶解度提高了72.72%,乳化活性(emulsifying activity,EAI)和乳化稳定性(emulsion stability,ESI)分别提高了117.53%和134.20%。十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)表明SPI与葡聚糖发生了糖基化反应;傅里叶红外光谱(Fourier transform infrared spectroscopy,FT-IR)和荧光光谱分析表明,糖链的引入导致了大豆蛋白空间结构的变化;模拟体外消化特性结果表明,葡聚糖糖基化修饰对SPI体外消化性的改善效果不明显。     

Effect of phosphatase/transglutaminase treatment on molar mass distribution and techno-functional properties of sodium caseinate

Sodium caseinate was enzymatically dephosphorylated by alkaline or acid phosphatase prior to incubation with microbial transglutaminase. It was demonstrated that a higher degree of protein cross-linking by transglutaminase was achieved in dephosphorylated sodium caseinate than in non-dephosphorylated sodium caseinate. During transglutaminase treatment, about 70% protein polymers >200.000 g/mol were produced from untreated sodium caseinate, but about 90% protein polymers >200.000 g/mol from dephosphorylated sodium caseinate. Phosphatase/transglutaminase-treated sodium caseinate exhibited techno-functional properties similar to transglutaminase-treated sodium caseinate, but performed improved interfacial stabilisation behaviour as well as higher viscosity.     

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.     

Effect of glycation on sodium caseinate-stabilized emulsions obtained by ultrasound

This work explores the potential of high-intensity ultrasound to produce fine-dispersion, long-time-stable, oil-in-water emulsions prepared with native and glycated bovine sodium caseinate (SC). Regardless the ultrasound amplitude and time assayed, the sonicated emulsions of native SC at 0.5 mg/mL had much higher emulsifying activity indexes compared with those emulsions formed by Ultra-Turrax (IKA Werke GmbH & Co., Staufen, Germany) homogenization. Nevertheless, the native SC emulsions were very unstable despite the optimization of parameters such as protein concentration, amplitude of ultrasound wave, and sonication time by using a Box-Behnken design. Early glycation of SC with either galactose, lactose, or 10 kDa dextran substantially improved both emulsifying activity and the stability, whereas at advanced stages of glycation, SC emulsions showed notably reduced emulsifying properties, likely because extensive glycation of SC promoted its polymerization mainly through covalent cross-linking, as was demonstrated by particle size measurements. The increase in particle diameter of glycoconjugates likely affected the diffusion of SC from bulk to the oil-water interface and slowed the reorientation process of the protein at the interface. These findings show that the combined effect of early-stage glycation of SC and high-intensity ultrasound as an emergent technique to form emulsions has the potential to provide improved emulsions that could be used in several food applications.     

Prior lactose glycation of caseinate via the Maillard reaction affects in vitro activities of the pepsin-trypsin digest toward intestinal epithelial cells

The well-known Maillard reaction in milk occurs between lactose and milk proteins during thermal treatment, and its effects on milk nutrition and safety have been well studied. A lactose-glycated caseinate was prepared via this reaction and digested using 2 digestive proteases, pepsin and trypsin. The glycated caseinate digest was assessed for its in vitro activities on rat intestinal epithelial cells in terms of growth proliferation, anti-apoptotic effect, and differentiation induction using caseinate digest as reference, to verify potential effects of the Maillard reaction on these activities of caseinate digest to the cells. Two digests had proliferative and anti-apoptotic effects, and reached the highest effects at 0.02 g/L of digest concentration with treatment time of 24 h. In comparison with caseinate digest, glycated caseinate digest always showed weaker proliferative (5.3–14.2%) and anti-apoptotic (5.9–39.0%) effects, and was more toxic to the cells at 0.5 g/L of digest concentration with treatment time of 48 h. However, glycated caseinate digest at 2 incubation times of 4 to 7 d showed differentiation induction higher than caseinate digest, as it could confer the cells with increased activities in lactase (16.3–26.6%), sucrase (22.4–31.2%), and alkaline phosphatase (17.4–24.8%). Transmission electron microscopy observation results also confirmed higher differentiation induction of glycated caseinate digest. Amino acid loss and lactose glycation partially contributed to these decreased and enhanced activities of glycated caseinate digest, respectively. The Maillard reaction of caseinate and lactose is thus shown in this study to have effects on the activities of caseinate digest to intestinal epithelial cells.     

Simultaneous analysis of Nε-(carboxymethyl)lysine,reducing sugars,and lysine during the dairy thermal process

A new analytical method allowing the simultaneous quantification of Nε-(carboxymethyl)lysine (CML), lysine, and reducing sugars (glucose, lactose, and galactose) is described. It is based on high performance anion-exchange chromatography with pulsed amperometric electrochemical detection. This method demonstrated a low limit of quantification (0.385 to 0.866 mg/L), excellent linear correlation (R² > 0.997), and desired calibration range (3.125 to 25 mg/L). In addition, lactose-lysine solutions containing sulfite (4 to 400 mmol/L) were heated at 110°C for 2 h. The results showed that sulfite inhibited the formation of CML and promoted the consumption of reducing sugars and lysine in the Maillard reaction model. The method proved to be useful for simultaneous analysis of CML, lysine, and reducing sugars (glucose, galactose, and lactose) in the Maillard reaction system. Moreover, sulfite was an effective inhibitor of CML formation.     

Effect of the Reactant Ratio on the Characteristics and Antioxidant Activities of Maillard Reaction Products in a Porcine Plasma Protein Hydrolysate-Galactose Model System

The chemical characteristics and antioxidant properties of Maillard reaction products formed in the Maillard reaction in a model system at 95°C for different lengths of time (0–6 h) were investigated at three mass ratios (1:1, 1:2, and 1:3) of porcine plasma protein hydrolysate to galactose. The results revealed that the pH value and free amino group content decreased (p < 0.05), whereas the browning index, intermediate products, and browning intensity, as well as reducing power and 2,2’-amino-di(2-ethyl-benzothiazoline sulfonic acid-6)ammonium salt radical scavenging activity of the Maillard reaction products increased as the reaction time increased (p < 0.05). Moreover, when the mass ratio of porcine plasma protein hydrolysate to galactose was 1:3, the Maillard reaction progressed easily, which rendered a higher degree of glycation and antioxidant activity (p < 0.05). These results indicated that the Maillard reaction can improve the antioxidant capacity of porcine plasma protein hydrolysate.     

Physicochemical properties of pectins from okra (Abelmoschus esculentus (L.) Moench)

Okra pectin obtained by hot buffer extraction (HBSS) consists of an unusual pectic rhamnogalacturonan I structure in which acetyl groups and alpha galactose residues are substituted on rhamnose residues within the backbone. The okra Chelating agent Soluble Solids (CHSS) pectin consists of slightly different structures since relatively more homogalacturonan is present within the macromolecule and the rhamnogalacturonan I segments carry slightly longer side chains. The rheological properties of both okra pectins were examined under various conditions in order to understand the unusual slimy behaviour of okra pectins. The viscosity of the okra HBSS pectin was 5–8 times higher than the viscosity of the okra CHSS pectin. The okra HBSS pectin showed an elastic behaviour (G′ > G″) over a wide range of frequencies (10⁻¹–10 Hz), at a strain of 10%, while okra CHSS and saponified okra HBSS/CHSS pectin showed predominantly viscous responses (G′ < G″) over the same frequency range. The results suggest that the structural variation within the okra pectins greatly affect their rheological behaviour and it is suggested that acetylation of the pectin plays an important role through hydrophobic associations. Dynamic light scattering was used to study the association behaviour of both okra pectins at low concentration (0.001–0.1% w/w). Results showed that the saponified okra pectins did not exhibit a tendency to aggregate in the concentration range studied, whereas both non saponified samples showed a substantial degree of association. These results suggest that the unusual slimy behaviour of the non saponified samples may be related to the tendency of these pectins to associate, driven by hydrophobic interactions.     

盐及酪蛋白酸钠对藜麦面团及面条品质的影响

本文以藜麦面为研究对象,通过添加KCl、NaCl、酪蛋白酸钠以改善藜麦面团的性质,研究了不同处理条件对藜面团质的硬度、咀嚼性、黏度等质构特性以及储能模量、损耗模量、复合粘度等流变学特性的影响。结果表明:当添加的水量为50%藜麦面团成型的光滑程度、弹性较好;当藜麦面中加入1.5%酪蛋白酸钠+1% KCl所制备的藜麦面团粘性适中、硬度和弹性较好;NaCl、KCl、酪蛋白酸钠的加入,均可改善面团的G'、G'、黏度,1.5%酪蛋白酸钠+1% KCl加入,可增大藜麦面团的G'、G'、黏度;NaCl和酪蛋白酸钠都可以明显的改善藜麦面条吸水率,NaCl可降低藜麦面条的干物质损失率,KCl的作用与之相反,而酪蛋白酸钠与1% KCl联合使用,在增加其吸水率的同时减少了干物质损耗率,当同时添加2.0%酪蛋白酸钠和1% KCl条件下达到最适,而且恢复能力达到最佳;酪蛋白酸钠与1% KCl可增加藜麦面条表面片层的致密程度。因此,1.5%酪蛋白酸钠+1% KCl的添加量对藜麦面团的弹性、硬度、咀嚼性均达到最佳,同时添加2.0%酪蛋白酸钠和1% KCl能显著（P<0.05）改善藜麦面条的蒸煮损失及干物质损失率,降低面汤浊度,还可以增加藜麦面条的硬度,从而增加其咀嚼性。