Maillard Reaction Model Research Articles

Study on the Hydroxyl Radical Scavenging Activity Changes of Ginseng and Ginsenoside-Rb2 by Heat Processing

The free radical scavenging activities of Panax ginseng C.A. MEYER are known to increase by heat processing. Phenolic acids and Maillard reaction products (MRPs) have been suggested as active free radical scavenging components from our previous research, but heat processing-induced chemical and activity changes of ginsenosides considering the Maillard reaction have not yet been fully elucidated. In this study, we investigated the hydroxyl radical (.OH) scavenging activity changes of ginsengs and ginsenoside-Rb2 (Rb2)) by heat processing using an electron spin resonance spectrometer. Especially, Rb2 was heat processed with the same amount of glycine, a frequently used amino acid in the Maillard reaction model system. As a result, the .OH scavenging activities and brown compound levels of ginseng and glycine-Rb2 mixture were increased by heat processing. However, the increase in .OH scavenging activities were not in accordance with the extents of browning. On the other hand, less-polar ginsenosides such as Rg3, Rg5, and Rk1 were generated from the glycine-Rb2 mixture by heat processing. The sugar moieties at carbon-20 of Rb2 were separated by the steaming process, less-polar ginsenosides were produced, and then the separated sugar moieties were thought to form MRPs with glycine. From the .OH scavenging activity tests of Rb2, glycine, less-polar ginsenosides, and maltol, the increase in .OH scavenging activity was thought to be more closely related to the generation of .OH scavenging ginsenosides such as 20(S)-Rg3 and Rg5 by heat processing than MRPs.

Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions: part 1

The correlations between formation of melanoidins and the content of α-dicarbonyl compounds and colour formation were studied in Maillard reaction model sucrose solutions at high treating temperatures (130 °C) corresponding to the industrial sucrose processing. Molecular weight distribution was determined by gel permeation chromatography (GPC) and α-dicarbonyls as high reactive intermediates of the Maillard reaction were detected by RP-HPLC and GC/MS. Referring to formation of melanoidins, new knowledge could be gained. The investigations clearly point out, that individual α-dicarbonyls are involved in formation of specific molecular weight fractions. 3-Deoxyhexosulose (3-DH) and methylglyoxal are the important α-dicarbonyl compounds in thermal-treated sucrose solutions. A low molecular weight fraction with a molecular weight range of <5,800 g/mol preferably occurs when 3-DH is formed in high concentrations. The high increase in intensity of a low molecular weight fraction is combined with a strong colour formation. In contrast to 3-DH, methylglyoxal promotes the formation of high molecular weight fractions between 6,600 g/mol and approximately 17,000 g/mol. Furthermore, model solutions with a high intensity of high molecular weight fractions show an early colour formation during the starting period of the reaction. Indeed, this early browning is not as intensive as the colour formation caused by the low molecular weight fraction during the later stage of the browning reaction. Out of this, 3-DH can be regarded as the most important intermediate for an intensive colour formation in sucrose solutions.

Determination of Acrylamide Formed in Asparagine/d-Glucose Maillard Model Systems by Using Gas Chromatography with Headspace Solid-Phase Microextraction

A gas chromatographic method, along with a headspace solid-phase microextraction (HS-SPME), was developed for the determination of acrylamide formed in Maillard reaction model systems. The developed method was validated by liquid chromatography/mass spectrometry. A headspace sample was collected from an aqueous acrylamide solution (100 microg/mL) by SPME and directly injected into a gas chromatograph equipped with a nitrogen-phosphorus detector. The recovery of acrylamide from an aqueous solution was satisfactory, i.e, >93% under the conditions used. Acrylamide formed in an asparagine/D-glucose (molar ratio, 1/2) Maillard reaction model system heated at 150 and 170 degrees C for 20 min was collected and analyzed by the newly developed method using gas chromatography with nitrogen-phosphorus detection and HS-SPME. The amounts of acrylamide were 318 +/- 33 microg/g asparagine from a sample heated at 150 degrees C and 3329 +/- 176 microg/g asparagine from a sample heated at 170 degrees C. Addition of cysteamine or glutathione to the above model system reduced acrylamide formation. Acrylamide formation was not observed when cysteamine or glutathione was added to asparagine in the above model systems to obtain equimolar concentrations of both compounds. This newly developed method is simple and sensitive, and requires no solvent extraction.

Assessing the non-specific hydroxyl radical scavenging properties of melanoidins in a Fenton-type reaction system

Soluble high molecular weight fraction (>10 kDa, named melanoidins) was isolated from Maillard reaction model systems, coffee, beer and sweet wine by ultrafiltration. Deoxyribose method was adjusted for measuring the hydroxyl radical scavenging properties of melanoidins. The presence of competitive melanoidins with deoxyribose for OH decrease the rate of deoxyribose degradation. Possible interferences to the deoxyribose method have been evaluated. Most of isolated melanoidins exhibited a variable and measurable non-site-specific hydroxyl scavenging activity in a Fenton-type reaction system. The iron reducing properties of melanoidins at the reaction conditions were evaluated with ferrozine. It has established a kinetic approach to assess the second rate constants of hydroxyl radical scavenging reactions of melanoidins. This approach may be a valuable tool for addressing the structure–activity relationships of melanoidins in a future. There is no correlation between browning (absorbance at 420 nm) and efficiency for scavenging hydroxyl radicals in solution.

Antioxidant activity of sugar–lysine Maillard reaction products in cell free and cell culture systems

Model Maillard reaction (MR) products (MRPs) employing lysine with an aldohexose (e.g., glucose), ketohexose (e.g., fructose), and aldopentose (e.g., ribose) sugars were generated (e.g., pH 9.0; over 2 h heating at 120°) and fractionated with ethanol into low (LMW) and high (HMW) molecular weight fractions. Characteristically different temporal patterns of fluorescence and ultraviolet/visible absorption spectra were obtained from the three distinct sugar–lysine MRPs, and corresponded to different yields of total and dialyzable carbon, indicating that relative reaction rates and degree of polymerization favored the Rib–Lys MRP, compared to Glu–Lys and Fru–Lys MRPs, respectively ( p < 0.05). Further characterization of antioxidant activity of the sugar specific-lysine MRPs in chemical (e.g., hydrophobic (1,1,-diphenyl-2-picryl-hydrazyl radical (DPPH) and hydrophilic (Fenton reaction-induced hydroxyl radical) in vitro scavenging assays showed that Rib–Lys HMW MRPs had the highest ( p < 0.05) affinity to scavenge free radicals. All sugar–Lys MRPs, however, displayed similar protection of cultured Caco-2 cells from exposure to H 2O 2-, 2,2′-azobis-(2-amidinopropane) dihydrochloride (AAPH)-, ferrous (Fe 2+)-, and cupric (Cu 2+)-induced cytotoxicity, evaluated both from redox (e.g., MTT response) and cell membrane integrity (e.g., LDH secretion). HMW-MRPs exhibited stronger ( p < 0.05) antioxidant activity to scavenge hydroxyl and DPPH radicals, and a greater ( p < 0.05) protective effect against both Fe 2+- and Cu 2+-induced cytotoxicity in Caco-2 cells than corresponding LMW-MRPs. We conclude that HMW MRPs possess affective antioxidant protection against oxidizable substrates; however, the degree of polymerization of this product, characteristic to the source of monosaccharide used in the reaction, is not a distinguishable factor for this bioactivity.

The effect of sugar, amino acid, metal ion, and NaCl on model Maillard reaction under pH control.

The color intensities was determined of Maillard reaction products (MRPs) prepared by heating each of five sugars (maltose, fructose, glucose, arabinose, and xylose) with each of 12 amino acids (aspartic acid, glutamic acid, alanine, leucine, isoleucine, valine, proline, serine, cysteine, phenylalanine, arginine, and lysine). The remaining percentages of glucose and rate of change of color intensity due to the addition of a metal ion and NaCl were monitored for nine MRPs that had been formed between glucose and each of nine amino acids (aspartic acid, glutamic acid, alanine, valine, serine, cysteine, phenylalanine, arginine, and lysine). Model MRPs were prepared in a block heater at 100 degrees C for 1-12 h with the pH value controlled at 6.5. The resulting color intensity of each MRPs formed from the basic amino acids was greater due to the higher reactivity than those from the acidic amino acids. The remaining percentage of glucose in each MRPs from the basic amino acids was lower than those from the acidic amino acids. The MRPs from the nonpolar amino acids showed an intermediate color intensity and remaining percentages of glucose between those formed from the basic and acidic amino acids. Browning tended to be accelerated in the presence of metal ions, especially Fe2+ and Cu2+, although it was affected by the property of the amino acid and heating time as well as by the type of metal ion. On the other hand, browning was greatly inhibited by a high concentration of NaCl.

Determination of Reductones, Furans and Organic Acids in Aqueous Model Matrices Using Solid-Phase Extraction and Gas Chromatography/Mass Spectrometry

A method using solid-phase extraction (SPE) and GC-MS was developed for the determination of a series of polar and unstable flavor compounds: reductones, furans and volatile organic acids, in aqueous model matrices. The SPE procedures were optimized mainly on the pH-dependency of the analytes with regard to their adsorption characteristics. Good recovery of the reductones except DDMP was obtained at pH 2 and 4.5. Furan derivatives were generally recovered in high yields under the acidic to neutral pH conditions examined. All organic acids were recovered almost quantitatively at pH 2. An essentially comparable result was obtained in a model Maillard reaction mixture. In order to apply this method to alcoholic beverages, effect of the ethanol concentration on the SPE adsorption of the analytes was also investigated.

Simultaneous quantitative analysis of maillard reaction precursors and products by high-performance anion exchange chromatography.

A new analytical setup allowing the simultaneous analysis of precursors and products of the Maillard reaction is described. It is based on high-performance anion exchange chromatography with electrochemical (ECD) and diode array detectors (DAD) coupled in series. Chromatography and detection were optimized to permit simultaneous monitoring of compounds relevant to the Maillard reaction, such as the sugar, the amino acid, and the corresponding Amadori compound as well as the cyclic intermediates 5-(hydroxymethyl)-2-furaldehyde, maltol, and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one. Separation was achieved on a CarboPac PA-1 column using a gradient of sodium acetate in aqueous sodium hydroxide. The Amadori compound, glucose, and glycine were monitored by an ECD operating in the integrated amperometry mode. The number of analyzed compounds was further increased by coupling the ECD with a DAD for the analysis of ultraviolet-active constituents. This method was successfully applied to model Maillard reaction mixtures based on glucose and glycine.

Formation of vinylogous compounds in model Maillard reaction systems.

The thermal degradation over temperature and time of selected amino acids (Asp, Gln, and Glu) in the presence of reducing sugars was investigated in low moisture model systems. Copyrolysis of glucose-Asp mixtures led to the release of acrylic acid, attaining >5 mmol/mol Asp at 230 degrees C after 5 min. Spurious amounts of 3-butenamide were detected upon heating Gln together with a carbonyl source. Apparently, intramolecular cyclization is favored to procure 2-pyrrolidinone, reaching levels >3 mmol/mol above 230 degrees C. 2-Pyrrolidinone was also formed in comparable amounts in pyrolyzed sugar-Glu mixtures, indicating that the Maillard reaction may be an important contributor to the formation of 2-pyrrolidinone in certain cooked foods. The chemical route to acrylic acid and 3-butenamide is probably analogous to that described for acrylamide recently. Evidence is also presented that acrylic acid may be an intermediate in the formation of acrylamide, and yields could be augmented by coincubation of fructose-Asp with certain amino acids such as Gln, reaching approximately 5% of the yield obtained by the Asn route. A computational study to determine the reactivity of the vinylogous products indicated a reduced ability of 3-butenamide as compared to acrylamide to form stable intermediates by Michael nucleophilic addition. Acrylamide and acrylic acid exhibited a similar theoretical reactivity potential toward nucleophiles. No information is as yet available on the occurrence of acrylic acid in cooked foods. Extensive toxicological evaluation indicates that acrylic acid is of no concern at the amounts to be expected in foods.

Potential of gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) in flavor research.

Gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) is an emerging technique offering a straightforward access to a resolving power up to 7000. This paper deals with the use of GC-oaTOFMS to identify the flavor components of a complex seafood flavor extract and to quantify furanones formed in model Maillard reactions. A seafood extract was selected as a representative example for complex food flavors and was previously analyzed using GC-quadrupole MS, leaving several molecules unidentified. GC-oaTOFMS analysis was focused on these unknowns to evaluate its potential in flavor research, particularly for determining exact masses. N-Methyldithiodimethylamine, 6-methyl-5-hepten-2-one, and tetrahydro-2,4-dimethyl-4H-pyrrolo[2,1-d]-1,3,5-dithiazine were successfully identified on the basis of the precise mass determination of their molecular ions and their major fragments. A second set of experiments was performed to test the capabilities of the GC-oaTOFMS for quantification. Calibration curves were found to be linear over a dynamic range of 10(3) for the quantification of furanones. The quantitative data obtained using GC-oaTOFMS confirmed earlier results that the formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone was favored in the xylose/glycine model reaction and 2(or 5)-ethyl-4-hydroxy-5(or 2)-methyl-3(2H)-furanone in the xylose/alanine model reaction. It was concluded that GC-oaTOFMS may become a powerful analytical tool for the flavor chemist for both identification and quantification purposes, the latter in particular when combined with stable isotope dilution assay.

Sucrose ester microemulsions as microreactors for model Maillard reaction

Thermal reactions of cysteine/furfural mixture were studied as a model system to gain more insight into the influence of structured fluids such as water-in-oil nonionic microemulsions on the generation of aroma compounds. The microemulsion systems were composed of: sucrose ester/water/dodecane+alcohol(1/1), where the sucrose esters are sucrose stearate (S1570) and sucrose laurate (L1695), and the alcohols are medium-chain alcohols (C 2OH to C 6OH). Formation of predominately 2-furfurylthiol (FFT) is obtained in the aqueous cysteine/furfural system. The formation of FFT was enhanced under similar reaction conditions in water-in-oil microemulsions and led to the formation of two new sulfur compounds that were identified as 2-(2-furyl)-thiazolidine and tentatively N-(2-mercaptovinyl)-2-(2-furanyl)-thiazolidine. The reaction rates (furfural conversion or consumption) decrease with the decrease in the water content and the increase in alcohol chain length (C 2 to C 6 were used as cosurfactant) and with the increase of pH from 4 to 8 in the system containing butanol as the alcohol. The rates of reaction increase also with the increase of temperature in the range of temperatures studied from 30 to 60 °C. The kinetic constants ( k) and energy of activation ( E a) were calculated. Microemulsions of W/O are excellent reaction media for the Maillard reaction providing a high selectivity, high conversion rates and specificity.

Racemization of amino acids during classical and microwave oven hydrolysis — application to aspartame and a Maillard reaction system

Abstract The conventional acid hydrolysis routinely used in protein analysis induces partial racemization of the amino acids. An alternative method, using microwave heating, was evaluated with the aim of assessing its efficiency in preserving the amino acids in their original configuration. The method was employed on the dipeptide aspartame. The results showed that some advantages, implying less racemization, could be gained by using the microwave technique, but the method was applicable only at temperatures under 150°C. Mild, conventional hot oven-hydrolysis, involving a shorter hydrolysis time, could have the same mild effect. The different techniques were applied to aspartame treated at different pH, a soft drink and a Maillard reaction model system. The results showed that aspartame was insusceptible to racemization in acid and neutral environments, and not until very high pH did racemization start. The soft drink contained a small amount of d -amino acids, 0.27 mg d -asp and 0.14 mg d -phe/100 ml. The model system exhibited no racemization.

Comparison of the antioxidative and cytotoxic properties of glucose-lysine and fructose-lysine Maillard reaction products

The antioxidative activity and cytotoxic effect of different fractions generated from whole mixtures of model Maillard reaction products (MRPs) made from glucose-lysine (Glc-Lys) and fructose-lysine (Fru-Lys) reactants were tested. MRPs were derived from Glc-Lys and Fru-Lys by autoclave heating, and ethanol fractionation. All MRP fractions showed various degrees of antioxidative activity when evaluated by a deoxyribose oxidative degradation assay. A significant difference ( P<0.05) was seen in the affinity to inhibit Fenton-reaction-induced free radical production, for both Glc-Lys and Fru-Lys ethanol precipitates, and also the Fru-Lys ethanol extract. Similar protective antioxidative activity of the different MRP fractions was not exhibited in a DNA nicking assay. Cytotoxicity potential of the MRPs was investigated using Caco-2 cells. The greater cytotoxicity observed for both Glc-Lys and Fru-Lys ethanol precipitates was specific to the higher molecular weight fractions. Cytotoxicity also depended on incubation time, MRP concentration, and sugar source.

Hydroxyl Scavenging Activity of Glucose, Fructose, and Ribose‐Lysine Model Maillard Products

ABSTRACTNondialyzable model Maillard reaction products (MRPs) were synthesized by reacting L‐lysine with D‐glucose, D‐fructose, and D‐ribose under different conditions of reaction time, temperature, pH, and water activity (aw). Five experiments common to all three models yielding greater than 0.5g of MRPs were assessed for antioxidant activity. All MRPs exhibited detectable, but variable, non site‐specific hydroxyl radical (·OH) scavenging activity (30–90%) in the deoxyribose assay. MRPs derived from a ribose‐lysine study showed the highest ·OH scavenging activity (80–90%) in both deoxyribose and DNA nicking assays. All MRPs at higher concentrations (0.2 mg/mL) decreased lipid peroxidation in linoleic acid emulsions. Relative effectiveness of different MRPs to scavenge free radicals can vary with reaction conditions and substrates.

The effect of high pressure on the formation of volatile products in a model Maillard reaction

Reaction progress in the formation and subsequent decay of several of the volatile products from a model Maillard reaction between lysine and xylose has been followed at pH 7 and 10 and at elevated pressures. At low pH, the buildup and decay of 5-methyl-4-hydroxy-3(2H)-furanone and several minor products were observed. The application of high pressure results in a much diminished maximum concentration of each although the time to the maximum is unaffected. At pH 10, products contain nitrogen heterocycles with 2-methylpyrazine being the principal one which builds up and only slowly decays with time. Again, the yield is greatly reduced by pressure. The results are interpreted in terms of the inhibition by pressure of the formation of the precursor, the Amadori rearrangement product which affects subsequent products. In some instances rates of formation are also found to be slightly inhibited while degradation of these products is accelerated. The corresponding mechanisms are examined in the light of these results.

Determination of Volatile Organic Selenium Compounds from the Maillard Reaction in a Selenomethionine−Glucose Model System

In the past, biomedicine, toxicology, and other related disciplines have made some progress with regard to the detrimental and beneficial effects of selenium in biological systems. Therefore, it is of interest to determine the chemical structure and occurrence of organoselenium compounds generated in food systems via the Maillard reaction. The Maillard reaction involves the reaction of amino acids with reducing sugars and occurs in many food systems during processing under high-temperature conditions and is responsible for the generation of many volatiles. This research describes a model Maillard reaction system between the amino acid selenomethionine and a reducing sugar, glucose, to generate volatile organoselenium compounds. Using gas chromatography and gas chromatography−mass spectrometry, five selenium compounds were tentatively identified and semiquantitative values for concentration obtained. Keywords: Organoselenium; selenomethionine; Maillard reaction; gas chromatography (GC); gas chromatography/mass spectrometry (GC/MS)

Oxidative Reactions of Model Maillard Reaction Products and α‐Tocopherol in a Flour‐Lipid Mixture

ABSTRACTNondialyzable model Maillard reaction products (MRPs) were prepared by heating 0.8M D‐glucose or D‐fructose with 0.8M L‐lysine under different reaction conditions and times. The usefulness of derived MRPs, with highest melanoidin yields, in stabilizing oxidative deterioration in food was evaluated in a flour‐lipid dough mixture with or without cupric ions. Glucose‐lysine MRPs effectively reduced lipid oxidation both with and without cupric ions. In contrast, fructose‐lysine MRPs lowered lipid oxidation only without cupric ions, and accelerated lipid oxidation with cupric ions. Application of MRPs in combination with α‐tocopherol showed no synergistic or antagonistic effect. Conditions and type of reducing sugar in synthesis of MRPs can influence their anti‐ or pro‐oxidant activity.

Volatile Compounds Generated in Serine−Monosaccharide Model Systems

The model Maillard reactions of serine−ribose (S−R) and serine−glucose (S−G) were studied. The reactions were conducted in a pH 8 aqueous solution at 160 °C for 2 h. Three times more volatiles were generated in the S−R system than in the S−G system, and in total, 37 compounds were identified in the two reaction systems. Some novel pyrazines were formed in both reaction solutions. In the serine−ribose system, the identified pyrazines were 2-(2-furfuryl)pyrazine, 2-(2-furfuryl)-5(and 6)-methylpyrazine, and 2-(2-furfuryl)-3,5-dimethylpyrazine. In the serine−glucose system, 2-[5-(hydroxymethyl)-2-furfuryl]-3,5-dimethylpyrazine was the only identified bicyclic pyrazine compound. To confirm the formation of these pyrazine compounds, they were prepared in a model reaction involving acetol, ammonium acetate, and corresponding aldehydes. In such model reaction systems, we also prepared 2-(2-thienylmethyl)-3,5(and 3,6)-dimethylpyrazine and 2-(2-pyrrylmethyl)-3,5(and 3,6)-dimethylpyrazine. Mass spectra of some compounds were reported for the first time. Keywords: Serine; glucose; ribose; Maillard; volatile; flavor; roasty; pyrazine; furfuryl; acetol; aldehyde

Influence of Reaction Conditions on the Oxidative Behavior of Model Maillard Reaction Products

Model nondialyzable Maillard reaction products (MRPs) were synthesized by reacting d-glucose or d-fructose with l-lysine under four different initial reaction parameters (pH, water activity, reaction time, and temperature) and evaluated for potential antioxidant or prooxidant activity and genotoxic properties. All model Glu−Lys and Fru−Lys MRPs showed various degrees of antioxidant activity when evaluated in a metal-free model linoleic acid emulsion system using thiobarbituric acid (TBA) as an end point measure of lipid oxidation. The oxidative behavior of the same MRPs, when determined by an oxygen electrode in the presence of copper ions, consisted of both prooxidant and antioxidant activities for specific MRPs. Using an in vitro DNA model system, both Glu−Lys and Fru−Lys MRP mixtures induced significant (p ≤ 0.05) strand breakage in PM2 bacteriophage DNA at high concentrations (>0.001%, w/v). In general, Fru−Lys MRPs exhibited more prooxidant and genotoxic activity compared to Glu−Lys MRPs synthesized ...

Antioxidative Effect of Maillard Reaction Products Using Glucose−Glycine Model System

Using a glucose−glycine system as a Maillard reaction model, the rate of inhibition toward active oxygen by Maillard reaction products (MRP) was investigated by electron spin resonance (ESR). MRP o...