Glucose Model System Research Articles

Effects of certain polyphenols and extracts on furans and acrylamide formation in model system, and total furans during storage

Using a glucose–glycine and asparagine–fructose system as a Maillard reaction model, the effects of seven polyphenols and solid phase extracts of three plants on the formation of furans and acrylamide were investigated. The polyphenols and extracts were used in biscuit formulation and acrylamide formation was observed. They were used for the storage of the glycine–glucose model system at three different temperatures. The addition of some of the extracts and polyphenols significantly decreased furan formation to different extents. All phenolic compounds and plant extracts decreased in the range of 30.8–85% in the model system except for oleuropein, and all of them decreased in the range of 10.3–19.2% in biscuit. Total furan formation was inhibited by caffeic acid, punicalagin, epicatechin, ECE and PPE during storage. This study evaluated and found the inhibitory effect on the formation of furans and acrylamide in Maillard reactions by the use of some plant extracts and polyphenols.

Faox enzymes inhibited Maillard reaction development during storage both in protein glucose model system and low lactose UHT milk

Fructosamines, also known as Amadori products, are formed by the condensation of glucose with the amino group of amino acids or proteins. These compounds are precursors of advanced glycation end products (AGEs) that can be formed either endogenously during aging and diabetes, and exogenously in heat-processed food. The negative effects of dietary AGEs on human health as well as their negative impact on the quality of dairy products have been widely described, therefore specific tools able to prevent the formation of glycation products are needed. Two fructosamine oxidase enzymes isolated from Aspergillus sp. namely, Faox I and Faox II catalyze the oxidative deglycation of Amadori products representing a potential tool for inhibiting the Maillard reaction in dairy products. In this paper, the ability of recombinant Faox I and II in limiting the formation of carboxy-methyl lysine (CML) and protein-bound hydroxymethyl furfurol (b-HMF) in a commercial UHT low lactose milk and a beta-lactoglobulin (β-LG) glucose model system was investigated. Results show a consistent reduction of CML and b-HMF under all conditions. Faox effects were particularly evident on b-HMF formation in low lactose commercial milk. Peptide analysis of the β-LG glucose system identified some peptides, derived from cyanogen bromide hydrolysis, as suitable candidates to monitor Faox action in milk-based products. All in all data suggested that non-enzymatic reactions in dairy products might be strongly reduced by implementing Faox enzymes.

Impact of phloretin and phloridzin on the formation of Maillard reaction products in aqueous models composed of glucose and l-lysine or its derivatives

In the present study, the effects of phloretin and phloridzin on the formation of Maillard reaction products in a lysine-glucose model with different reactant ratios were systematically investigated. In terms of the formation of Maillard-type volatiles, phloretin and phloridzin treatmen could significantly reduce their generation, where the effects depend on the ratio of lysine to glucose used in the model systems. Phloretin and phloridzin could also affect the colour development of Maillard reactions; especially phloretin, which could significantly promote the formation of brown products in the system with the lowest ratio of lysine to glucose. Based on the carbon module labelling (CAMOLA) technique and HPLC-DAD-ESI/MS analysis, it was found that phloretin and phloridzin could actively participate in the Maillard reaction and directly react with different reactive carbonyl species. The effect of phloretin and phloridzin treatment in both N(α)-acetyllysine-glucose (AC-glu), and N-acetyl-gly-lys methyl ester acetate salt-glucose (AG-glu) model systems, which are close to the Maillard reactions occurring in real food, where the free amino groups of lysine residues were considered as the reactive site, were further investigated. Similar impacts on the formation of Maillard-type volatiles and brown products as in the lysine-glucose models were observed which can also be explained by the capability of phloretin and phloridzin to quench sugar fragments formed in these model reactions.

The Effect of High Pressure−High Temperature Processing Conditions on Acrylamide Formation and Other Maillard Reaction Compounds

The effect of high pressure-high temperature (HPHT) processing on the formation of acrylamide and other Maillard-type reaction compounds was investigated in order to elucidate the impact of HPHT conditions on the different stages of the Maillard reaction. This study was performed in equimolar asparagine-glucose model systems that were treated at various HP/HT conditions (100-115 °C, 400-700 MPa, 0-60 min), and, for comparison, the model system was also heat-treated at ambient pressure. On the treated samples, the concentration of acrylamide, reactants, hydroxymethylfurfural, organic acids, and melanoidins was determined and the pH prior to and after treatment was measured. Based on the measured responses, the retarding effect of high pressure on the overall Maillard reaction was demonstrated; no or little differences were observed between 400 and 700 MPa. The study was conducted in two types of buffer, i.e. phosphate and MES buffer. In case of acrylamide, aspartic acid and browning, a higher concentration was generated in the MES buffer system, but these differences with the phosphate buffer system could be ascribed to pH changes resulting from the application of combined high pressure and high temperature. Based on the results, acrylamide formation is not expected to pose a major hazard to HPHT-treated products.

GENERATION OF MEAT-LIKE VOLATILES FROM CYSTEINE, GLUCOSE AND SERINE MODEL SYSTEM AND ITS ANTIOXIDANT ACTIVITY

Reaction between Cysteine, Glucose and Serine was carried out to study the volatiles formed via Maillard reaction and their antioxidant activity. The simultaneous distillation–extraction technique was used for trapping the volatile components followed by GC–MS analysis. Thirty Six compounds were identified with the predominance of carbonyls and sulfur–containing compounds in the volatiles of this model system. Sensory evaluation was performed for the model system product according to the International Standard Methods (ISO). The results showed a high increase in roasted and burnt meat attributes. The sensory results of the model system product were confirmed by the presence of high concentrations of some volatile compounds having meat–like aroma such as 2-methyl-3-furanthiol and 2-furylmethanethiol attributes and remarkable increase in the like– roasted meaty aroma. The radical scavenging activity of cysteine, glucose and serine model system was quantified spectrophotometrically, using DPPH radical. The activity of the model system product was found to be slightly lower than that of gallic acid and BHA, but it was much higher than that of cinnamic acid (200 ppm. for each). A highly antioxidative activity was recorded by the model system which may be due to the presence of some compoundssuch as 2-furylmethanethiol, 2-acetylthiazole, 4-hydroxy-5-methyl-3(2H)-furanone.

A pulsed electric field procedure for promoting Maillard reaction in an asparagine–glucose model system

SummaryEffects of pulsed electric field (PEF) on pH, intermediate products, asparagine and glucose content, browning value, reducing power as well as antioxidant activity of an asparagine–glucose solution were explored in this paper. Results showed that the solution’s UV–Vis absorbance at 294 nm and 420 nm was significantly increased from 0 to approximately 1.14 and 0.74, respectively, at PEF intensity of 40 kV cm−1 for 7.35 ms treatment. The temperature of PEF treated samples were overall lower than 40 °C. It was also detected that the antioxidant activity of treated sample was correspondingly increased by 20.33%. Meanwhile, 14% reduction of asparagine content and 66% reduction of glucose content were observed. It was demonstrated from high performance liquid chromatography analysis that Maillard reaction in the model system had been enhanced by PEF treatment as no 5‐hydroxymethyl‐2‐furaldehyde was generated. This study indicates that pulsed electric field treatment, especially with higher intensities, is a means to significantly promote the Maillard reaction in an asparagine–glucose solution.

Study on the Maillard Reaction Enhanced by Pulsed Electric Field in a Glycin–Glucose Model System

Effects of pulsed electric field (PEF) on glycin and glucose content, browning value, and antioxidant activity of a glycin–glucose solution were explored. Results showed that at PEF intensity of 40 kV/cm, the solution’s absorbance at 420 nm was significantly increased from 0 to approximately 0.17 after 7.35-ms treatment. The temperature of PEF-treated samples was overall lower than 40 °C. It was also detected that the antioxidant activity of treated sample was increased to 39.36%. Moreover, 13.09% glycin and 50.76% glucose were consumed during the Maillard reaction in this experiment. This study indicates that pulsed electric field treatment, especially with higher intensity over 30 kV/cm, is a promising method to significantly promote the Maillard reaction in glycin–glucose solution.

Effects of Ultrasound on a Glycin–Glucose Model System—A Means of Promoting Maillard Reaction

Effects of ultrasound on pH, intermediate products, browning, glycin and glucose contents, reducing power, and antioxidant activity of a glycin–glucose solution were examined. Results showed that the ultrasonic treatment at the intensity of 17.83 W/cm2 for 50 min resulted in the increases of the solution’s absorbance at 294 and 420 nm and the antioxidant activity from approximately 0% to 2.40%, 1.19%, and 18.62%, respectively. At the same time, 21% reduction in glycin and 92% in glucose were observed. Gas chromatography/mass spectrum analysis showed that the ultrasonic treatment induced a Maillard reaction in the model system producing substances including 2,5-dimethyl-pyrazine, trimethyl-pyrazine, (Z)-9-octadecenamide, 1,2-benzenedicarboxylic acid, and mono (2-ethylhexyl) ester. This study indicated that ultrasound, especially at higher intensities, could potentially be employed as a means to promote the Maillard reaction in the glycin–glucose solution.

Characteristics and antioxidant activity of ultrafiltrated Maillard reaction products from a casein–glucose model system

Abstract Maillard reaction products (MRPs) were prepared from casein–glucose by refluxing for 130 min at 102 °C and initial pH 12.0 without pH control to investigate the characteristics of casein–glucose Maillard reaction and the antioxidant activity difference among different fractions of MRPs. Browning and intermediate products increased, however, the pH of the system decreased with increase in the heating time. Free amino group content decreased 78% during first 10 min and did not change nearly thereafter. Amino acid analysis indicated that lysine and arginine decreased significantly, and casein was partially hydrolysed to peptides or free amino acid. High molecular weight compounds were dominant in the MRPs, determined by high performance gel-filtration chromatography. After ultrafiltration, antioxidant activity of each MRPs fraction was investigated by DPPH radical-scavenging activity, reducing power, Fe 2+ chelating activity and lecithin oxidation assay. MRPs of different molecular weight exhibited distinctly different antioxidant activities.

Protein glycation inhibitory activities of Lawsonia inermis and its active principles

The protein glycation inhibitory activity of ethanolic extract of Lawsonia inermis (henna) plant tissues was evaluated in vitro using the model system of bovine serum albumin and glucose. Protein oxidation and glycation are posttranslational modifications that are implicated in the pathological development of many age-related disease processes. This study investigated the effects of Lawsonia inermis ethanolic extract and its components, on protein damage induced by a free radical generator in in vitro assay system. We found that alcoholic extract of Lawsonia inermis can effectively protect against protein damage and showed that its action is mainly due to Lawsone. In addition, the presence of gallic acid also plays an important role in the protective activity against protein oxidation and glycation. Two known compounds, namely, Lawsone and gallic acid previously isolated from this plant were subjected to glycation bioassay for the first time. It was found that the alcoholic extract, lawsone (1) and gallic acid (2) showed significant inhibition of Advanced Glycated End Products (AGEs) formation and exhibit 77.95%, 79.10% and 66.98% inhibition at a concentration of 1500 μg/mL, 1000 μg/mL and 1000 μM respectively. Lawsonia inermis, compounds 1 and 2 were found to be glycation inhibitors with IC50 82.06 ± 0.13 μg/mL, 67.42 ± 1.46 μM and 401.7 ± 6. 23 μM respectively. This is the first report on the glycation activity of these compounds and alcoholic extract of Lawsonia inermis.

The kinetics of acrylamide formation/elimination in asparagine–glucose systems at different initial reactant concentrations and ratios

The effect of initial reactant concentration and ratio on the kinetics of acrylamide formation and elimination was studied using diluted asparagine–glucose model systems, heated at temperatures between 120 and 200 °C. By means of single response modelling, acrylamide concentrations measured could be modelled using a simplified kinetic model, in which acrylamide formation and elimination reactions were included. Changing the reactant concentration in equimolar systems did not affect significantly the kinetic parameters ( k Fref and E aF) for acrylamide formation, whereas the rate constant for acrylamide elimination increased with increasing reactant concentration, in the range from 0.01 M to 0.125 M. Modifying the reactant ratio, while keeping one of the reactants at a fixed concentration (0.125 M), did not affect the estimated parameters as compared to the equimolar system. In addition, multiresponse modelling was applied on three model systems with a different initial reactant ratio. Besides acrylamide, the concentration of the reactants and fructose and the level of browning were quantified. By means of deduction, a mechanistic model was proposed which was able to model all responses simultaneously in an adequate way. It appeared that caramelisation has a predominant role in browning, however, only in the system with an excess of sugar. The corresponding kinetic parameters estimated were in some cases significantly different, but in the same order of magnitude.

Reduction of Acrylamide and Its Kinetics by Addition of Antioxidant of Bamboo Leaves (AOB) and Extract of Green Tea (EGT) in Asparagine–Glucose Microwave Heating System

This study investigated the effect of antioxidant of bamboo leaves (AOB) and extract of green tea (EGT) on the formation and kinetics of acrylamide in an equimolar asparagine-glucose model system. The substrates spiked with AOB and EGT were microwave-heated at 180 degrees C and the acrylamide content in final reaction products was quantified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that both AOB and EGT could effectively reduce the formation of acrylamide in an asparagine-glucose microwave heating model system and achieved a maximum reduction rate when the addition levels of AOB and EGT were both 10(-6) mg/mL reaction solution. To describe the kinetic behavior of acrylamide, a simplified kinetic model was optimized and relative kinetic rate constants were evaluated under isothermal conditions. The results indicated that the reduction effect of AOB and EGT on the acrylamide formation may partly be ascribed to the decrease of the formation rate constant (k(F)) in both AOB and EGT-spiked systems (43.4% and 32.3% of decrease, respectively, P < 0.05). The kinetic parameter k(E), which represents the elimination rate of acrylamide in both AOB and EGT-spiked systems, was not significantly different (6.9% of increase and 10.9% of decrease, respectively, P > 0.05). The results of the kinetic study indicated that addition of AOB and EGT could significantly reduce the formation rate constant (k(F)) of acrylamide, but could not significantly affect the elimination rate constant (k(E)) of acrylamide.

Effect of natural antioxidants on kinetic behavior of acrylamide formation and elimination in low-moisture asparagine–glucose model system

The present study investigated the effect of two natural antioxidants, i.e. antioxidant of bamboo leaves (AOB) and extract of green tea (EGT), on the mitigation and the kinetic behavior of acrylamide in an equimolar asparagine–glucose model system (pH 6.80). The substrates with addition of AOB or EGT were oven-heated at 180 °C under low-moisture conditions and the acrylamide content in final reaction products was quantified by ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS). Results of mitigation effect on the generation of acrylamide showed that both AOB and EGT could effectively reduce the formation of acrylamide and achieve a maximum reduction rate (74.4% for the use of AOB and 74.3% for the use of EGT) when the addition levels of AOB and EGT were both 10 −4 mg. Such mitigation effect in the model system was further confirmed by addition of homoorientin and epigallocatechin gallate (EGCG), the representative components in AOB and EGT. To describe the kinetic behavior of acrylamide, a logistic-exponential model was selected among three kinetic model candidates while relative kinetic rate constants were calculated by the Marquardt non-linear regression method. Results indicated that there were significant differences on kinetic parameters ( k g and t cg) between AOB/EGT-spiked and non-spiked model system studies, which suggested that addition of AOB or EGT could reduce the formation of acrylamide during the formation-predominant kinetic stage and prolong the formation progress of acrylamide in the low-moisture reaction system. However, such addition method was not able to reduce the acrylamide content during the elimination-predominant kinetic stage of acrylamide.

Functional properties of melanoidins: In vitro antioxidant, antimicrobial and antihypertensive activities

Abstract Melanoidins formed at the last stage of the Maillard reaction have been pointed out to possess certain functional properties such as antioxidant, antimicrobial and antihypertensive activities. In order to gain more insights on these functional properties different soluble melanoidins and melanoidin fractions isolated from several amino acid–glucose model systems has been analysed In the case of antioxidant and antimicrobial properties, low molecular weight compounds bounded to melanoidins (BMC fraction) exerts antioxidant and antimicrobial activities usually higher than those of the pure melanoidins to whom they are linked. Contrary, in the case of antihypertensive activity it has been found that the main activity is related to the melanoidin core, not to BMC fraction. In addition it has been found no correlation, except for ABTS assay, among colour and antioxidant, antimicrobial or antihypertensive activity, supporting the idea that melanoidin chromophores are not responsible for these actions.

Characteristics and antioxidative activity of Maillard reaction products from a porcine plasma protein–glucose model system as influenced by pH

Maillard reaction products (MRPs) were prepared by heating the solution containing 2% porcine plasma protein (PPP) and 2% glucose adjusted to various pHs (8, 9, 10, 11 and 12) at 100 °C for different times (0, 2, 4, 6 and 8 h). The pH of all MRPs markedly decreased within 2 h of heating time. Browning and intermediate products, as monitored by absorbance at 420 nm and absorbance at 294 nm, sharply increased within 2 h ( P < 0.05). Thereafter, slight increases were observed up to 8 h. Fluorescence intensity (Ex 347 and Em 415 nm) sharply increased within the first 2 h with a subsequent decrease when heating time increased ( P < 0.05). Increases in browning and formation of intermediate products were concomitant with the decreases in free amino group and reducing sugar contents. Among all MRPs tested, those derived from the PPP–glucose system at pH 12 rendered the highest browning and intermediate products. However, no differences in reducing power or DPPH radical-scavenging activity of MRPs with initial pH ranges of 10–12 were noticeable. Electrophoretic study revealed that cross-linked proteins with high molecular weight were formed in the PPP–glucose model system to a greater extent at pHs 8 and 9, than at pHs 10–12. Nevertheless, heating times had no pronounced effect on protein pattern of glycated proteins.

Mechanism of Formation of Redox-Active Hydroxylated Benzenes and Pyrazine in 13C-Labeled Glycine/d-Glucose Model Systems

To extend the analytical capabilities of the pyrolysis-gas chromatograph-mass spectrometry system that has been successfully utilized in the past as an integrated reaction, separation, and identification system to study label incorporation patterns in Maillard reaction products, a novel methodology was developed to analyze the composition of nonvolatile residues of the initial reaction products. This was achieved through a postpyrolytic in-situ derivatization technique using trimethylsilyldiethylamine. Application of this technique to the investigation of the nonvolatile products formed during pyrolysis of glucose alone and in the presence of glycine has indicated the formation of several redox-active hydroxylated benzene derivatives such as 1,2,3-trihydroxybenzene (pyrogallol), 1,4-dihydroxybenzene (hydroquinone), 1,2-dihydroxybenzene (catechol), and 2,5-dihydroxypyrazine. Labeling studies have indicated that the intact glucose carbon backbone was involved in the construction of the benzene ring of the hydroxylated benzene derivatives and that dimerization of glycine alone can lead to the formation of 2,5-dihydroxypyrazine.

Reactivity of Epicatechin in Aqueous Glycine and Glucose Maillard Reaction Models: Quenching of C2, C3, and C4 Sugar Fragments

Mechanisms of how epicatechin alters the pathways of the Maillard reaction were investigated. Carbon-13 and nitrogen-15 labeling studies were utilized to define the reactivity of epicatechin with glucose, glycine, and/or reaction products in an aqueous model (pH 7, 125 degrees C for 30 min) via GC, GC/MS and HPLC/MS analysis. Quantification of the volatile reaction product isotopomers by GC/MS from a 1:1 labeled to unlabeled glucose (carbohydrate module labeling technique) plus glycine model system indicated the formation of 2,3-butanedione and acetol were primarily formed via intact C4 and C3 sugar fragments, whereas pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and cyclotene were primarily formed via intact C2/C2, C2/C3, C3/C3, C3/C3, and C3/C3 sugar fragment pairs, respectively. The formation of these seven compounds was also reported by GC analysis to be dramatically inhibited when epicatechin was added to the glucose/glycine model system (observed 9-113-fold reduction). HPLC/MS analysis of both the glucose-labeled and glycine-labeled model systems with and without epicatechin indicated that epicatechin reacted directly with C2, C3, and C4 sugar fragments, while epicatechin did not report any direct reactivity with glycine. In conclusion, the quenching of sugar fragmentation products via epicatechin was correlated with the observed inhibition on volatile compound formation when epicatechin was added to a glucose/glycine aqueous reaction model system.

Characterization of coloured compounds obtained by enzymatic extraction of bakery products

Melanoidins, the brown-colored polymers formed through Maillard type reaction in several heat-treated foods, represent a significant part of our diet, with an average intake of grams per day. Most of the studies on the physiological effects of these compounds have been performed using the water soluble melanoidin fractions. But dietary melanoidins formed on the surface of bakery products are poorly soluble in water as well as in organic solvents. In this work, an enzymatic solubilization procedure was developed on a gluten–glucose model system and it was applied to bread and biscuits. The soluble material obtained was tested for its antioxidant activity, for its effect on phase-I and phase-II xenobiotic enzymes and for potential cytotoxic effects. Soluble melanoidins from model system and biscuits exhibit a strong antioxidant activity and do not show any cytotoxicity on Caco-2 cells. Melanoidins extracted from biscuits was able to inhibit the activity of Phase I (NADPH-cytochrome-c reductase) and Phase II (Glutathione- S-transferase) enzymes, whereas the low molecular weight melanoidins isolated from gluten–glucose model system inhibit the activity of NADPH-cytochrome-c reductase.

Formation of Strecker aldehydes and pyrazines in a fried potato model system.

Sugars and amino acids were removed from potato slices by soaking in water and ethanol. They were then infused with various combinations of sugars (glucose and/or fructose) and amino acids (asparagine, glutamine, leucine, isoleucine, phenylalanine, and/or methionine) and fried. Volatile compounds were trapped onto Tenax prior to gas chromatography-mass spectrometry. Relative amounts of compounds (relative to the internal standard) and relative yields (per mole of amino acid infused into the slices) were determined. Amounts of 10 pyrazines, 4 Strecker aldehydes, and 4 other compounds were monitored. Relative amounts and relative yields of compounds varied according to the composition of the system. For the single amino acid-glucose systems, leucine gave the highest relative amount and relative yield of its Strecker aldehyde. Asparagine and phenylalanine gave the highest total relative amount and total relative yield, respectively, of pyrazines. In the system containing all of the amino acids and glucose, the relative amount of 3-methylbutanal was higher, whereas the amounts of the other monitored Strecker aldehydes were lower. Most of the relative amounts of individual pyrazines were lower compared to the glucose-asparagine system, whereas the total relative yield of pyrazines was lower, compared to all of the single amino acid-glucose mixtures. Addition of fructose to the mixed amino acid-glucose model system generated Strecker aldehydes and pyrazines in ratios that were more similar to those of untreated potato chips than to those from the same system but without fructose. Both the sugars and the amino acids present in potato are crucial to the development of flavor compounds in fried potato slices.

Formation of Heterocyclic Amines in a Model System during Heating

The formation of heterocyclic amines (HAs) in a model system during heating at 100, 150, or 200°C for varied lengths of time was studied. The following systems were used: (i) phenylalanine, (ii) creatinine, (iii) phenylalanine and glucose, (iv) phenylalanine and creatinine, (v) glucose and creatinine, and (vi) phenylalanine, glucose, and creatinine. Results showed that HAs could only be found in both systems of glucose and creatinine, and of phenylalanine, glucose, and creatinine. Both 2-amino-9H-pyrido-[2,3-b]indole (AαC) and 2-amino-3-methyl-9H-pyrido-[2,3-b]indole (MeAαC) were observed in the former system, and the formation rate of AαC was higher than MeAαC. For the latter system, 2-amino-3-dimethylimidazo[4,5-f]quinoxaline (IQx), 9H-pyrido-[4,3-b]indole (Norharman), 1-methyl-9H-pyrido-[4,3-b]indole (Harman), AαC, and MeAαC were present. The formation rate of AαC was the highest at 200°C, followed by MeAαC, Harman, Norharman, and IQx. In addition, the varieties of HAs increased both with increasing heating time and temperature. The amounts of HAs formed were less in the model system of glucose and creatinine than that of phenylalanine, glucose, and creatinine. The same trend was also observed for the formation rate of HAs. At 150 or 200°C, the amounts of IQx, Harman, Norharman, AαC, and MeAαC increased in the initial period of heating and then reached a plateau. The results of this study provided a basic understanding of the conditions that result in the formation of HAs during cooking of meat and fish products.