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

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, Fe²⁺ chelating activity and lecithin oxidation assay. MRPs of different molecular weight exhibited distinctly different antioxidant activities.     

Purification and identification of antioxidant peptides from corn gluten meal

Corn gluten meal was hydrolyzed by alkaline protease and Flavourzyme to obtain the antioxidant peptides. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging capacity (1,1-diphenyl-2-picrylhydrazyl/2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt/hydroxyl radical/superoxide radical anion), metal ion (Fe²⁺/Cu²⁺) chelating activity and lipid peroxidation inhibitory capacity. The hydrolysates were separated by ultrafiltration, and those with molecular weight <10 kDa exhibited highest antioxidant activity in all relevant assays. The hydrolysates were subsequently purified by gel filtration chromatography, and fraction F3 showed the highest antioxidant activity. Three peptides were identified from fraction F3 using LC–ESI–Q–TOF MS/MS as Leu-Pro-Phe (375.46 Da), Leu-Leu-Pro-Phe (488.64 Da) and Phe-Leu-Pro-Phe (522.64 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. Thus, corn gluten meal may be used as a potential source of antioxidant peptides for food and nutraceutical applications.     

Antioxidant and antiradical properties of maillard reaction products in both aqueous and ethanolic fructose-glycine oligomer solutions

The purpose of this study was to evaluate the antioxidant and antiradical properties of Maillard reaction products (MRP) in both aqueous and ethanolic fructoseglycine oligomer solutions. Antioxidant and radical scavenging activities of MRPs were investigated using different in vitro assays: the ferric ion (Fe³⁺) reducing ability, cupric ion (Cu²⁺), ferrous ion (Fe²⁺) chelating effects, DPPH and ABTS radical scavenging activities, and Fe³⁺-TPTZ reducing ability. MRPs derived from fructose-diglycine (GG) were found to be effective antioxidants in different in vitro assays. The antioxidant activity was higher in ethanolic solutions than in aqueous MRP solutions.     

Structure and antioxidant activity of high molecular weight Maillard reaction products from casein–glucose

Maillard reaction products (MRPs) were prepared from a casein–glucose reaction and ultrafiltrated to provide six fractions. The high molecular weight glycated proteins (melanoprotein) were further purified with a Sephadex G-75 column. Two fractions were obtained and analysed for their reducing power and Fe²⁺ chelating activity. Results obtained from the first fraction, analysed by Fourier transform infrared spectroscopy (FT-IR) indicated that the amide I, II and III bands of casein were changed by the Maillard reaction. The obtained samples were also hydrolysed with pepsin and trypsin in vitro, and the proteolytic hydrolysates were evaluated for their antioxidant activities. Non-hydrolysed melanoproteins exhibited the highest reducing power, but peptic hydrolysates of different MRPs were more efficient in radical-scavenging activity.     

Effect of substrate ratios and temperatures on development of Maillard reaction and antioxidant activity of silver carp (Hypophthalmichthys molitrix) protein hydrolysate–glucose system

The study of antioxidant activity of the hydrolysates is necessary during its processing in which Maillard reaction would often occur. To understand the effect of Maillard reaction on antioxidant activity of silver carp protein hydrolysates (SPH), the Maillard reaction products (MRPs) were prepared at different ratios between SPH and glucose by Maillard reaction in powdered state, respectively. MRPs possessed a strong 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity and reducing power (P < 0.05). The hydrolysate and glucose heated with the ratio of 2:1 at 60 °C showed high browning intensity and good antioxidant properties (P < 0.05). According to the correlation coefficients of variables included in the hydrolysate–glucose system, good correlations were observed among the antioxidant activities, the absorbance at 294 nm and the loss of free amino groups. The results suggested that Maillard reaction has a good potential to improve the antioxidant activity of SPH.     

Impact of electro-activation on antioxidant properties of defatted whey

Antioxidant activity of electro-activated whey (EA-whey) was investigated. The effects of electric current intensity (400, 500 or 600 mA) and whey total solids concentration (7, 14 or 21%, w/v) as a function of reaction time (0, 15, 30 or 45 min) on antioxidant properties of defatted whey were studied. The extent of current intensity and reaction times were the most significant parameters (P < 0.001). Oxygen radical absorbance capacity and 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical scavenging activities of the EA-whey were significantly increased by the formation of Maillard reaction products (MRPs). Moreover, EA-whey possessed reducing power and strong Fe²⁺ chelating ability. The MRPs derived from the EA-whey with 14% total solids concentration had the highest hydroxyl radical scavenging activity. The findings indicate the potential of electro-activation technology to enhance the functional proprieties of whey; EA-whey could be used in the food industry as a natural antioxidant ingredient to replace synthetic antioxidants.     

Effect of amino acids on Maillard reaction product formation and total antioxidant capacity in white pan bread

Maillard reaction products (MRPs) can be an important dietary antioxidant source. Bread is the most popular bakery product; however, limited information is available on the antioxidant activities of MRPs generated during bread-baking. This paper reports the effect of different amino acids on bread properties, melanoidin formation and antioxidant activities. Totally six amino acids at four different levels were evaluated. Increasing the amount of amino acid led to darker bread crust, higher melanoidin content and stronger antioxidant activity. Among the six amino acids, bread with glycine had the highest melanoidin content and ABTS radical scavenging activity up to 1079.77 ± 8.43 μmol TE mg⁻¹. Bread with lysine had the highest DPPH radical scavenging activity up to 281.97 ± 10.52 μmol TE mg⁻¹. Bread with alanine had the highest crust metal chelating activity compared with others. Adding certain dietary amino acids is a potential approach to enhance the antioxidant capacity of bread products.     

Influence of pH on the formation and radical scavenging activity of volatile compounds produced by heating glucose with histidine/tyrosine

In this study, the effect of pH on the volatile generation over reaction time as well as the DPPH radical scavenging activity of volatile MRPs was investigated in the Maillard reaction of glucose (Glc) with tyrosine (Tyr) and histidine (His). Factor analysis showed clearly that volatiles generated in 5-h open system were of similar composition to those in 0.5-h close system regardless of pH level and amino acid, implying higher pressure in close system could accelerate the volatile formation in Maillard reaction. Besides, all volatiles showed increasing tendency over reaction time under different pH levels with the exception of pyrones which decreased with the extension of reaction time at pH = 7 and pH = 9. Furans, phenols and 2-acetylpyrrole that were favored under acidic condition showed larger increase at pH = 5 over reaction time, while other volatiles except pyrones, furans, phenols and 2-acetylpyrrole, which were favored under neutral and alkaline conditions, showed greater increase at pH = 7 and pH = 9 over reaction time. The measurement of DPPH radical scavenging activity of dichloromethane extract obtained from Maillard reaction mixture revealed that volatile MRPs from Glc–Tyr system showed stronger antioxidant activity under alkaline condition, while volatile MRPs from Glc–His system showed greater antioxidant activity under acidic condition.     

Characteristics and antioxidant activity of Maillard reaction products from fructose-glycine oligomer

The pH of Maillard reaction products (MRPs) derived from the Gly model system (Gly) decreased markedly as heating time increased. However the Digly model system (Digly) exhibited the highest increase in absorbance at 294 and 420 nm. Moreover, the loss of fructose and degree of sugar enolization in MRPs derived from the Trigly model system (Trigly) was the highest, whereas the glycine oligomer content in the Digly noticeably decreased as heating time increased. Furthermore, the gel permeation chromatograms (GPC) patterns of all MRP samples exhibited rising intensities as a function of the heating time, whereas the major peaks of each MRP sample were eluted at different retention times as glycine oligomer. Antioxidant activity of each MRP sample was investigated by Fe²⁺ and Cu²⁺ chelating activity, Trolox, ABTS, 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging activity, and ferric reducing ability of plasma (FRAP) assay. MRPs derived from the glycine oligomer were found to be effective antioxidants in different antioxidant activity assays.     

酪蛋白-木糖体系美拉德反应产物的抗氧化活性

研究评价了由酪蛋白-木糖模拟体系产生的美拉德反应产物的抗氧化活性,考察了反应过程中体系的pH、褐变和中间产物的变化,并测定了美拉德反应产物对金属离子(Cu2+和Fe2+)的螯合能力、自由基清除能力(.OH、DPPH.和ABTS.)以及其还原能力。结果表明,模拟体系的酸度和褐变均随反映的进行而逐渐增加,中间产物在反应初期大量形成;美拉德反应产物对Fe2+的螯合能力要明显强于对Cu2+的螯合能力;美拉德反应产物对DPPH.和ABTS.具有较强的清除作用,而对.OH的清除作用较弱;美拉德反应产物的还原能力随反应时间的延长而逐渐增大。     

Antioxidant activity of Maillard reaction products derived from aqueous glucose/glycine,diglycine, and triglycine model systems as a function of heating time

The purpose of this study was to evaluate the antioxidant activity of Maillard reaction products (MRPs) derived from aqueous glucose/glycine, diglycine, and triglycine model systems as a function of heating time. The pH of MRPs derived from the Glu-G model system decreased markedly as the heating time increased, while MRPs derived from the Glu-Di model system showed the highest increase in absorbance at 420 nm. MRPs derived from the Glu-G model system showed the highest cupric ion chelating ability, while MRPs derived from the Glu-Di model system had the highest ferrous ion chelating activity. MRPs derived from the Glu-Di model system were found to be effective antioxidants in different in vitro assays with regard to the 2,2′-azinobis(3-ethylbenothiazoline-6-sulphonic acid) diammonium salt (ABTS) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging activities and ferric reducing/antioxidant power (FRAP).     

Determination of the molecular weight distribution of non-enzymatic browning products formed by roasting of glucose and glycine and studies on their effects on NADPH-cytochrome c-reductase and glutathione-S-transferase in Caco-2 cells.

After thermal treatment of a mixture of glucose and glycine for 2 h at 125 degrees C, about 60% of the starting material was converted into non-soluble, black pigments, whereas 40% of the mixture was still water-soluble. Dialysis of the latter fraction revealed 30.4% of low molecular weight compounds (LMWs; MW < 10,000 Da) and 10.0% high-molecular weight products (HMWs; MW > or = 10,000 Da). The water-soluble Maillard reaction products (MRPs) were separated by gel permeation chromatography and ultrafiltration, revealing that 60% of the water-soluble products of the total carbohydrate/amino acid mixture had MWs < 1,000 Da and consisted mainly of non-coloured reaction products. MRPs with MWs between 1,000 and 30,000 Da were found in comparatively low yields (about 1.3%). In contrast, about 31.1% of the MRPs exhibited MWs > 30,000 Da, amongst which 14.5% showed MWs > 100,000 Da, thus indicating an oligomerisation of LMWs to melanoidins under roasting conditions. To investigate the physiological effects of these MRPs, xenobiotic enzyme activities were analysed in intestinal Caco-2 cells. For Phase-I NADPH-cytochrome c-reductase, the activity in the presence of the LMW and HMW fraction was decreased by 13% and 22%, respectively. Phase-II glutathione-S-transferase activity decreased by 15% and 18%, respectively, after incubation with the LMW and the HMW fractions. Considering the different yields, 30% and 10%, respectively, of the LMW and the HMW fractions, the total amount of the LMW fraction present in the glucose-glycine mixture is more active in modulating these enzyme activities than that of the HMW fraction.     

Comparison of Physicochemical and Antioxidant Properties of Egg-White Proteins and Fructose and Inulin Maillard Reaction Products

The Maillard reaction (MR), involving the condensation of a carbonyl group of reducing sugar and an amino group of protein, can change functional properties of proteins. In this study, chemical characteristics and functional properties of glycosylated albumin, ovomucoid, and lysozyme (egg proteins) and casein with fructose or inulin through the MR were evaluated. The protein and sugar mixtures were heated at 60 °C and 79% relative humidity for 3 days. Chemical characteristics of the egg protein–sugar Maillard reaction product (MRP) mixtures were evaluated by fluorescence development, absorbance intensity (at 420 nm), and color change. Functional properties of the protein–sugar MRP mixtures were also evaluated, including emulsifying activity, emulsion stability, and antioxidant activity. The protein–sugar conjugates were found to have significant (p < 0.05) changes compared to the controls (unheated protein–sugar samples) in color, fluorescence, and absorbance intensity. All protein–sugar MR models exhibited a change in emulsifying activity, with Csn–Fru MRP displaying the greatest significant (p < 0.05) improvement. In addition, all protein–sugar MR models exhibited changes in emulsion stability, with Ovo/Inu MRP displaying the greatest significant (p < 0.05) change. All protein–sugar MR models exhibited great scavenging activity towards 1,1-diphenyl-2-picryl-hydrazyl radical at MRP concentrations of 0.2, 0.5, and 1.0 mg/mL. With the exception of the 0.2 mg/mL MRP concentration, there was a significant difference (p < 0.05) between the heated protein–fructose and the heated protein–inulin MRPs.     

Antioxidant activity of lignans from fringe tree (Chionanthus virginicus L.)

Fringe tree (Chionanthus virginicus L.), a shrub of the eastern part of America, used as a raw material by pharmaceutical industries for cholagoque, diuretic, tonic and the preparation of homeopathic tinctures. The identification of lignans as major antioxidant components and determination of their antioxidant activities are of considerable interest, because of the role they play in pharmacological actions. The potential antioxidant activity of the lignans such as phillyrin, pinoresinol-β-d-glucoside (PDG) and pinoresinol di-β-d-glucoside (PDDG) from root bark of fringe tree (C. virginicus L.) were examined by different antioxidant tests including; 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH^•) scavenging, superoxide anion radical (O₂ ^•-) scavenging, total antioxidant activity by ferric thiocyanate method, reducing activity by Fe³⁺–Fe²⁺ transformation, hydrogen peroxide (H₂O₂) scavenging and ferrous metal (Fe⁺²) chelating activities. Phillyrin, PDG and PDDG, as antioxidants, neutralized the activities of radicals and inhibited the peroxidation reactions of linoleic acid emulsion. The total antioxidant activity was determined according to the ferric thiocyanate method. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox, which is a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. Phillyrin, PDG and PDDG showed 67.6, 77.3 and 64.2% inhibition on lipid peroxidation of linoleic acid emulsion, respectively, at the concentration of 20 μg/mL. On the other hand, BHA, BHT, α-tocopherol and trolox exhibited 74.4, 71.2, 54.7 and 20.6% inhibition on peroxidation of linoleic acid emulsion, respectively, at the above mentioned concentration. In addition, phillyrin, PDG and PDDG were effective on DPPH^•, ABTS^•+ and O₂ ^•- scavenging, H₂O₂ scavenging, total reducing power and metal chelating effect on ferrous ions activities. Also, BHA, BHT, α-tocopherol and trolox were used as references antioxidants for these various antioxidant activities.     

草鱼抗氧化肽的美拉德反应特性研究

本研究通过单独加热草鱼肽和添加木糖加热反应制备热降解产物（TDPs）和美拉德反应产物（MRPs),运用DPPH?抑制率、肽分子量分析及氨基酸分析等方法评价不同反应时间草鱼肽热降解产物及美拉德反应产物的抗氧化性能、分子量分布以及氨基酸组成的变化规律,深入探讨了反应时间对草鱼肽的美拉德反应产物特性的影响。研究发现,单独加热草鱼肽对各时间段热降解产物的总氨基酸含量无显著影响,游离氨基酸含量显著增加,而3000 Da以下肽段含量增多。美拉德反应体系样品随着反应时间的增加,产物中总氨基酸及游离氨基酸含量下降,其中精氨酸及赖氨酸减少尤其显著,分子量大于3000 Da的肽段明显增多,3000 Da以下的肽段含量降低,此外,美拉德反应产物中抗氧化活性显著增强。     

Transglutaminase cross-linking effect on sensory characteristics and antioxidant activities of Maillard reaction products from soybean protein hydrolysates

To improve the yield of Maillard peptides, a microbial transglutaminase (MTGase) was used to increase the content of 1000–5000 Da peptides in soybean protein hydrolysates by using a cross-linking reaction. The sensory characteristics and antioxidant activities of corresponding Maillard Reaction Products (MSPC) was then evaluated. After cross-linking treatment the content of 1000–5000 Da peptides in protein hydrolysates and the yield of Maillard peptides increased by 21.19% and 8.71%, respectively, which contributed to the improved mouthfulness of MSPC. The bitter amino acids were significantly decreased and the umami acids were markedly increased in MSPC. Volatile compounds identified by GC–MS analysis showed that the content of the important meaty flavour compounds (such as 2-methyl-3-furanthiol, bis(2-methyl-3-furyl)disulfide) of MSPC were dramatically higher than that of MRPs from uncross-linking peptides. Combined with sensory evalution, it was confirmed that MTGase cross-linking improved the flavour Characteristics and did not affect the antioxidant activity of MSPC.     

Optimization of Maillard reaction products from casein-glucose using response surface methodology

Response surface methodology (RSM) was applied to optimize the processing parameters of casein-glucose Maillard reaction for improving the emulsifying ability and antioxidant activity. The effect of heating time, temperature and initial pH on Maillard reaction products (MRPs) was evaluated. Emulsifying ability and reducing power were taken as response values. An increase of temperature in range and initial pH were associated with an enhanced emulsifying ability and reducing power of the MRPs. Substrate concentration 20%, casein-glucose ratio 1:2, heating time 132.7 min, temperature 100.2 °C and initial pH 12.0 were optimum conditions for the improved emulsifying ability and antioxidant activity of the MRPs. The predicated results for optimum reaction conditions coincided well with experiments values.     

Heat-induced Maillard reaction of the tripeptide IPP and ribose: Structural characterization and implication on bioactivity

Maillard reaction products (MRPs) were prepared from aqueous model mixtures containing 60 g L^? 1 ribose and 30 g L^? 1 of the bioactive tripeptide IPP (Ile-Pro-Pro), heated at 98 °C. MRP and associated reactions with changes in IPP were observed within one hour of heat-treatment. The pH of MRPs decreased significantly during the heat treatment of IPP–ribose mixtures from 9.0 to 7.6 after one hour. The amino group content, IPP and ribose concentration decreased significantly during heat treatment. The fluorescence intensity of the IPP–ribose MRPs reached the maximum within 2 h. Modification of the UV/vis spectra for IPP–ribose MRPs was mainly due to a condensation reaction of IPP with ribose. Compounds with molecular weight between 300 and 650 Da were dominant while compounds smaller than 250 Da were also produced during the reactions, as characterized by size exclusion chromatography. Mass spectrometry revealed that IPP was conjugated to ribose at the N-terminal (m/z of 458.3) upon heat-treatment. The presence of ribose also promoted peptide degradation to dehydrated IP (m/z of 211.1). IPP–ribose MRPs lost the known angiotensin-I-converting enzyme (ACE) inhibitory activity of IPP; however, strong antioxidant properties were detected.     

Evaluation of Antioxidant Activities of Zein Protein Fractions

Zein protein was extracted from the by‐product corn gluten meal. The obtained zein protein was 1st hydrolyzed by 4 different proteases. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging activity, metal ion chelating activity, and lipid peroxidation inhibitory capacity. Among hydrolysates produced, alkaline protease hydrolysates exhibited the highest antioxidant activity. A regression model was established by uniform design to optimize the alkaline protease hydrolysis conditions. The hydrolysates with molecular weight < 3 kDa obtained from ultrafiltration showed the highest antioxidant activities in all relevant assays. The hydrolysates with molecular weight <3 kDa were subsequently purified by gel filtration chromatography, and fraction F3 exhibited the highest antioxidant activities. Two peptides were identified from fraction F3 using LC‐ESI‐Q‐TOF MS/MS as Pro‐Phe (263.13 Da) and Leu‐Pro‐Phe (375.46 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. The results clearly indicated that zein protein fractions are good sources for the development of natural antioxidants for the food industry.