Confirmation that the Maillard reaction is the principle contributor to the antioxidant capacity of coffee brews

Chemical characteristics related to the antioxidant activity of roasted coffee (RC) were evaluated, using non-roasted coffee beans (NRC) and model Maillard reaction products (MRPs) as controls. The formation of MRPs and the degradation of phenolics in RC were characterized by employing a battery of fluorescence, UV-vis spectra and tri-stimulus color parameters measured on NRC, RC and the model MRPs. Total chlorogenic acid (CGA) and caffeine contents in NRC and RC extracts were also quantified using HPLC. Both RC and controls showed high antioxidant activity in three chemical based assays irrespective of caffeine content. Data from this study suggested that natural phenolics present in NRC had higher antioxidant activity compared to MRPs derived from coffee and model MR systems. However, MRPs were the prevailing antioxidants in RC as free CGA was lost (> 90%). The mechanisms of the antioxidant action associated with coffee MRPs involved hydrogen atom transfer and single electron transfer mechanisms.     

Identification of hydrogen peroxide as a major cytotoxic component in Maillard reaction mixtures and coffee

The cytotoxic activity of Maillard reaction products and coffee was studied using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐tetrazolium bromide (MTT) assay and the neutral red uptake (NRU) assay. Equimolar mixtures of sugars and lysine were heated at 120°C and used to stimulate bovine aorta endothelial cells for 24 h. The cytotoxic activity increased with increase in educt concentration and heating time. Mixtures containing ribose were most active, followed by lactose and glucose. Hydrogen peroxide, which was present in the Maillard mixtures in concentrations between 7 and 87 μM, was identified as one of their major cytotoxic components. H₂O₂‐concentrations increased further up to 130 μM under cell culture conditions. Filter coffee, espresso, and green coffee extract reduced cell viability significantly to 10, 19, and 83% of PBS‐treated control. The effect was largely attenuated by the addition of catalase. Nil, 33, and 41 μM H₂O₂ was measured in green coffee extract, filter coffee, and espresso, respectively, increasing to 13, 369, and 333 μM during cell culture conditions. No additional H₂O₂ formation was detected when coffee was incubated for up to 5 h without further treatment. In conclusion, hydrogen peroxide is a major product in Maillard mixtures and coffee inducing cell death in vitro.     

Identification of aminoreductones as active components in Maillard reaction mixtures inducing nuclear NF‐κB translocation in macrophages

Coffee, a highly processed food, and Maillard mixtures are able to activate nuclear factor κB translocation in macrophages via generation of hydrogen peroxide. In this study, a substructure library was prepared and used to identify Maillard products that are responsible for this effect. Three different Maillard reaction products with aminoreductone substructure (C₆‐aminoreductone, C₄‐aminoreductone, and aminohexose reductone) strongly induce nuclear factor κB translocation in macrophages. The effect was almost completely blocked by co‐incubation with catalase, indicating that cellular activation was mediated by the ability of the test compounds to generate hydrogen peroxide. The cellular effect of a Maillard mixture, which was produced under conditions favoring aminoreductone formation, could be almost completely related to the presence of C₆‐aminoreductone.     

Interaction between Maillard reaction products and lipid oxidation in starch‐based model systems

The effect of Maillard reaction products (MRPs) on the kinetics of lipid oxidation in intermediate‐moisture model systems containing pregelatinised starch, glucose, lysine and soybean oil has been studied. The samples, either containing all components or excluding one or more of them, were heated at 100 °C for different times. Lipid oxidation and browning indices were measured and the results confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted, the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of MRPs was also evaluated using a peroxide‐scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples. © 2000 Society of Chemical Industry     

A diet rich in Maillard reaction products protects LDL against copper induced oxidation ex vivo, a human intervention trial

Maillard reaction products (MRPs) have antioxidative properties in vitro but the influence of a diet rich in MRPs on oxidative damage in vivo remains unknown.In this study, the influence of thermally processed foods rich in MRPs on copper induced oxidation of human low-density lipoprotein (LDL) in vitro was examined. Moreover, oxidative resistance of LDL (OR) in blood plasma of eight healthy subjects was monitored, who consumed diets poor and rich in MRPs in weekly turn for 3 weeks.Dark beer, bread crust, and roasted coffee led to a statistically significant increased OR in vitro compared to pale beer, bread crumb, and raw coffee. The consumption of a diet rich in MRPS significantly increased plasma OR compared to the diet poor in MRPs by 35.5%.This study indicates that thermally processed foods rich in MRPs inhibit the LDL oxidation in vitro and have the ability to reduce oxidative modification of LDL in vivo.     

美拉德反应产物(MRPs)对腊肠氧化稳定性的影响

研究了不同添加量的美拉德反应产物(MRPs)对腊肠POV值(过氧化值)、TBA值(硫代巴比妥酸值)和感官品质的影响。结果表明:与空白组比,添加MRPs能够显著抑制腊肠的氧化(p<0.05),并且随着MRPs添加量的增加,抑制腊肠氧化的能力显著增强(p<0.05),4%的MRPs与0.01%的BHT抑制腊肠氧化的能力相当(p>0.05)。通过感官评定得出,MRPs的添加对腊肠的综合得分影响不显著(p>0.05)。      

The inhibition effects of reactive oxygen species by Maillard reaction products in Caco‐2 cells

Maillard reaction products (MRPs) were prepared by heating a mixture of rice starch with different dextrose equivalents (DE 10, 30, 50 and 70) and glycine. The glycine was added to the sample pastes at the same molar concentration as the sugar contained in each sample. As the dextrose equivalent of rice starch increased, the browning intensity and fluorescence of the MRPs increased. The antioxidant properties of the MRPs were investigated by DPPH radical scavenging activity, reducing power, and phenolic content in a chemical system, and were evaluated by measuring reactive oxygen species levels and antioxidant enzymes activities in Caco‐2 cells. The darkest MRPs, MRPs‐4, showed the highest antioxidant activity and phenolic content among the samples; in addition, it inhibited the cellular oxidative stress. The decrease of cell viability and antioxidant enzymes activities caused by reactive oxygen species and apoptosis were recovered by MRPs‐4. Actually, the addition of the MRPs suppressed apoptosis by decreasing the proportion of cells in the sub‐G1 phase. Therefore, these MRPs, as compounds formed by the Maillard reaction, are considered to possess an effective antioxidant activity against oxidizable substrates.     

木糖- 甘氨酸美拉德反应体系光谱特性和抗氧化性能的研究

采用木糖和甘氨酸进行模式美拉德反应,考察反应进程中产物pH值、吸光度及颜色参数的变化,并以1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除能力、Fe2＋螯合能力及油脂过氧化值(POV)为指标,研究美拉德反应产物的抗氧化效果。结果表明：随着反应的进行,产物由无色变为蓝色最后生成褐色;反应pH值和L*值逐渐降低,a*值增大,b*值减小,但后期两者变化不显著。产物具有很好的Fe2＋螯合能力,POV值较低,但清除DPPH自由基能力不强。总体而言,产物具有较强的抗氧化能力。     

木糖与甘氨酸美拉德反应产物抗氧化性能的研究

以木糖和甘氨酸为底物,控制不同的物质的量(木糖与甘氨酸物质的量之比分别为1∶0.1、1∶0.2、1∶0.4)进行美拉德反应,制备了三种不同的美拉德反应产物,并通过还原能力、清除H2O2能力、清除羟基自由基(.OH)、清除超氧阴离子自由基(O2-.)、清除亚硝酸根(NO2-)等体系研究了美拉德反应产物的抗氧化性能。结果表明,三种反应产物均具有较强的抗氧化能力,随着反应产物浓度的增加,抗氧化能力增强;三种产物的还原能力和清除O2-.的能力相当;木糖与甘氨酸物质的量之比为1∶0.2的美拉德反应产物清除H2O2、.OH和NO2-的能力要强于物质的量之比为1∶0.1和1∶0.4的反应产物。     

酶法及美拉德反应改进鸡肉蛋白功能性质的研究

利用不同单酶酶解鸡胸肉,制得的酶解液和木糖进行美拉德反应,考察不同酶解方式制得的底物对美拉德反应产物的各检测指标(肽、氨基酸、糖等反应底物含量和美拉德产物含量及其抗氧化性能力)影响,并分析各检测指标间的相关性。实验表明:酶解程度对美拉德反应产物特性有显着性影响,酶解作用所得的肽具有更强的美拉德反应活性,酶解程度越大的酶解液,消耗糖量越多,生成的MRPs越多,其MRPs抗氧化活性越强,同一反应起始浓度,8 h与2 h酶解液的MRPs抗氧化能力相比,FRAP还原能力与DPPH·清除能力增强倍数高达2倍和7倍;美拉德反应能明显改善了酶解液的性质,可溶解性肽的含量最高增加了2倍,可溶性氨基酸最高增加了1倍,抗氧化能力最高增强了40倍;从检测指标的相关性可知,糖的消耗量变化一定程度上能反应美拉德反应的程度,美拉德反应能促进肽的分解生成氨基酸。     

Effect of Maillard reaction products prepared from glucose–glycine model systems on starch digestibility

The Maillard reaction is one of the most important phenomena occurring spontaneously during food processing and storage. However, research on the effects of Maillard reaction products (MRPs) on starch hydrolysis remains insufficient. To investigate the effects of MRPs on in vitro starch digestibility, the characteristics of glucose–glycine model system containing MRPs and digestive enzyme activities by MRPs were measured. MRPs were prepared by heating of glucose–glycine mixture solution at 90°C for different times (0, 1, 3, 9, 18, 24, and 48 h). As the Maillard reaction proceeded, browning intensity, and furosine and hydroxymethylfurfural content increased, whereas pH value decreased. The reducing power of MRPs was increased as the Maillard reaction progressed, and MRPs produced in 18 and 24 h showed the highest values (both 1.2). In MRPs heated for 48 h, the reducing sugar content and hydrolysis index were lowest values (88.6 and 87.0%) among the samples. The activity of digestive enzymes significantly decreased by adding of MRPs, as the browning of added MRPs increased. Therefore, MRPs seem to be contributed to decrease in starch digestibility, as shown by an enzymatic digestion result.     

Influence of pH,NaCl and pre‐incubation on utilisation of surimi wash water in generation of antioxidative material by using the Maillard reaction

Maillard reaction products (MRPs) were generated from reaction mixtures of surimi wash water (SWW) with glucose or fructose (5%w/v) heated at 95 °C for 2–12 h. The effects of pH, NaCl and pre‐incubation of SWW on the Maillard reaction and antioxidant capacity of MRPs were investigated. The antioxidative capacity of MRPs was determined by measuring free DPPH° radical scavenging activity and reducing power. The highest colour intensity (OD₄₂₀) as well as antioxidative capacity was noted in the reaction mixture containing fructose at pH 9.0. The addition of NaCl (0.5–2.5%w/v) caused reduction in browning intensity but enhanced antioxidative capacity of the MRPs. Pre‐incubation of SWW at 45 °C for 4 h decreased soluble protein but increased the Maillard reaction and antioxidative capacity of MRPs. A positive effect of salt or pre‐incubation of SWW on the antioxidative capacity of MRPs was not associated with the soluble protein content in the reaction mixture.     

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。     

湿热条件下低聚木糖-乳清分离蛋白的美拉德反应及产物乳化性与流变性研究

本文研究了湿热条件下不同混合质量比(1:1、1:2、1:3、1:4,W/W)对低聚木糖与乳清分离蛋白(WPI)美拉德反应及其产物的乳化性与流变性的影响。UV-Vis吸光度值,pH和粒径大小显著变化表明,该条件下成功制备了WPI和低聚木糖的美拉德反应产物 (MRPs)。数据显示,质量比为1:2的溶液体系美拉德反应程度最高;与未经过美拉德反应的体系相比,MRPs的平均粒径均减小而质量比为1:2的体系平均粒径最大;同时,美拉德反应提高了WPI的乳化活性和乳化稳定性,比例为1:2时MRPs具有最佳的乳化活性(38.63 m2/g)和乳化稳定性(65.23%);流变学测试表明糖基化修饰增强了WPI的凝胶性,比例为1:3时MRPs的储存模量提高最大,G''值高达约97,000 Pa (约WPI的7倍);在相同剪切速率下,MRPs溶液的表观粘度增加,而WPI的添加比例对体系粘度的影响占主导作用。上述研究表明,美拉德反应可改善WPI的乳化特性和凝胶特性。     

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。     

酶解对鸡骨素美拉德反应挥发性风味成分的影响

为了探索酶解对鸡骨素美拉德反应香精挥发性风味成分的影响,采用固相微萃取/气相色谱-嗅闻-质谱(SPME/GC-O-MS)技术对清汤型和白汤型鸡骨素美拉德反应产物(清汤MRPs1和白汤MRPs1)及鸡骨素酶解液美拉德反应产物(清汤MRPs2和白汤MRPs2)中的挥发性风味成分进行比较分析。在4种产物中共鉴定出 70种挥发性化学成分,清汤MRPs1中29种,MRPs2中50种;白汤MRPs1中38种,MRPs2中53种。与 MRPs1 相比,MRPs2 中醛酮、杂环类化合物的浓度显著增加(p<0.05)。白汤MRPs2的醛酮类物质种类更多,反-2-壬烯醛、2-十一碳烯醛、反-2-癸烯醛、反,反-2,4-癸二烯醛、3-羟基-2-甲基-4-吡喃酮、6-甲基-5-庚烯-2-酮等特征香气成分只在白汤骨素中检出。但是在清汤MRPs2中杂环类物质则更加丰富,例如2-乙酰基呋喃、2,5-二甲基-3-乙基吡嗪、3,5-二甲基-2-乙基吡嗪、2-甲基-3,5-二乙基吡嗪、3,6-二甲基-2-异戊基吡嗪等则只在清汤骨素中检出。酶解对鸡骨素美拉德反应产物中的挥发性风味成分的种类和浓度有相当大的影响,增加了终产物的烤香、脂香和肉香,使整体风味更加浓厚饱满。     

美拉德反应改性壳聚糖产物体外抗氧化能力的研究

利用美拉德反应对壳聚糖进行改性来提高其抗氧化能力。通过测定改性后壳聚糖美拉德反应产物(MRPs)的DPPH自由基清除率、还原能力及螯合铁离子能力,确定不同壳聚糖粘度及浓度、葡萄糖浓度、pH和温度的反应条件对MRPs体外抗氧化能力的影响。结果表明,壳聚糖经改性后,MRPs体外抗氧化能力得到显著改善(p<0.05)。MRPs的DPPH自由基清除率、还原能力与葡萄糖浓度、壳聚糖浓度和温度呈现正相关趋势。低、中粘度壳聚糖MRPs仅在还原能力上有显著差异(p<0.05)。1%的低、中粘度壳聚糖改性后MRPs铁离子螯合率比改性前分别提高了34.41%、24.5%。pH在3.6～5.4内对壳聚糖MRPs体外抗氧化能力有比较复杂的影响。      

Increase in antioxidant effect of ginsenoside Re-alanine mixture by Maillard reaction

Ginsenoside Re, one of the major triol type ginsenosides contained in Panax ginseng, has a hydrophobic four-ring steroid-like structure with hydrophilic sugar moieties at carbon-3 and -20. The aim of the present study was to identify the changes in structure and antioxidant activity of ginsenoside Re by the Maillard reaction, which has not been reported yet. The free radical-scavenging activity of ginsenoside Re-alanine mixture was increased by heat-processing. Ginsenoside Re was gradually changed into Rg₂, Rg₆ and F₄ by heat-processing, and the glucosyl moiety at carbon-20 was separated. The improved-free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant Maillard reaction products (MRPs). Antioxidant MRPs were generated from the reaction of glucose and alanine. Based on the viability results of LLC-PK1 renal epithelial cells, MRPs and less-polar ginsenosides contributed to the combined renoprotective effect against oxidative renal damage. Maillard reaction is importantly involved in the increased antioxidant effect of ginsenoside by heat-processing.     

Effect of xylose on the molecular and particle size distribution of peanut hydrolysate in Maillard reaction system

BACKGROUND: The Maillard reaction is a complex series of reactions between reducing sugars and amino groups. Changing any of reaction parameters would alter the reaction pathway. This study investigated the effect of xylose concentration on the molecular and particle size distribution of Maillard reaction products (MRPs) derived from peanut hydrolysate and xylose to discuss their formation mechanism. RESULTS: Molecular weight and particle size distribution analyses indicated that both peptide degradation and peptide cross‐linking occurred during the Maillard reaction. Heat treatment would make the high‐molecular‐weight peptides degrade into low‐molecular‐weight peptides and free amino acids. Maillard reaction increased the molecular weight and particle sizes of products as the xylose concentration increased from 1% to 4%. CONCLUSION: The study shows that both peptide degradation and peptide cross‐linking occurred during the Maillard reaction. The thermal degradation product (TDP) and MRPs had significantly different molecular size distribution, and the particle size distribution of TDPs and MRPs had similar change tendency to that of the molecular size distribution. These would provide an insight into the formation mechanism of MRPs. Copyright © 2011 Society of Chemical Industry