Antioxidant activity,polyphenols, caffeine and melanoidins in soluble coffee: The influence of processing conditions and raw material

The production of soluble coffee starts with the selection of beans and is followed by roasting, grinding, extraction and drying. Lyophilised soluble coffees extracted by various methods from light, medium and dark-roasted arabica and robusta beans were evaluated for antioxidant activity (AA) using ABTS, Folin, DPPH and FRAP techniques. Caffeine, chlorogenic acid (5-CQA) and melanoidin content was also quantified. The data were analysed by principal component analysis. The AA values derived from the various methods used were correlated. Roasting resulted in the degradation of 5-CQA and formation of melanoidins, while AA was largely unaffected by roasting. The extraction of soluble coffee more prominently affected the AA of light-roasted coffee, mainly because it favoured the extraction of 5-CQA. The larger caffeine content in robusta coffee resulted in greater AA. All of soluble coffee products studied possessed antioxidant potential, which was conferred by their concentrations of phenolic compounds, caffeine and melanoidins.     

Isolation and characterisation of a coffee melanoidin fraction

BACKGROUND: Melanoidins contribute to the colour and flavour of coffee brews and are also reported to be physiologically active components. However, structural information about coffee melanoidins is rare and current models are supported by few data. RESULTS: Using hydrophobic interaction chromatography (HIC), melanoidin fractions were isolated from different high‐molecular‐weight fractions of coffee brews obtained by ultrafiltration. Generally, melanoidin fractions isolated by HIC showed three‐ to fourfold higher antioxidant activities than the remaining high‐molecular‐weight material in the ultrafiltration fractions. Melanoidin fractions showed an intense brown colour: aqueous solutions with a concentration as low as 40 µg mL^?1 were distinguishable from pure water. The melanoidin fractions contained less than 6% each of releasable carbohydrates and amino acids. The molecular masses of the melanoidins were estimated to be between 3 and 22 kDa, irrespective of the ultrafiltration fraction from which they were obtained. Two‐dimensional nuclear magnetic resonance studies revealed an enrichment of phenolic/aromatic/olefinic structural units and did not support the idea of intact ferulate or caffeate moieties integrated into the melanoidin polymer. CONCLUSION: These studies support melanoidin models describing them as high‐molecular‐weight compounds themselves as opposed to models describing them as low‐molecular‐weight chromophores bound to polysaccharides or proteins. Phenolic constituents are more likely integrated into melanoidins as condensed phenolics than as intact hydroxycinnamates from chlorogenic acids. Copyright © 2008 Society of Chemical Industry     

小磨香油芝麻渣中类黑精的提取及抗氧化活性分析

以小磨香油芝麻渣为原料,利用不同溶液辅助超声提取芝麻渣中的类黑精,并采用电子舌对类黑精的滋味进行检测、傅里叶红外对其结构进行初步分析、及类黑精抗氧化活性的检测和分析。结果表明,以p H 10.0碱溶液为提取液中的类黑精含量最高,其次是60%乙醇溶液,且醇提类黑精有更强的苦味;p H 10.0碱提组分的蛋白含量最高,60%醇提组分的总糖含量最高,分别为47.58%和25.18%,芝麻渣类黑精主要是蛋白结合型;芝麻渣类黑精最突出的滋味是苦味,最高苦味值达到7.28±0.03,其次是鲜味;随着类黑精浓度的增加,几种抗氧化活性指标有增加的趋势,其中用水提取的有最好的·OH清除效果,达到56.52%,60%醇提类黑精在浓度为1 mg/mL时,DPPH·清除率已高达95%;芝麻渣类黑精中具有芳族胺和呋喃等杂芳环结构。本研究说明芝麻渣类黑精适合用p H10碱溶液和60%醇溶液提取且具有较好的抗氧化活性,为芝麻渣类黑精的初步探索以及芝麻渣的开发利用提供了一定理论依据。     

Metabolomic approach for understanding phenolic compounds and melanoidin roles on antioxidant activity of Indonesia robusta and arabica coffee extracts

Our experiments investigated roles of phenolic compounds and melanoidins on antioxidant activity of Indonesia robusta and arabica coffee extracts. The 2,2,-diphenyl-1-picrylhydrazyl (DPPH) assay and a ferric reducing antioxidant power (FRAP) method were used to determine the antioxidant activity. An increase in the roasting degree (green, light, medium, and dark) reduced phenolic compounds and the antioxidant activity of coffee extracts, but enhanced melanoidin content. Principle component analysis (PCA) demonstrated that phenolic compounds showed stronger effects on antioxidant activity of coffee extracts in comparison with melanoidins. This finding was supported by the results of metabolomic fingerprint by partial least square (PLS), which describes the correlation of functional groups of coffee extracts on antioxidant activity. Based on the PLS analysis, hydroxyl groups (O–H) were observed to show a positive correlation, but carbonyl (C=O) and amine (N–H) groups were attributed to a negative correlation on antioxidant activity of coffee extracts.     

Peroxyl radical scavenging activity of melanoidins in aqueous systems

Melanoidins are widely distributed in our diet, due to home or industrial processing of foods. Until recently, melanoidins were considered to be an inert, brown-coloured polymeric component. However, recent research into their nutritional, physiological, and functional properties has suggested that they have antioxidant properties, and we address this issue in this work. A sensitive procedure for assessing the inhibition of lipid peroxidation by melanoidins in watery media has been developed. Main drawbacks and critical steps of the procedure are discussed. Melanoidins can be classified according to the number of peroxyl radicals trapped per molecule. Coffee and sweet wine melanoidins show higher antioxidant activity than melanoidins isolated from beer. For the first time, a linear relationship between the peroxyl radical scavenging activity and the chromophore residues in the melanoidin skeleton responsible for browning has been established.     

云南小粒咖啡类黑精的抗氧化及减肥功能

目的：探讨云南小粒咖啡类黑精的抗氧化能力和减肥功能。方法：用热水提取法提取中烘焙度云南小粒咖啡中的类黑精（M总）,再将提取的类黑精产物按分子质量大小分成＞100 kDa（M1）、10～100 kDa（M2）、＜10 kDa（M3）3 个部分。用羟自由基、1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除率和总还原力评价M总、M1、M2、M3的抗氧化能力;通过饲喂高脂饲料建立大鼠肥胖模型,检测不同质量浓度咖啡类黑精对肥胖大鼠体质量、体脂质量、血脂水平、脂体比、脂肪组织形态、肝脏组织形态等指标的影响。结果：相同质量浓度下,云南小粒咖啡类黑精不同分子质量产物自由基清除能力和总还原力不同;不同剂量处理组咖啡类黑精均能降低大鼠体质量、体脂质量;肝组织切片显示,中、高剂量处理组大鼠肝脏组织结构完整、肝细胞大小一致、胞浆均匀、细胞核清晰;脂肪组织切片显示,高剂量处理组大鼠脂肪细胞较模型组减小,且排列均匀、结构完整。结论：云南小粒咖啡类黑精及不同分子质量产物均具有不同程度抗氧化能力;高质量浓度（72 g/100 mL）云南小粒咖啡类黑精具有一定的减肥作用,能抑制大鼠体质量的增加,减少肝脏内脂肪堆积,对肝脏具有一定的保护作用。     

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

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.     

黑酱油类黑素的提取、光谱性质及功能

从黑酱油中提取类黑素并对其光谱性质和功能进行研究。结果表明：经有机溶剂沉淀及脱盐处理,冷冻干燥获得类黑素粗制品,得率为22.8g/100mL;经Sephadex G-50凝胶层析除去小分子物质,得到分子质量分布在3000～55000u的类黑素纯品。紫外和红外光谱扫描结果显示类黑素粗品是美拉德反应和酶促褐变的产物。类黑素粗制品对DPPH自由基的清除率最高达89.0%,对羟自由基的清除能力达89.5%,对亚硝胺合成的抑制率可达80.0%。提示酱油类黑素粗制品可以作为功能性固体酱油被开发,类黑色素纯品可开发成为功能性食用色素。     

Honey melanoidins: Analysis of the compositions of the high molecular weight melanoidins exhibiting radical-scavenging activity

Size-exclusion chromatography (SEC) and activity-guided fractionation of honeys allowed the isolation of high molecular weight brown compounds, ranging in size from 66 to 235 kDa that exhibited peroxyl radical-scavenging activity. Their concentrations, antioxidant activity and degree of browning increased after heat-treatment of honeys, suggesting that they represent melanoidins. Chemical analysis of melanoidins demonstrated the presence of proteins, polyphenols and oligosaccharides. Heat-treatment caused an increased incorporation of phenolics into high molecular weight melanoidins and drastically decreased the protein content in these fractions with a concomitant appearance of high molecular weight protein–polyphenol complexes of reduced solubility. LC–ESI–MS demonstrated the presence of oligosaccharide moieties, supporting the postulated origin of melanoidins. The changes in the phenolic content of melanoidins from heated honeys were strongly correlated with their oxygen radical absorbance capacity (ORAC) values (R = 0.75, p < 0.0001), indicating that polyphenols contribute to the antioxidant activity of melanoidins. In summary, honey melanoidins are multi-component polymers consisting of protein–polyphenol–oligosaccharide complexes. A direct interaction between polyphenols and melanoidins resulted in a loss or gain of function for melanoidin antioxidant activity.     

Ethanol in food: liquid–vapour partition in model systems containing Maillard reaction products

The effect of Maillard reaction products (MRPs) with different browning degree on the liquid–vapour partition of ethanol was studied in model systems. In particular, glucose–glycine aqueous solutions subjected to different heat treatments, which consequentely had different water activity values, were added to increasing amounts of ethanol and analysed for ethanol vapour pressure. In order to study the effects of the water activity change and of melanoidins' formation on the ethanol partition, experiments were also carried out on samples equilibrated at the same water activity. Ethanol vapour pressure decreased as the Maillard reaction proceeded. This result was attributed to the increase in water activity rather than to binding effects of melanoidins towards ethanol. Changes in water activity were mainly due to reagent consumption, water molecule formation and melanoidin production.     

Espresso coffee (EC) by POD: Study of thermal profile during extraction process and influence of water temperature on chemical–physical and sensorial properties

In this work the thermal profiles of five coffee pods (pure Arabica, pure Robusta, and Arabica Robusta blends: A20R80, A80R20, and A40R60) at 90, 100 and 110 °C are reported. Moreover the chemical–physical and sensorial properties of espresso coffee (EC) obtained from five different coffee pods were investigated. The analysis of the thermal profiles highlighted that the extraction process can be considered as an isothermal process because, after a starting phase, the recorded temperatures stayed around a mean temperature (T_m). In addition the T_m recorded for each extraction temperature was significantly lower than those set up by the controller. The chemical–physical parameters of EC samples increased proportionally with extraction temperature highlighting that the effectiveness of extraction process scales up with percolation temperature. The solid and caffeine contents of the EC samples extracted at 110 °C are related to an over extraction process. Principal Component Analysis (PCA) was applied to identify relationships and differences among EC samples. Pure Arabica and A80R20 EC samples at 100 and 110 °C have shown sensorial attributes typical for a fine espresso coffee.     

How Does Roasting Process Influence the Retention of Coffee Aroma Compounds by Lyophilized Coffee Extract?

ABSTRACT:  The aims of this study were (1) to study the effect of lyophilized coffee extract on the retention of aroma compounds and (2) to study if aroma compounds selected are differently affected by the lyophilized coffee extracts obtained from conventional and Torrefacto coffee brews prepared by filter coffeemaker and by espresso coffee machine. Variable amounts of lyophilized coffee extracts, relative to coffee powder, containing different percentages of high molecular weight compounds, mainly melanoidins (value given in parentheses), were obtained: 20.9% (14.8) and 24.9% (23.3), respectively, for conventional and Torrefacto coffee brew prepared by filter coffeemaker and 18.1% (18.8) and 20.7% (57.5), respectively, for conventional and Torrefacto coffee brew prepared by espresso coffee machine. The retention of aroma compounds increased by increasing the lyophilized coffee extract concentration and was found to be dependent on the aroma compounds. The retention of aroma compounds was found to be slightly different depending on the brewing procedure employed, showing lyophilized coffee extracts obtained with espresso coffee machine had higher retention values that those extracted by filter coffeemaker. Retention capacity of lyophilized coffee extracts obtained from the conventional and the Torrefacto roasted coffee did not show differences except in the case of ethyl nonanoate.     

Phytochemical and microbiological stability of spent espresso coffee grounds in capsules

Wet spent coffee grounds (SCGs) from espresso capsules, a post-consumer organic solid residue produced worldwide, were analysed to determine their chemical and microbiological stability during storage. In particular, the changes in the total phenolic content and antioxidant capacity (based on two free radical scavenging assays and one oxygen radical absorbance assay) were determined on espresso SCG stored in capsules for up to one month at room temperature in a container open to the air. Phenolic compounds were also identified and quantified using high performance liquid chromatography coupled with diode array and mass detectors. Microbiological analysis was performed in parallel on the same stored SCG to determine the total counts and quantify the main microbial groups present during the storage. The total phenolic content, antioxidant capacity and the most important bioactive compounds, such as the total caffeoylquinic acids, were significantly stable during storage for up to one month, while overall microbial stability was observed for up to two weeks of storage. Overall, the recovery of espresso coffee capsules within 15 days could guarantee the maintenance of microbiological stability as well as the content of valuable antioxidant compounds.     

A neuro‐fuzzy computational approach for multicriteria optimisation of the quality of espresso coffee by pod based on the extraction time,temperature and blend

We demonstrate how soft computing methods can be exploited to solve multicriteria quality optimisation problems in food science and technology. In particular, we link neuro‐fuzzy modelling techniques with simulated annealing to optimise/design the quality of espresso coffee by pod. The design variables are the extraction time (ranging from 10 to 30 s), temperature (80–110 °C) and blends (100% Arabica, 100% Robusta and Arabica Robusta: A20R80, A80R20 and A40R60); they are not the only variables that affect the sensory profile of a cup of espresso coffee, but have a strong impact on the sensory quality of the beverage. Based on the framework, we show that the particular problem is a nonlinear one. Hence, an espresso coffee characterised by a specific sensory profile can be extracted using different sets of parameter values. For example, the same sensory profile can be obtained using either pure Robusta extracted at 22 s and 94 °C or 90% Arabica and 10% Robusta extracted at 25 s and 99 °C. Yet, the global optimum with respect to the distance to the optimum sensorial values is obtained using 70% Arabica and 30% Robusta extracted at 15 s around 93 °C.     

The recognition of high molecular weight melanoidins as the main components responsible for radical-scavenging capacity of unheated and heat-treated Canadian honeys

As the Maillard reaction is known to occur in heat-treated foods, unheated and heated honey samples were subjected to the activity-guided fractionation and size-exclusion chromatography to compare the degree of browning, radical scavenging activity (ORAC) and molecular size of the fractions obtained. Heat-treatment increased browning in the fractions of light- and medium-coloured honeys (p < 0.002), accelerated the formation of high molecular weight melanoidins (85–232 kDa) and significantly increased ORAC values (p < 0.0001). In contrast, melanoidin content and ORAC decreased in the fractions of heat-treated dark buckwheat honey (p < 0.001). Unheated dark honey contained a significantly higher amount of melanoidins than other honeys (p < 0.007). Together, results showed that at low initial concentration of melanoidins, heat-treatment accelerated formation of new melanoidins and increased ORAC, while at high concentration it caused decrease and a reduction of radical scavenging activity. This study emphasises the importance of non-enzymatic browning in the prediction of the antioxidant pool in thermally processed honeys.     

Iron-binding ability of melanoidins from food and model systems

Soluble high molecular weight fractions isolated from the development of the Maillard reaction in 22 different model systems and food matrices were studied in order to assess their iron-chelating ability in vitro. Melanoidins and iron were incubated in a Na-acetate buffer (0.1 M, pH 5) at different weight ratios and free iron was measured by FAAS and the bathophenantroline procedure at the steady state. Melanoidins were classified at three levels according to their number of co-ordination sites for iron. Melanoidins from coffee (medium roasted), different types of beer (Pilsener, Abbeys, and dry-stout styles), and sweet wine (Pedro Ximenez) exerted a low iron-binding effect compared with melanoidins from model systems. The type of sugar was shown to be a significant parameter for obtaining melanoidins with high iron ability, and glucose was more efficient than lactose. No relationship was observed between browning and iron binding ability of melanoidins from model systems. The chromophoric residues were not the main co-ordination sites for iron complexation in the melanoidin structure.     

Sensory profile of Italian Espresso brewed Arabica Specialty Coffee under three roasting profiles with chemical and safety insight on roasted beans

Specialty coffee (SC) has been showing an increasing interest from the consumers which appreciate its traceability and the peculiar flavours from each single origin. Additionally, the processes to which coffee fruits underwent to get green coffee characterise the beans in terms of macromolecules acting as substrates during the roasting. This work evaluates via sensory analysed eight SC, roasted at light, medium, and dark level, submitted to Italian espresso extraction, to assess how different roasting levels exalt the expected cup profile obtained by the suppliers via cupping in origin countries. Finally, roasted beans were characterised for physico-chemical features (pH, titratable acidity, caffeine, melanoidins, polyphenols and acrylamide). Sensory analysis demonstrated that the intermediate roasting level and espresso extraction match better attributes from in-origin cupping. Melanoidins (mmol g⁻¹ coffee d.b.) was able to discriminate among roasting levels (light 0.12 ± 0.01; medium 0.13 ± 0.003; dark 0.14 ± 0.01; α = 0.05). Acrylamide analyses ensured compliance with the food safety standards (light 301.9 ± 37.2 ppb; medium 126.1±19ppb; dark 107.9 ± 22.5ppb). Physico-chemical features were able to cluster samples from different origins within the same roasting level (α = 0.05). Results showed correlations (α = 0.01) between sensory analysis and physico-chemical values: direct for caffeine and astringency, reverse for perceived acidity in relation to astringency, roasted, dried fruits and nutty notes.     

Effect of coffee melanoidin on human hepatoma HepG2 cells. Protection against oxidative stress induced by tert-butylhydroperoxide

Soluble high-molecular weight fraction (named melanoidin) from coffee brew was isolated by ultrafiltration, subsequently digested by simulating a gastric plus pancreatic digestive condition and partly characterized by CZE, gel-filtration and browning. The objective of the present study was to investigate the potential protective effect of the coffee melanoidin submitted to gastrointestinal digestion on cell viability (lactate dehydrogenase leakage) and redox status of cultured human hepatoma HepG2 cells submitted to oxidative stress induced by tert-butylhydroperoxide (t-BOOH). Concentration of reduced glutathione (GSH) and malondialdehyde (MDA), generation of reactive oxygen species (ROS) and activity of antioxidant enzymes glutathione peroxidase (GPx) and reductase (GR) were used as markers of cellular oxidative status. Pretreatment of cultured HepG2 cells with 0.5-10 microg/mL digested coffee melanoidin (DCM) for 2 or 20 h completely prevented the increase in cell damage and GR and partly prevented the decrease of GSH and the increase of MDA and GPx evoked by t-BOOH in HepG2 cells. In contrast, increased ROS generation induced by t-BOOH was not prevented when cells were pretreated with DCM. The results show that treatment of HepG2 cells with concentrations of DCM within the expected physiological range confers the cells a significant protection against an oxidative insult.     

Comparison of nine common coffee extraction methods: instrumental and sensory analysis

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids ? texture/body, headspace intensity ? aroma intensity, concentrations of caffeine/chlorogenic acids ? bitterness and astringency.     

Optimization of espresso machine parameters through the analysis of coffee odorants by HS-SPME-GC/MS

The aroma profile and the final quality of espresso coffee (EC) are influenced by such technical conditions as the EC machine extraction temperature and the pressure used. The effect of these two parameters on EC quality were studied in combination by headspace solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS) and sensory profile. Moreover, 10 key odorants at the best EC machine settings were examined to compare the two coffee cultivars (Arabica and Robusta) and two EC machines [Aurelia Competizione (A) and Leva Arduino (B)]. The data obtained provides important information about espresso making technique, suggesting that the usual espresso machine temperature and pressure settings (i.e. 92°C and 9bar) are very close to those needed to obtain the best quality espresso. This confirms the traditional wisdom of coffee making, which judges 25ml, the typical volume of a certified Italian EC, to be ideal for very strong aroma intensity.