Roasting process affects differently the bioactive compounds and the antioxidant activity of arabica and robusta coffees

The influence of different roasting degrees on the content of bioactive compounds and the antioxidant activity (AA) of arabica and robusta coffees was evaluated. AA was estimated by Folin–Ciocalteau, FRAP and ABTS methods. The results were analyzed by principal components analysis. While the levels of 5-CQA (5-caffeoylquinic acid), trigonelline, furfural and HMF (hydroxymethylfurfural) decreased with the degree of roasting, the level of melanoidins increased. Changes in the levels of the bioactive compounds were more intense that those observed for AA. PC 1 (principal component 1) was mainly correlated with the levels of, furfural, HMF, 5-CQA, trigonelline, and melanoidins. PC2 was mainly correlated with AA and caffeine content. Different compounds contribute to the AA of the coffee and the final result for AA is dependent on the balance of the compounds formed and degraded during the roasting process.     

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting

The bioactive composition of coffee, as one of the most popular beverages in the world, has attracted interest as a potential source of beneficial bioactive compounds, especially polyphenols and caffeine. Since the content of these compounds is affected by the processing conditions, the objective of this study was to determine the content of polyphenolic compounds and caffeine in four different coffee varieties: Minas and Cioccolatato (Coffea arabica), and Cherry and Vietnam (Coffea canephora syn. Coffea robusta), roasted by three varying degrees (light, medium and dark). The content of the polyphenolic compounds and the antioxidant capacity of coffees were determined using UV/Vis spectrophotometric methods, while the content of chlorogenic acid derivatives was determined using HPLC analysis. The caffeine content was determined by means of two spectrophotometric methods, as well as HPLC analysis. Additionally, raw caffeine was also obtained by an isolation procedure with chloroform. Cherry coffee, a variety of C. canephora exhibited the highest overall content of total phenols (42.37 mg GAE/g), followed by Minas coffee, while Cioccolatato contained the lowest TPC (33.12 mg GAE/g). Cherry coffee also exhibited the highest content of individual classes of polyphenols (flavan-3-ols, procyanidins and tannins), while the highest content of chlorogenic acid (CQA) derivatives was determined in Minas and Cioccolatato coffees (C. arabica). The highest content of total and individual polyphenolic compounds was determined in coffees roasted in both light and medium roasting conditions, which was also observed for the content of CQA derivatives and antioxidant capacity of roasted coffees. The highest caffeine content in the coffee samples was determined by employing the HPLC analysis (0.06–2.55%). Light roasted Cherry coffee contained the highest overall content of caffeine among all coffees, which exhibited a decrease with intensified roasting.     

Physicochemical characteristics of Ethiopian Coffea arabica cv. Heirloom coffee extracts with various roasting conditions

This study aimed to investigate the physicochemical characteristics of Ethiopian Coffea arabica cv. Heirloom coffee extracts with various roasting conditions. Green coffee beans were roasted at four different conditions (Light-medium, Medium, Moderately dark, and Very dark) and used to extract espresso and drip coffee. Moisture content in coffee beans was decreased as the roasting degree increased. The contents of crude fat and ash were lower in the Light-medium roasted coffee beans than in green coffee beans but increased as the roasting degree increased. The values of lightness (L^*), redness (a^*), yellowness (b^*), and browning index of coffee extracts were decreased as the roasting degree increased. Total dissolved solids in espresso coffee were increased with increasing roasting degree but decreased in drip coffee. In both the extracts, the contents of reducing sugar, titratable acidity, organic acids, and chlorogenic acid were decreased, but that of caffeine was increased with the roasting degree increased.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-020-00865-w.     

Evaluation of sensory attributes of coffee brews from robusta coffee roasted under different conditions

Robusta coffee beans with a different initial moisture of 5, 7.5 and 10% were convectively roasted at 230 °C, microwaved at 700 W, and roasted by the coupled convective-microwave method. Sensory attributes of brews prepared from these coffee samples were evaluated. Final temperature of microwaved coffee beans was lower than that of the beans processed by the two other methods, which resulted in a higher content of volatile aroma compounds and a lesser degree of charring of their surface. Lower initial humidity of coffee beans shortened the time of roasting. However, the aroma developed upon roasting of the moistest beans was the most intense and pleasant. Modification of roasting conditions increased shifting of the overall acceptability of coffee infusions by 2 points in a 10-point hedonic scale, which implies that, if roasting conditions are adequate to the type of coffee, its sensory characteristics can be improved. Thus, optimization of roasting parameters can increase the share of robusta in well-accepted commercial coffee blends, a convenient fact because of the significant difference in price between the latter and arabica coffee.     

Structure expansion of green coffee beans using instantaneous controlled pressure drop process

Since 1988, when the first experiments with the Instantaneous Controlled Pressure Drop (DIC) process were performed, a lot of investigations have been carried out concerning the structure expansion, processing kinetics (drying, extraction and sterilization) and the improvement of the functional and organoleptic properties of fresh and dried foods. In this study, two DIC technologies were used to expand the structure of green coffee beans. Two varieties of commercial Arabica coffee beans of different agricultural and geographical origins (Brazilian and Ethiopian) were inspected. The effect of initial moisture content (7–40% dry basis), type of heating in the DIC process (steam and microwaves), processing parameters like pressure (0.4–0.7 MPa) and heating time (20–200 s) on bean expansion were investigated. The expansion was evaluated as the ratio of the tapped density of raw beans to that of the treated material. The hydration capacity of the beans was also studied. The Response Surface Methodology was employed to optimize the processing parameters. After the steam DIC treatment, the maximum expansion ratio of the Brazilian beans (e = 1.74) was higher than that of the Ethiopian beans (e = 1.59). For Brazilian beans, the steam DIC treatment resulted in a higher value of expansion ratio than the MW DIC treatment (e = 1.39). Concerning hydration capacity, the steam DIC treatment gave values of 78.6% and 48.2% d.b. for the Ethiopian and Brazilian beans, respectively. It means almost two-fold increase in the hydration capacity using DIC treatment. The steam DIC treatment increased and accelerated in twice the weight loss of beans during roasting.

Industrial relevance

Preliminary experiments have shown that the structure expansion of green coffee beans significantly reduced the roasting time, amended the bean suitability to grinding and improved the kinetics and yield of caffeine and active compounds extraction. The industrial DIC processes can be distinguished by high quality of final products, energy saving and positive environmental impact. Due to the fragile structure of coffee beans, a batch process should be applied. Industrial plant can be designed as a tower plant with several compartments separated by guillotine valves where the material falls down by gravity force or a carrousel or a linear plant with filling, DIC treatment and discharging operations. The ABCAR DIC Process Company (La Rochelle, France) develops plants with a capacity of 50 kg/h to 8 ton/h of dry coffee beans. Despite the promising experimental results concerning microwave DIC technology, the industrial applications are so far limited to the steam DIC treatment due to technical reasons.     

云南不同地区烘焙咖啡豆主要成分分析及类黑精组成成分

以云南3个咖啡主产区(普洱、怒江、德宏)的生咖啡豆为原料,通过不同程度(轻度、中度、重度)烘焙,对其主要成分进行分析,并提取类黑精,采用热裂解-气相色谱-质谱(pyrolysis-gas chromatography-mass spectrometry,Py-GC-MS)联用技术分析咖啡类黑精的化学组成。结果显示:随着烘焙程度加深,咖啡豆的蛋白质和粗脂肪含量增加,总氨基酸含量降低,其中蛋白质含量最高为重度烘焙后的普洱咖啡豆(16.3 g/100 g),氨基酸含量最高为普洱生咖啡豆(9.41%),粗脂肪含量最高为中度烘焙后的德宏咖啡豆(13.85 g/100 g),矿物质元素中含量较高的为K、Mg、P、Ca,普洱咖啡豆经重度烘焙后K含量最高(2.2 g/100 g)。Py-GC-MS分析结果表明:不同产地、不同烘焙程度咖啡豆的类黑精组成差异明显,但也存在共性特征,咖啡因和酸类相对含量最高,其次是胺类、酯类、酚类、吡咯类、呋喃类、吡啶类、醛类、醇类、酮类等。     

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.     

Effect of the roasting method on the content of 5-hydroxytryptamides of carboxylic acids in roasted coffee beans

Coffee beans of Coffea liberica (robusta) variety were roasted using convection and microwave heating. For roasting we used green coffee beans of 7.5% moisture content, and beans wetted to 10% moisture content and dried to 5% moisture content. The content of 5-hydroxytryptamides of carboxylic acids C-5-HT (determined by TLC) as the index of substances irritating alimentary canal was investigated in the roasted beans, depending on the bean treatment before roasting and applied roasting method. Analytical results show that predrying of the coffee beans caused 15-30% loss of C-5-HT, depending on the applied drying conditions. The content of C-5-HT in the roasted beans depended on the roasting method and preliminary treatment of the beans prior to roasting. A higher C-5-HT loss occurred in the case of beans subjected to two-stage processing, predrying and roasting. Convection roasting caused higher degradation of C-5-HT than microwave roasting.     

Bioactive composition and antioxidant potential of different commonly consumed coffee brews affected by their preparation technique and milk addition

Coffee is one of the most popular beverages in the world, prepared and consumed in many different ways. Taste, aroma and composition of the coffee brew vary depending on the preparation method. Therefore, this study investigates the effect of different brewing methods on the polyphenol and methylxanthine composition and antioxidant capacity of thirteen different coffee brews. The content of total phenols and flavonoids was determined spectrophotometrically and the content of chlorogenic acid derivates (3-CQA, 4-CQA and 5-CQA) and caffeine using the high performance liquid chromatography (HPLC-PDA). Antioxidant capacity of coffee brews was evaluated by using the ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) and FRAP (ferric-reducing antioxidant power) assays. Instant coffee brews showed the highest values in content of total phenols, chlorogenic acid derivates, caffeine and antioxidant capacity, which significantly decreased by milk addition. The antioxidant capacity of coffee brews was in compliance with the total phenol content and content of chlorogenic acid derivates.     

Effect of the roasting method on the content of 5‐hydroxytryptamides of carboxylic acids in roasted coffee beans

Coffee beans of Coffea liberica (robusta) variety were roasted using convection and microwave heating. For roasting we used green coffee beans of 7.5% moisture content, and beans wetted to 10% moisture content and dried to 5% moisture content. The content of 5‐hydroxytryptamides of carboxylic acids C‐5‐HT (determined by TLC) as the index of substances irritating alimentary canal was investigated in the roasted beans, depending on the bean treatment before roasting and applied roasting method. Analytical results show that predrying of the coffee beans caused 15–30% loss of C‐5‐HT, depending on the applied drying conditions. The content of C‐5‐HT in the roasted beans depended on the roasting method and preliminary treatment of the beans prior to roasting. A higher C‐5‐HT loss occurred in the case of beans subjected to two‐stage processing, predrying and roasting. Convection roasting caused higher degradation of C‐5‐HT than microwave roasting.     

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.     

Use of a 5-caffeoylquinic Acid/Caffeine Ratio to Monitor the Coffee Roasting Process

The extent of alteration in the chemical composition of coffee beans roasted to develop the flavor and aroma associated with coffee beverage was reliably monitored by observing the decomposition of naturally occurring 5-caffeoylquinic acid (5-CQA) and ratioing this concentration to that of the relatively heat stable caffeine. An HPLC method was developed by which simultaneous quantification of 5-CQA and caffeine could be used to monitor degree of roast.     

咖啡精油超临界CO2萃取工艺优化及理化特性分析

以云南保山小粒咖啡豆为对象,根据国家标准,测定生、熟咖啡豆的营养成分,在单因素实验的基础上,以响应面优化超临界CO₂萃取咖啡精油的工艺参数;测定生、熟咖啡精油理化指标,并通过气相色谱-氢火焰离子化检测器（GC-FID）分析生、熟咖啡精油的脂肪酸组成。结果表明:经烘焙处理后,熟咖啡豆中水分、水浸出物、咖啡因、总糖、粗纤维和粗脂肪含量与生咖啡豆中的存在显著差异（P<0.05）;超临界CO₂萃取生咖啡精油的最佳工艺条件为萃取压力25 MPa,萃取温度54 ℃,萃取时间150 min,在此条件下咖啡精油萃取得率为13.98%。烘焙处理前后,咖啡精油各常规理化指标无显著差异,且均符合国家标准要求。通过GC-FID分别检测到15和16种脂肪酸,其中亚油酸、棕榈酸、硬脂酸和油酸等为主要脂肪酸,烘焙对咖啡豆脂肪酸组成影响不明显,但各脂肪酸的含量存在一定差异。烘焙对咖啡豆及咖啡精油的各项指标均有一定程度的影响,为云南地区咖啡产业发展提供科学依据。     

Espresso coffees, caffeine and chlorogenic acid intake: potential health implications

HPLC analysis of 20 commercial espresso coffees revealed 6-fold differences in caffeine levels, a 17-fold range of caffeoylquinic acid contents, and 4-fold differences in the caffeoylquinic acid?:?caffeine ratio. These variations reflect differences in batch-to-batch bean composition, possible blending of arabica with robusta beans, as well as roasting and grinding procedures, but the predominant factor is likely to be the amount of beans used in the coffee-making/barista processes. The most caffeine in a single espresso was 322 mg and a further three contained >200 mg, exceeding the 200 mg day(-1) upper limit recommended during pregnancy by the UK Food Standards Agency. This snap-shot of high-street expresso coffees suggests the published assumption that a cup of strong coffee contains 50 mg caffeine may be misleading. Consumers at risk of toxicity, including pregnant women, children and those with liver disease, may unknowingly ingest excessive caffeine from a single cup of espresso coffee. As many coffee houses prepare larger volume coffees, such as Latte and Cappuccino, by dilution of a single or double shot of expresso, further study on these products is warranted. New data are needed to provide informative labelling, with attention to bean variety, preparation, and barista methods.     

Species,roasting degree and decaffeination influence the antibacterial activity of coffee against Streptococcus mutans

Coffee beverage has been associated with antibacterial activity against Streptococcus mutans, a cariogenic bacterium. This study aimed at identifying natural compounds in coffee that contribute to such activity and investigate the influence of species, roasting and decaffeination on it. Coffee chemical compounds and aqueous extracts of green and roasted regular and decaffeinated Coffea arabica and Coffea canephora beans were tested. MIC, biofilm inhibition and biofilm reduction results were correlated with the concentration of coffee compounds in the extracts. 5-Caffeoylquinic acid, trigonelline and caffeic acid solutions showed bacteriostatic activity (MIC = 0.8 mg/mL). Lighter and regular extracts showed higher inhibitory activity than darker and decaffeinated extracts, with an inverse correlation between bacterial colony-forming units and roasting degree. Only regular C. canephora extracts showed biofilm formation inhibition. The joint effect of chlorogenic acids, trigonelline and caffeine or other compounds removed by decaffeination seems to be one of the causes for coffee antibacterial activity against S. mutans.     

Supercritical CO2 decaffeination of unroasted coffee beans produces melanoidins with distinct NF-κB inhibitory activity

The supercritical CO(2)-decaffeination process causes unroasted coffee beans to turn brown. Therefore, we suspected that the decaffeinated beans contained melanoidins. Decaffeinated unroasted coffee extract absorbed light at 405 nm with a specific extinction coefficient, K(mix 405 nm), of 0.02. Membrane dialysis (molecular weight cut-off, 12 to 14 kDa) increased the K(mix 405 nm) value 15 fold. Gel filtration chromatography showed that the high-MW fraction (MW > 12 kDa) had an elution profile closer to that of melanoidins of medium-roast coffee than to the corresponding fraction of unroasted coffee, indicating the presence of melanoidins in decaffeinated unroasted beans. Using murine myoblast C2C12 cells with a stably transfected nuclear factor-κB (NF-κB) luciferase reporter gene, we found that the high-MW fraction of decaffeinated unroasted beans had an NF-κB inhibitory activity of IC(50) = 499 μg/mL, more potent than that of regular-roast coffee (IC(50) = 766 μg/mL). Our results indicate that melanoidins form during the supercritical CO(2)-decaffeination process and possess biological properties distinct from those formed during the regular roasting process. PRACTICAL APPLICATION: We discovered the roasting effect of decaffeination process, reporting the discovery of melanoidins in green (unroasted) decaf coffee beans. Our results indicated that melanoidins form during the supercritical CO2-decaffeination process and possess biological properties distinct from those formed during the regular roasting process. Our results offer new insights into the formation of bioactive coffee components during coffee decaffeination process.     

Investigation on the extractability of melanoidins in portioned espresso coffee

Coffee melanoidins have attracted interest as a result of its potential health benefits. This investigation aims to elucidate the extraction behavior of melanoidins and their populations during the preparation of portioned espresso coffee and its relationship with the antioxidant activity of the coffee brew. Filter-paper pods, FAP capsule, and clone capsule containing light roasted coffee have been investigated. An accumulative fractionation approach has applied to model the extraction kinetics of melanoidins, melanoidin populations, browning, chlorogenic acids (CGA), and antioxidant activity. Melanoidins were very efficiently extracted in clone capsules since less than 9 s was necessary to extract the 50% of the melanoidin content as compared with pods and FAP capsules, and the kinetic of extraction is slower than CGA. The extraction profile of melanoidins and browning fitted better with the antioxidant capacity than CGA and total solids profile. Melanoidin populations were obtained according to ethanol solubility. Total melanoidin content and the ratio between melanoidin populations did not change during extraction volume for espresso coffee. Melanoidin populations soluble at 75% ethanol showed the highest antioxidant activity. However, melanoidins with higher antioxidant activity are extracted at higher volumes. This investigation could make possible the adjustment of the technological requirements of espresso coffeemakers to produce an espresso coffee with high levels of beneficial compounds.     

Quantification of 3-aminopropionamide in cocoa, coffee and cereal products

Based on recent results confirming 3-aminopropionamide (3-APA) as a very effective precursor of acrylamide in the absence of further “catalysts”, this compound was quantified for the first time in cocoa masses, cocoa beans, coffee and cereal products by LC–MS–MS after derivatisation with dansyl chloride. Cocoa masses contained >3000 μg/kg of 3-APA, but varied significantly in its concentration. For the quantification of acrylamide (AA) in cocoa and coffee, an improved isolation procedure using charcoal was developed. In various samples of unroasted and roasted cocoa beans, the concentrations of AA were by a factor of >5 lower than those of 3-APA, but the concentrations of 3-APA and AA were more closely correlated as compared to the concentrations of AA and Asparagine. Experiments on authentic cocoa beans from Ghana and Sulawesi indicated that the thermal generation of 3-APA during roasting was much more pronounced as compared to its biochemical formation. By administering fermented cocoa beans with [¹³C₄ ¹⁵N₂]-asparagine before roasting, 3-APA was confirmed as transient intermediate in AA formation during cocoa roasting. Among the cereal products analysed, in particular popcorn contained quite high amounts of 3-APA, which were also well correlated with the AA concentration. Contrary, in coffee products, 3-APA was always lower than AA.     

咖啡中丙烯酰胺的形成与控制研究进展

丙烯酰胺是一种广泛存在于热加工食品中的危害物,咖啡是其重要的摄入来源之一。本文阐述了丙烯酰胺肝脏毒性、神经毒性、生殖毒性在动物和细胞水平上的表现,总结了咖啡豆高温烘焙过程中生成丙烯酰胺的主要途径。在咖啡原料选择、烘焙加工至萃取冲泡的过程中,影响丙烯酰胺形成的因素包括咖啡豆种类、烘焙温度、烘焙时间、贮藏条件等,且不同品类咖啡的加工方式也会造成丙烯酰胺含量差异。本文归纳了抑制咖啡中丙烯酰胺形成的有效措施,可为食品工业化生产中丙烯酰胺的控制提供理论参考。     

Effects of roasting degree on radical scavenging activity,phenolics and volatile compounds of Arabica coffee beans (Coffea arabica L. cv. Catimor)

We investigated the effect of roasting degree on volatile and phenolic compounds of coffee beans (Coffea Arabica L. cv. Catimor). The colour, 1,1‐diphenyl‐2‐picrylhydrazyl radical‐scavenging activity and phenolic acids of the aqueous extracts were studied. For the colour, L and b values were increased with an increase in roasting degree. Increasing roasting degrees led to a decrease in radical‐scavenging activity. Maximum radical‐scavenging activity was observed for the light‐roasted coffee. Chlorogenic acid was the most predominant amongst the ten phenolic acids identified, in green and all roasted beans. Syringic acid, p‐coumaric acid, gallic acid and sinapic acid increased with an increase in roasting degree. The volatile compounds were analysed using gas chromatography and mass spectroscopy. Aldehyde was the major volatile compound in green coffee. Our study has demonstrated that light‐roasted coffee gave the most desirable quality of roasted coffee with respect to phenolic content and radical‐scavenging activities.