Caffeine content in coffee as influenced by grinding and brewing techniques

The caffeine content of coffee as influenced by various coffee preparation methods was investigated. The variables studied included the coffee solids to water volume ratio, the volume of coffee prepared, home versus store grinding, and drip/filtered versus boiling. Caffeine contents per 177 ml (6 oz) of coffee ranged from 50 to 143 mg, depending upon the mode of preparation. As expected, more coffee solids and larger extents of grinding led to significantly higher caffeine contents in filtered coffee. Larger volumes of coffee prepared at a constant coffee solids to water ratio also yielded significantly higher caffeine contents. Homegrinding yielded caffeine contents similar to that of store-ground coffee. Boiled coffee had caffeine contents equal to or greater than filtered coffee, depending upon the length of boiling time. The variable caffeine contents in coffee resulting from the mode of preparation should be recognized and addressed by both food composition data bases and epidemiologists.     

Norharman and harman in instant coffee and coffee substitutes

Norharman and harman are two neuroactive β-carbolines present in several plants and thermally processed foods, including roasted coffee. The objective of this study was to evaluate their amounts in commercial instant coffee-based and coffee substitute beverages (n = 48), with variable amounts of coffee, chicory, barley, malt, and rye. All samples contained variable amounts of both β-carbolines, always with a higher proportion of norharman than harman. The highest levels (p < 0.01) were found in 100% instant coffees, with mean amounts of 3.8 μg/g and 1.5 μg/g for NH and H, respectively, followed by plain chicory. The lowest amounts were found in 100% barley, with 1.1 μg/g for NH and 0.3 μg/g for H. The NH and H content was statistically higher (p < 0.01) in all mixtures with coffee when compared to those without it. Nevertheless, and except for 100% barley, the amounts provided by beverages based on coffee substitutes are within those reported for standard coffee brews.     

Overview on the mechanisms of coffee germination and fermentation and their significance for coffee and coffee beverage quality

Quality of coffee is a complex trait and is influenced by physical and sensory parameters. A complex succession of transformations during the processing of seeds to roasted coffee will inevitably influence the in-cup attributes of coffee. Germination and fermentation of the beans are two bioprocesses that take place during post-harvest treatment, and may lead to significant modifications of coffee attributes. The aim of this review is to address the current knowledge of dynamics of these two processes and their significance for bean modifications and coffee quality. The first part of this review gives an overview of coffee germination and its influence on coffee chemistry and quality. The germination process initiates while these non-orthodox seeds are still inside the cherry. This process is asynchronous and the evolution of germination depends on how the beans are processed. A range of metabolic reactions takes place during germination and can influence the carbohydrate, protein, and lipid composition of the beans. The second part of this review focuses on the microbiota associated with the beans during post-harvesting, exploring its effects on coffee quality and safety. The microbiota associated with the coffee cherries and beans comprise several bacterial, yeast, and fungal species and affects the processing from cherries to coffee beans. Indigenous bacteria and yeasts play a role in the degradation of pulp/mucilage, and their metabolism can affect the sensory attributes of coffee. On the other hand, the fungal population occurring during post-harvest and storage negatively affects coffee quality, especially regarding spoilage, off-tastes, and mycotoxin production.     

The use of advanced chemometric techniques and trace element levels for controlling the authenticity of organic coffee

This study examines the application of advanced data mining techniques associated with trace element concentrations for authenticity evaluation of organic coffee samples. Fifty-four coffee samples (20 organic and 34 non-organic) were evaluated according to their macro and microelement contents to establish reference ranges and identify differences in patterns of chemical elements in both crop procedures. Inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of thirty-eight chemical elements (Al, As, B, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Dy, Eu, Er, Gd, Ge, Ho, La, Lu, Mn, Mo, Ni, Pb, Rb, Se, Sm, Sr, Yb, W, U, Ta, Tb, Th, Ti, Tl, Zr and Zn). In general, higher levels of chemical elements were found in conventional coffee compared with organic samples. The classification of samples was performed by using three well known data mining algorithms, named Multilayer Perceptron (MLP), Support Vector Machine (SVM) and Naïve Bayes (NB). When all analyzed variables were considered, a 96.3% accuracy level was obtained with the three algorithms. The level of accuracy remained at 96.3% for SVM and MLP and rose to 98.2 for NB when only eight of the investigated minerals – i.e. Zn, Se, Ba, U, Dy, Tl, Th, Mo – were used for chemometric analysis. This level of accuracy provides a strong foundation to propose the combination of trace element spectral fingerprints with data mining techniques as a valuable tool to evaluate the authenticity of organic coffee samples.     

Ochratoxin A in commercial soluble coffee and coffee substitutes

Coffee and cereals are recognized sources of ochratoxin A (OTA) in the human diet, but data concerning its amounts in soluble coffee substitutes are scarce. This work aimed to determine the amounts of OTA in commercial soluble coffee substitutes (mixtures of barley, malt, and chicory, either with or without coffee). OTA was isolated by immunoaffinity columns and quantified by HPLC with fluorescence detection.In a total of 40 samples analyzed, including 10 of soluble coffee, 13 mixtures with coffee and 17 mixtures without coffee, all commercialized in Portugal, 35 samples were positive for OTA, with concentrations ranging from < 0.15 to 11.8 μg/kg. Overall, coffee-containing samples had significantly higher amounts of OTA (p < 0.001) than substitutes without coffee. Indeed, coffee was the main determinant for the OTA content in the substitute beverages analyzed, with a highly significant linear correlation (r = 0.559, p < 0.001) between OTA amounts and coffee percentage in the mixtures. The high variability observed between samples is influenced by the “brand” effect as well as by raw-material quality.Globally, OTA amounts in coffee substitutes are generally low and within the regulated and safety limits. Their contribution to the provisional tolerable daily intake (PTDI) is therefore reduced (from 1.0 to 2.0% on average). Nevertheless, the high incidence of OTA contamination in these products should not be disregarded.     

Extraction of coffee diterpenes and coffee oil using supercritical carbon dioxide

Commercial green and roasted coffee beans were used to maximize oil extraction and conditions were studied to obtain the highest and lowest diterpene levels on green and roasted coffee oil, respectively. Thus, operational temperatures (60–90 °C) and pressure (235–380 bar) were optimized for coffee oil extraction. Oil content levels and diterpene oil concentration were compared to the results obtained with the extraction with Soxhlet apparatus, using hexane as solvent. In general, an inverse correlation was observed between the amount of extracted oil and diterpene concentration levels. As a result, different oil contents with different diterpene concentrations could be obtained. The HPLC analysis of cafestol and kahweol in the oil extracted from green coffee beans at 70 °C/253 bar resulted in the highest concentration (453.3 mg 100 g⁻¹), which was 48% lower than in the oil extracted with hexane while in the oil extracted from roasted coffee beans at 70 °C/371 bar, resulted in 71.2% reduction of diterpenes.     

Recent developments in the manufacture of instant coffee and coffee substitutes

This paper describes modern production methods resulting from the developments that have been taking place recently in the field of instant coffee and coffee substitutes. Such developments involve new processing techniques to achieve higher extraction yields and improve extract concentration, and more efficient spray drying. A tabulated comparison of operating conditions when spray drying chicory, pure coffee and chicory/coffee mixtures is given.     

心动黑咖啡——韩延文的咖啡情结

和韩延文约好到中国歌剧舞剧院采访,眼前的她,时尚靓丽,白裙、黑靴,给人以时尚前卫感,出道十几年,她的脸上不仅没有留下岁月更替的痕迹,反倒因阅世闻事,虔心演艺事业而更具魅力。     

Roasted coffee oil microencapsulation by spray drying and complex coacervation techniques: Characteristics of the particles and sensory effect

The objective of this research was to microencapsulate roasted coffee oil using spray drying (SD) and complex coacervation (CC) techniques and to compare the microparticles properties and their sensory impact on the perception of soluble coffee brew aroma. Starch was used as wall material for spray dried microparticles (MSD), and gelatin and gum Arabic for that produced by complex coacervation (MCC). Ultrasound stable emulsions were obtained. Both microparticles presented a continuous wall and similar glass transition temperature (49.3 °C). MSD had 10.2% oil content and low surface oil content, and high solubility and wettability. MCC stood out for its high oil content (42.8%) and larger diameter (125 μm). Sensory evaluation showed that, when dissolved in hot water, microparticles provided a coffee aroma. Despite the MCC brew was preferred by assessors, the perception of coffee aroma intensity during the preparation of a soluble coffee brew containing MSD or MCC were similar.     

Chemical characterization and antioxidant properties of a new coffee blend with cocoa,coffee silverskin and green coffee minimally processed

The search for new technologies and ingredients with interesting characteristics and potential for incorporation into functional foods emerges in parallel with the demand for alternative sustainable and economically viable blends. Pursuing these aims, the formulation of a new coffee blend with 94% roasted coffee powder (Coffea canephora cv. Robusta and Coffea arabica, 70/30, w/w), 3% cocoa powder, 2% coffee silverskin and 1% golden coffee (green coffee minimally processed) was developed. The influence of the ingredients in the blend was compared with two other commercial coffee blends (in capsule and in a sealed package with a one-way degassing valve), being characterized the formulation, the physicochemical parameters, as its innovation. It is concluded that the developed coffee blend shows an enriched content of bioactive compounds (chlorogenic acids, trigonelline, theobromine and caffeine), displays an important antioxidant capacity and was favorably appreciated due to its sensory characteristics. Moreover, the addition of skin by-product becomes an additional valorization and the processing of green coffee and cocoa was minimized by adding innovation and an optimized extraction.     

The mycobiota of coffee beans and its influence on the coffee beverage

The quality of coffee beverage is influenced by several factors, including the species or botanical variety of the beans, agricultural practices, harvesting, drying and storage techniques and also the preparation of the beverage. Apart from these, there is the input of microbial contamination during the processing of the beans. Numerous studies have demonstrated that fungi are important contaminants of coffee beans, especially just after harvesting and drying. However, the relationship between fungal contamination and the sensorial characteristics of the beverage has yet to be described. The aim of this research was to analyze the mycobiota of coffee beans collected from different stages of the coffee production chain and to correlate these data with the sensorial characteristics of the final beverage. Fungal infection of 22 coffee bean samples from the southwest of São Paulo state was analyzed. Samples were collected from the tree (mature cherries), from the ground, from the patio (mature, immature and dried floaters or overripe cherries from the tree) and from storage facilities. In general, coffee samples from this region showed high fungal infection and contamination was higher than 70% in about 45% of the samples. A high diversity of fungi was isolated from all the coffee samples analyzed and the most common were Penicillium brevicompactum, Aspergillus section Nigri, Penicillium sp. nov. (closely related to Penicillium crustosum) and Fusarium sp. Both P. brevicompactum and Penicillium sp. nov. were found at all processing stages, including in the cherries, showing that these fungi are naturally found in the coffee beans from this region. Floater coffee and coffee from the ground showed negative sensorial evaluation with attributes such as moldy, dirty and fermented and presented a high contamination by Aspergillus section Nigri and Aspergillus westerdijikiae.     

咖啡渣油脂的提取及其脂肪酸组成研究

加工咖啡时剩下的残渣可用来提取天然植物油脂。用气-质联用仪分析咖啡油的组成,测出4种主要脂肪酸:亚油酸34.79%、油酸9.85%、棕榈酸42.12%、硬脂酸8.49%,油的脂肪酸组成较好,故咖啡油有一定的营养保健作用。     

The effect of dewaxing of green coffee on the coffee brew

The two commercially most important mild treatments for green coffee are the steam treatment and the dewaxing process. In the former treatment the green coffee is just steamed. In the dewaxing process the waxy layer is extracted from the green coffee with an organic solvent, after which this coffee is also steamed to remove solvent residues. Some of the main constituents of the waxy layer are the carboxy-5-hydroxytryptamides (C-5-HT). What happens to these components during the roasting and brewing of the coffee is discussed. During roasting part of the C-5-HT decomposes, but during brewing most of the C-5-HT remains in the spent grounds due to its insolubility.Literature reports about physiological effects of both types of coffee in human and animal experiments are summarised briefly. For both types of treated coffee additional evidence seems to be needed before hard conclusions can be drawn about their digestibility.     

International coffee standardisation and legislation

The author describes the particular technical features of coffee standards used commercially and/or legislatively. Existing national standards on green coffee and their harmonisation of terminology, sampling and test method are described and discussed. Comparisons are made of the various legislative standards of different countries with respect to instant coffee and their harmonisation within the EEC member countries. Roasted coffee is considered to a lesser extent as it is not an important element in the world trade for coffee. The role of various international organisations in standardisation is described. It is emphasised that the flavour of coffee is not amenable to international standardisation.