Understanding flavour perception of espresso coffee by the combination of a dynamic sensory method and in-vivo nosespace analysis

The first goal of this work was to gain insight into the mechanism underlying flavour perception and aroma release by coupling two real-time methods: Temporal Dominance of Sensations (TDS) and nosespace (NS) analysis via Proton Transfer Reaction–Time of Flight–Mass Spectrometry (PTR–ToF–MS). The second goal was to investigate the impact of roasting degree and sugar addition on aroma release and perception in espresso coffee.A set of four coffee samples, two roasting degrees and two sugar levels, has been used for both sensory and instrumental measurements. The in-mouth flavour evolution in terms of dominant sensations was measured by mean of TDS carried out by 18 trained judges with a 9-attribute list (Sweet, Sour, Bitter, Astringent, Roasted, Burnt, Caramel, Nutty and Vegetal). The same judges were subjected simultaneously to NS analysis in order to identify and quantify the volatile compounds reaching their olfactory receptors during coffee consumption.A significant effect of roasting was observed with both techniques. More compounds and in larger quantity were released when increasing roasting degree, which was described sensorially as a greater dominance of the attributes Burnt, Roasted, Astringent and Bitter. Sugar addition did not significantly affect the aroma release of volatile compounds as demonstrated by the NS profiles of judges while changing completely the way the coffee was sensorially perceived in mouth. As expected, sweet taste became dominant over bitter and sour but it increased more globally the flavour complexity with Caramel and Nutty notes reducing the Roasted or Burnt ones. This result emphasises the presence of taste–smell perceptual interactions, due to congruence effect between sweet taste and some flavours of coffee, and the potentialities of this combination of dynamic methods to study them. Besides, the treatment of NS data using clustering methods revealed two different release behaviours, which permitted to identify potential TDS markers.     

Coffee beans microstructural changes induced by cultivation processing: An X-ray microtomographic investigation

The present work reports on the microstructural characterisation of four types of different processed coffee beans, Coffea arabica, Arabica monsooned, Coffea canephora and Robusta monsooned, by means of X-ray microtomography technique (μCT). A three dimensional (3-D) quantitative analysis was carried out on the microstructure the bean samples before and after roasting. The 3-D microstructure information provides a better understanding of the structure of the beans and from an engineering perspective; knowledge about the microstructure can be used to identify the important processing parameters that affect the quality of coffee. With regards to the microstructure, the porosity increase can summarise the overall effects of the roasting process on coffee beans. Results demonstrate the success of μCT for the quantification of the microstructural alterations of the coffee beans induced by their different cultivation processes before and after the roasting process.     

Use of macro and trace elements as biological markers in the lesser grain borer,Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The relationship between the occurrence and movements of Rhyzopertha dominica (F.), a serious pest of stored cereal grains, in distinctly different habitats is poorly known. Understanding the feeding ecology and dispersal patterns of R. dominica may likely help predict the abundance or movement of this pest in various habitats. Natal sites and movement of insects are studied using intrinsic methods involving elemental analyses. In this study, to understand the dietary history of R. dominica, trace and macro elements were used as potential markers. Insects reared on selected diets under laboratory conditions and adult beetles collected from the periphery of granaries or inside forested woodlands were used to determine 10 different elements in their body tissues. Quantities of 10 elements were also determined in respective laboratory hosts. The main discriminant elements for laboratory-reared R. dominica were Na, S and Zn, while significantly different elements were distinctive among field-collected beetles and included P, Ca, K, Zn, and Cu. The amount of Zn quantified in acorn-fed lab reared beetles was significantly lower than wheat- or corn-fed insects. Similarly, beetles captured in woodlands had significantly lower Zn in their body signatures, suggesting acorn seeds may have served as an alternate host in Quercus spp. dominated woodlands. Our studies showed that elemental profiles may potentially be used as biological markers for delineating food sources of R. dominica to mainly discriminate whether beetles originated in agricultural vs. wooded habitats.     

Provenance establishment of coffee using solution ICP-MS and ICP-AES

Statistical interpretation of the concentrations of 59 elements, determined using solution based inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma emission spectroscopy (ICP-AES), was used to establish the provenance of coffee samples from 15 countries across five continents. Data confirmed that the harvest year, degree of ripeness and whether the coffees were green or roasted had little effect on the elemental composition of the coffees. The application of linear discriminant analysis and principal component analysis of the elemental concentrations permitted up to 96.9% correct classification of the coffee samples according to their continent of origin. When samples from each continent were considered separately, up to 100% correct classification of coffee samples into their countries, and plantations of origin was achieved. This research demonstrates the potential of using elemental composition, in combination with statistical classification methods, for accurate provenance establishment of coffee.     

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.     

Outer membrane protein A (OmpA) may be used as a novel target to enrich and detect Escherichia coli in milk samples

In recent years, food safety incidents caused by Escherichia coli have occurred and have endangered human health. Due to the complex matrix of milk samples and the long pretreatment time, the existing methods cannot quickly detect E. coli in milk samples. It is necessary to enrich the E. coli in the complex matrix to improve the detection sensitivity. The E. coli outer membrane protein A (OmpA) is widely present on the cell membrane of E. coli and may be used as a new target to enrich E. coli. In this study, the purified recombinant OmpA protein was used to immunize BALB/c mice to produce polyclonal antibody. Immunomagnetic beads were combined with the polyclonal antibody to enrich the E. coli in the artificially contaminated milk samples. The products of immunoprecipitation were further used for PCR assay. The bacteria in the PCR sample can be pre-enriched, and the limit of detection is 10 × 10⁰ cfu/mL, which is about 100 times more sensitive than samples not processed by this method. Then, the artificially contaminated milk, coffee, juice, and soybean milk samples were tested separately, and it was found that the E. coli gene could be amplified. The whole analysis time was about 120 min, including the enrichment of bacteria and the detection of eluate. We found that OmpA combined with immunomagnetic beads was more efficient, fast, and convenient than the conventional method. Bacteria can be enriched more efficiently without extracting genomic DNA and culturing bacteria. Therefore, this method has potential value for improving the detection sensitivity and shortening the detection time of E. coli in food samples.     

Characterization of arabica and robusta roasted coffee varieties and mixture resolution according to their metal content

The metal content of roasted coffee samples belonging to the arabica and robusta varieties and coffee blends has been analysed. Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr, Zn have been determined by inductively coupled plasma atomic emission spectrometry. Principal component and cluster analysis have been applied to characterize the coffee varieties. P, Mn and Cu have been found to be the most discriminating variables. Partial least squares regression was applied to determine the relative content of each variety in the coffee blends. This method has been applied to determine the percentage of the robusta variety in some commercial roasted coffee samples.     

Geographical Differentiation of Green Coffees According to Their Metal Content by Means of Supervised Pattern Recognition Techniques

The contents of Ca, Cu, Fe, K, Mg, Mn, Na and Zn have been determined in green coffee beans from Brazil, Colombia and Mexico by means of inductively coupled plasma optical emission spectrometry. The concentrations of these elements were used to differentiate the coffee provenance. Kruskal–Wallis test highlighted significant differences between elemental contents from the three origins, and principal component analysis showed trends of samples to appear separately. Supervised pattern recognition techniques, such as linear discriminant analysis and soft independent modeling of class analogy, were used to obtain models allowing the geographical authentication of coffee samples with high reliability. Prediction abilities of 97 and 94 % were respectively obtained.     

Tasting atmospherics: Taste associations with colour parameters of coffee shop interiors

Coffee is one of the world’s most frequently consumed beverages, and coffee culture is an increasingly popular phenomenon across the world. Atmospheric elements are especially important for the design of coffee shops. However, it is still unclear how the visual atmospherics (e.g., colour scheme, lightness) of coffee shop interiors influence the consumer’s evaluations of coffee shops and their expectations concerning the coffee beverages they serve. The present research was designed to understand the role of one aspect of the visual atmosphere, namely the colour parameters of the interiors of coffee shop, on the consumer evaluation of the coffee shops themselves and on the expected sensory properties of the coffees served there. Ratings of taste expectations, likelihood of visiting, and emotions were evaluated for each of 50 coffee shop images and averaged across 65 participants. The color parameters (L*, a*, b*, saturation) of the coffee shop interior were calculated using digital image analysis. The results demonstrate that more reddish and lighter coloured coffee shop images were associated with the expectation that the coffee shop would serve a sweeter coffee, while more greenish and darker coloured coffee shop images were associated with more sour/bitter/tastier coffee expectations as well as a higher likelihood of visiting. Moreover, emotions, specifically feelings of calmness, mediated the relation between color parameters and taste expectations/likelihood of visiting. Taken together, these results provide evidence on the role of visual atmospherics of coffee shops on consumer evaluations and provide a number of practical implications for the coffee outlets/cafes.     

Coffee and tea choices and intake patterns in 20-to-40 year old adults

The main aim of this study was to analyze coffee and tea intake patterns considering body weight status and polymorphism of genes involved in bitter taste sensitivity. A group of normal weight and overweight or obese subjects aged 20–40 (n = 411) was recruited in Poznań, Poland. Three-day dietary records were used to assess daily intakes. Single nucleotide polymorphisms (SNPs) were genotyped using TaqMan SNP probes (TAS2R38: rs713598, rs1726866, rs10246939) or the high-resolution melting method (CA6 rs2274333). 67.2% of the group drank coffee and 70.6% drank tea. Drinking only coffee was associated with higher body mass index (BMI) (OR = 4.81, p = 0.041). BMI ≥ 25 kg/m² was associated with higher coffee intake (p = 0.010) and lower tea intake (p = 0.003). Higher taste-sensitivity of TAS2R38 gene was associated with a preference for bitter white coffee (OR = 1.74, p = 0.033). Over 50% of respondents ate sweet snacks while drinking coffee or tea. Consumption of sweet snacks was associated with drinking bitter black coffee (p = 0.044, OR 1.97) and sweet white coffee (p = 0.003, OR 2.92) and with BMI below 25 kg/m² (p = 0.016, OR = 0.51).Coffee and tea intake differed by body weight status. PAV haplotype (TAS2R38) was associated with a preference for bitter white coffee. The majority of the study group drank coffee and tea with additives (sugar, milk etc.) and ate sweet snacks with them.     

Trace elements of Taiwanese dioscorea spp. using instrumental neutron activation analysis

Twenty-two varieties categorized into six distinct species of dioscorea spp. had their concentration of trace elements evaluated by instrumental neutron activation analysis. The various dioscoreas were planted in the same plantation area to effectively suppress the diversity from different planted land, thus, the disagreement between each trace element was concluded from the nature of various species of dioscoreas themselves. Nineteen trace elements were verified and a quantified index, AT, was introduced to help classify the elements. A smaller AT indicated a close consistency of the concentration for specific trace element in various dioscorea. Thus, K, Zn, and Rb were in Group 1, which had the minimum ATs, Cl, Na, Mg, Fe, Mn, Br, and Co were in Group 2, which had the medium ATs, while the remaining of the trace elements, V, As, Sb, Cu, Se, Al, La, Sc, and Sm were all in Group 3, which had the maximum ATs. The different ATs and various species of dioscoreas were also discussed.     

Assessment of antimicrobial activity of coffee brewed in three different ways from different origins

The antimicrobial effect against pathogens such as Staphylococcus aureus, Enterecoccus faecalis, Listeria monocytogenes, Pseudomonas aeruginosa, Escherichia coli and Salmonella choleraesius was determined in four types of coffee (Coffea arabica L. cv. Colombia, decaffeinated cv. Colombia, cv. Ethiopia and cv. Kenya). Coffee was seen to have significant activity against the growth of food spoilage bacteria. Among the Gram-positive bacteria, coffee was strongly active against S. aureus, moderately active against L. monocytogenes and had a slightly inhibitory effect against E. faecalis. However, coffee samples were found to be less active against Gram-negative bacteria. The results show that espresso Colombia coffee has better antimicrobial activity than filter and Italian coffee with significant differences (p?<?0.05). Taking into account the origin, there were significant differences (p?<?0.05) between Kenya and decaffeinated Colombia, on the one hand, and Ethiopia and Colombia coffee, on the other, the two last showing the highest antimicrobial activity. The antimicrobial activity of the coffee from different origins studied in this paper increased with concentration. Typical coffee compounds were also analysed, and only caffeic and chlorogenic acids showed any inhibitory effect against the growth of all the analysed bacteria. The antibacterial properties of coffee means that it has a promising potential as natural food ingredient to extend the shelf life of foods such as cake, cookies or biscuits, coffee flavoured with shakes, yoghurt.     

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.     

Reprint of “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.     

Does roasted coffee contain chlorogenic acid lactones or/and cinnamoylshikimate esters?

Coffee is one of the most popular and consumed beverages in the world with many positive health effects. In this study the chlorogenic acid lactones and cinnamoylshikimate esters, a subclass of phenolics, from seven commercial roasted Robusta coffee samples were detected and characterized by LC–MSⁿ (n = 2–4). This is the first time when cinnamoylshikimate esters are reported in roasted coffee based on their tandem MS data. We used a previously developed LC–MSⁿ method to distinguish between chlorogenic acid lactones and cinnamoylshikimate esters. Chlorogenic acid lactones and their isomeric shikimate esters have identical m/z values in their MS spectra but different tandem MS spectra and retention times. Structures of these chlorogenic acid lactones and shikimate esters were assigned on the basis of LC–MS³ patterns of fragmentation, relative hydrophobicity and fragmentation analogy to the synthetic standards of mono-acyl chlorogenic acid lactones and shikimate esters containing moieties of ferulic, caffeic, p-coumaric and dimethoxycinnamic acids. Furthermore, 7 unknown and 52 known mono and diacyl chlorogenic acids were identified and characterized to their regioisomeric level. The study is relevant for profiling chlorogenic acids and their dehydration derivatives, shikimates and lactones, in roasted coffee.     

Factors affecting tocopherol contents in coffee brews: NP-HPLC/FLD,RP-UPLC-ESI/MSn and spectroscopic study

Qualitative and quantitative determination of tocopherols in filtered and unfiltered coffee brews was investigated. The NP-HPLC/FLD and RP-UPLC-ESI/MSⁿ techniques as well as fluorescence spectroscopy turned out to be very useful tools not only to estimate tocopherol contents, but also to detect contaminants in coffee brew tocopherol extracts. In all analysed coffee brew samples, only α- and β-T were detected. In Arabica coffee brews, the content of the β homologue was three to four times higher than that of the α homologue; however, in Robusta, they were almost identical. Unfiltered coffee brews contained about ten times more tocopherols, 3.02–5.26 and 3.39–16.52, than filtered brews, 0.4–0.71 and 1.26–1.77 μg/100 ml for α-T and β-T, respectively. The reduction in the size of ground coffee beans from 0.7 to 0.3 mm increases the concentration of tocopherols almost three times. Suspended coffee bean dust was the main source of tocopherols in coffee brews.     

Roasting-induced changes in arabinotriose,a model of coffee arabinogalactan side chains

Thermal processing can promote reactions that change the structure of food constituents, often by unknown mechanisms, such as those occurring in arabinose residues of coffee arabinogalactan side chains. Aiming to know more about these modifications, the structurally related α-(1 → 5)-l-arabinotriose was roasted at 200 °C and the products obtained were identified by ESI-MS and MALDI-MS and characterised by ESI-MSⁿ. Depolymerised and polymerised oligosaccharides with up to 16 residues and new types of linkages were formed. Also, products resulting from dehydration, oxidation, and cleavage of a carbon–carbon bond at the reducing end of the corresponding non-modified oligosaccharide were formed, probably promoting the release of formaldehyde, formic acid, glycolaldehyde, glyoxal, acetic acid, glycolic acid, glyceraldehyde, 2-hydroxypropanedialdehyde and lactic acid. As many of these compounds have been reported to occur in roasted coffee beans and/or brews, it can be suggested that the degradation of coffee arabinogalactan side chains can contribute to their formation upon roasting.     

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.     

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.