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This article contains data related to the research article entitled “Quantitative assessment of specific defects in roasted ground coffee via infrared-photoacoustic spectroscopy” (Dias et al., 2018) [1] . A method potentially able for assessing the quality of roasted ground coffees is described in the origin paper. Infrared spectroscopy and photoacoustic detection (FTIR-PAS) associated with multivariate calibration were used. The samples were obtained blending whole and healthy coffee beans (C. arabica and C. canephora) with specific blends of defects, named selections, which contain broken, sour, and black beans, skin, woods and healthy beans still not collected. In addition to a reduction in commercial value, the presence of defects compromises the sensory attributes of coffee. On the other hand, selections are commonly found in coffee crops and can be added intentionally to the product. Twenty-five selections were used to obtain a panel of 154 blends. The FTIR-PAS spectra of each sample generated the prediction model of Partial Least Squares Regression parameters, which are also presented here.

This study presents an experimental approach to study the kinetics and fast release of volatile organic compounds (VOCs) upon reconstitution of instant coffee products. A sampling setup coupled to PTR-ToF-MS (Proton Transfer Reaction Time-of-Flight Mass Spectrometry) for the automated and reproducible reconstitution of instant coffee products was developed to monitor the dynamic release of VOCs. A rapid release of aroma compounds was observed in the first seconds upon hot water addition ("aroma burst"), followed by subsequent decrease in headspace (HS) intensities over the course of analysis. Differences in time-intensity release profiles of individual VOCs were correlated to their Henry's Law constant, vapor pressure and water solubility. The setup and approach proposed here have shown to be sensitive and to respond to fast dynamic changes in aroma release. It allows studying VOCs release upon reconstitution and supports the development of novel technologies and formulations for instant products with improved aroma release properties.

Water is an essential ingredient for coffee extraction, typically making up more than 90% of the final beverage. This chapter introduces the basic characteristics of water and the most common dissolved contents. The concepts of water hardness and alkalinity are explained while discerning between technical and sensory aspects with regards to coffee extraction. The existing recommendations on the optimum water composition are discussed as well as the potential off-flavors that can arise from nonideal composition. As a link between a given water composition and a targeted recommendation the most common water treatment methods are systematically characterized. The chapter concludes with practical examples on the impact of different water compositions in a cupping experiment and espresso extraction.

Since the early days of the specialty coffee movement, freshness has been one of its central pillars. Freshness is best defined as having original unimpaired qualities. In coffee, it is most often seen as freshly roasted, ground within a few days, immediately extracted, and consumed. But despite this pivotal role of freshness for high quality coffee, the objective and scientific measurement of freshness have often been vague and elusive. How can one measure the level of freshness of coffee? In this chapter we will outline two approaches. One is based on the degassing of the freshly roasted coffee and the other on the evolution of its aroma profile during storage. In terms of the evolution of the aroma profile, we will introduce one particular freshness index: the ratio of dimethyl disulfide to methanethiol, suited to assess the evolution of freshness of roasted coffee during storage. Although this ratio has been shown to increase during storage, the speed at which this freshness index increases depends on the packaging and storage temperature. This has opened the possibility to use this index to assess the freshness of roasted coffee and compare the quality of different packaging materials for preserving the freshness of the coffee inside.

The quality of green coffee is influenced by the degree of ripeness of the fruit at harvest. The aim of this study was to identify chemical markers differentiating between degrees of ripeness. Two coffee varieties, Catuai and Tipica, from the same farm were analysed using the following parameters and methods: caffeine and chlorogenic acid content using high-performance liquid chromatography (HPLC), sucrose content using hydrophilic interaction chromatography, high-molecular weight fraction (HMW) using high-performance size-exclusion chromatography (HPSEC) and volatile compounds using headspace solid phase micro extraction gas chromatography/mass spectrometry. The best method for differentiating between degrees of ripeness was found to be principal component analysis (PCA) based on HPLC data. HPSEC showed differences in the HMW fraction for different degrees of ripeness and both coffee varieties. Volatile profiles allowed separation of both varieties; yet, except for ripe Catuai, no separation was achieved for the degree of ripeness.

This chapter describes the measurement of free radical processes in liquid coffee samples, and their impact on the quality and stability of the beverage. Free radicals generated during the roasting process are relatively stable and located in the polymeric melanoidins, but their concentrations change in coffee solutions via O2-independent decay and O2-dependent formation processes. In addition, the chemistry of coffee solutions is strongly influenced by highly unstable free radicals, presumably hydroxyl radicals generated via Fenton reaction chemistry. These radicals react virtually indiscriminately with organic molecules by hydrogen atom extraction, and can thus initiate progressive degradation of coffee brews. Identification of stable markers of such reactions are discussed along with possible strategies for slowing the rate of alteration of liquid coffee products during storage.

A platform composed of three complementary and validated antioxidant assays is proposed for the routine and fast assessment of the antioxidant capacity of coffee brews. Firstly, a brief review of the principles underlying antioxidant measurements in foods, and the rationale behind the development of an analytical platform for measuring the antioxidant capacity of coffee is given. A range of complementary methods is described based on either hydrogen atom or electron transfer reactions. Secondly, three total antioxidant capacity (TAC) assays are recommended for the platform. Two are based on electron-transfer reactions—the Folin–Ciocalteu (FC) assay for total phenols, and the ABTS assay, which on oxidation forms the cationic chromophore, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS•+). The third, which is based on hydrogen-atom transfer, is the oxygen radical absorbance capacity (ORAC), in which the antioxidant and the substrate fluorescein compete for thermally generated peroxyl radicals after their formation by decomposition of 2,​2′-​azobis-​2-​amidinopropane,​dihydrochloride (AAPH). Finally, validated protocols for conducting these three assays, using flow injection analysis (FIA), are presented along with actual results to illustrate their reproducibility and robustness. The three assays are combined into an analytical platform to profile and compare the antioxidant potential of a series of roasted coffee samples. Antioxidant values obtained with the same dark-roast coffee are 2103, 710, and 5868 gallic acid equivalents (GAE) for the FC, ABTS, and ORAC assays, respectively. These numbers thus reflect the different types of chemical reaction that are performed, and illustrate the fact that assays for TAC are actually selective (and hence complementary) for specific types of antioxidant molecule.

The influence of roasting and storage conditions on free radical contents of individual Arabica coffee beans was examined during storage of whole, half and ground beans in air over a 1-month period. Free radical contents increased with increasing roasting time (roasting degree), but the atmosphere (air vs. N 2 ) used in the roasting and cooling process had little effect. There was a progressive increase in free radical contents with storage time, but the rate was much lower in whole beans than with half and fully ground beans, for which the rate was similar. These results suggest that exposure to O 2 , rather than physical grinding is the main mechanism for storage-related free radical generation, and strongly indicate that roasted coffee is best kept as whole beans in order to minimise changes during prolonged periods of aerobic storage. Furthermore, they demonstrate that EPR measurements can contribute to understanding the process and storage related changes in coffee.

Because of the roles of free radicals in the formation of Maillard reaction products and as markers of oxidation processes in foods, the dynamics of free radical generation during the roasting of coffee beans have been measured, and some exploratory investigations conducted on the extent to which these are influenced by the bean type, and the atmosphere (air vs. N2), in which the beans were roasted and cooled. The intensities of the free radical signals from individual Arabica and Robusta coffee beans were measured continuously in an EPR spectrometer, whilst beans underwent heating/cooling cycles in air or N2 atmospheres. Additional EPR measurements were performed on the products of coffee beans roasted in a laboratory, convectional hot air roaster. Two sets of experiments were performed: (i) single/half bean roasting in air or N2, and real time, in situ EPR analysis of the free radical content – with a very high flow of roasting gas (convective roasting); (ii) batch roasting in air or N2, and EPR measurements of individual roasted beans – in a rather low flow of gas. Large differences in intermediate and final free radical EPR signal intensities were observed between the specimens of Arabica and Robusta beans that were investigated, irrespective of the roasting atmosphere. During the heating phase of the roasting process, only minor differences were observed between beans of the same type roasted in air or nitrogen, but the presence of oxygen in the cooling cycle resulted in major increases of free radical levels compared to those observed in an inert atmosphere, although this O2-related effect was not observed in beans from the convectional hot air roaster. Large bean to bean variations were observed with a standard blend roasted in the convectional hot air roaster, but much smaller variations were observed with beans from a single batch. Three major conclusions can be drawn from this study: (i) when roasting with a very strong flow of hot gas, the atmosphere (air vs. N2) had a very limited impact (during the heating phase) on free radical formation, but a dramatic and fast increase during the cooling phase, irrespective of the type of coffee beans. (ii) It appears that the relative masses of coffee beans and air during the roasting process are critical for oxidation and hence the free radical content of the final product. Indeed, the dramatic increase in free radicals during air-cooling was only observed if roasting was performed with a very high flow of hot air. (iii) There are wide variations in the free radical dynamics of different types of coffee bean. Arabica beans showed stronger free radical formation during roasting and higher EPR intensities at the end of the roasting cycle, than did Robusta beans. Yet, as the sampling over different Arabicas and Robustas was limited here, a more systematic study is needed to ascertain this observation.

Recently we introduced a dynamic approach to determine Henry’s law constants (HLCs) of volatile organic compounds (VOCs) in water, and applied it to a series organic compounds dissolved in pure water. Here, we first discuss a further development of the original approach such that it can be applied to complex liquid food systems (coffee). Second, we examine the impact of non-volatile constituents on the HLC. More specifically, we evaluate the impact of non-volatile coffee constituents on the HLC of 2-methylpropanal, 3- and 2-methylbutanal, dimethylsulfide, dimethyldisulfide and ethyl-2-methylbutyrate. Finally, we demonstrate that the concentration on the VOC in solution does not affect the HLC, over the investigated concentration range of 10−4 to 10 ppm.

An extensive analysis of the headspace (HS) of coffee brew using proton-transfer-reaction mass-spectrometry (PTR-MS) is presented. In particular, we present a set of methods that link mass spectral peaks, as observed in PTR-MS, to chemical compounds in the HS of coffee. Combining all this information, a tentative assignment and rough quantification of liquid coffee HS is presented. Coffee was chosen because it contains a large number of chemically diverse volatile organic compounds (VOCs), representing a challenging system for on-line analysis by PTR-MS.

Density functional studies of the abundant cluster Na6Pb and of its analogue Na6Mg are reported. The structure of Na6Pb has been optimized for a series of symmetry constraints (Oh, D3d, D3h, C5v, C3v and C2v). The resulting binding energies fall within a narrow range of less than 0.1 eV whereas a spread of more than 0.5 eV is calculated for Na6Mg. These findings indicate a high structural flexibility of Na6Pb. The Pb atom exhibits a propensity to occupy a highly coordinated site in contrast to Mg which, in the most stable structures, is attached to the ‘outside’ of a Na6 moiety. Analysis of the bonding mechanism revealed two major contributions which increase the atomization energy of Na6Pb compared to Na6Mg: an enhanced charge transfer from the Na6 subsystem and a stronger polarization of the Pb atom. A significant contribution to the overall cluster stability comes from the interaction between the alkali atoms.

Recently we reported on vibrationally resolved spectra of the ionic ground state of Ag 2 + via ZEKE spectroscopy. The vibronic intensity distributions could not be interpreted within the Franck-Condon scheme. Here, we show that it is possible to overcome this discrepancy by invoking the breakdown of the Born-Oppenheimer approximation in the ZEKE states of silver dimer. A comparison of the spectral structure of the direct ion signal with simultaneously recorded ZEKE band profiles further illustrates this non-Franck-Condon behavior.

We report on mass-analyzed ZEKE spectra of Ag+2 via resonance-enhanced two-color excitation. To the best of our knowledge, this is the first metal dimer and at the same time the heaviest system (218 amu) ever investigated by mass-analyzed ZEKE. The adiabatic ionization potential, vibrational energies for v+ = 1, 2, 3 and 4 as well as the vibrational constants ωe, ωeχe of the ionic ground state X2Σ+g are determined with high accuracy. The surprising intensity pattern of vibrational progressions cannot be rationalized within a Franck—Condon picture and points to the unique properties of ZEKE states.

In this article, recent cluster—surface collision experiments are reviewed from the perspective of fullerene research. A detailed description of the method and the reflectron time-of-flight surface collider (reflectron collider), designed and built in Los Angeles, will be given first, to show how pulsed cluster-ion-beams are mass and energy selected, collided with specific surfaces and the various outcomes studied. In the second part, we outline several applications together with the scientific impact surface collision experiments have had on several fullerene-related research subjects. This includes impact-induced dissociation experiments, to probe stability and structural resilience, rebound velocity distributions from solid surfaces to reveal energetic and dynamic aspects of the scattering process, and rates of delayed electron emission from impact-heated fullerenes. Impact experiments also have turned out to be a useful tool to examine structural hypotheses as demonstrated on coalescence products from fullerene—fullerene reactions, fullerene derivatives and on metallo-fullerenes.

Recent experiments have demonstrated that large fullerenes can form by coalescence in the hot and dense vapor produced by pulsed UV-laser desorption of a fullerene film. The abundance spectra exhibit masses both at and close to the primary coalescence product. We suggest a rate equation that reproduces this pattern, applicable to the nearly symmetric abundance distributions observed in coalescence with high laser fluence and also to the strongly asymmetric case of coalescence with low fluence. The equation is parameterized by three rates, which in the completely symmetric and in the completely asymmetric case reduces to two. In these two cases the relative abundances can be expressed by a single dimensionless parameter.

The soluble molecule La2C80 recently reported by Alvarez et al. exhibits a robustness similar to other fullerenes. It survives intact for ≈ 10−6s following impact against solid surfaces Si(100) at up to 200 eV, yielding an estimate Ef>4 eV for fragmentation processes. The high threshold for electron emission suggests that the electron affinity in La2C−80 is significantly larger than in C60. These facts seem to rule out an external site for either La atom and disfavor a network-site interpretation, and thus favor endohedral (encapsulation) sites. Among the possible cages, the Ih-C80 fullerene appears to be highly favorable for the oxidation state (La3+)2C6−80.

Controversy regarding the interpretation of photoionization efficiency measurements obtained for alkali clusters provided impetus for higher-resoln. (3.3 nm) studies . The new data cover the full range of cluster sizes: Nax, x