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Book of Abstracts Research and Innovation Centre Fondazione Edmund Mach (2023). Proceedings of the DIFFA23 - 1st International Symposium on Direct Injection Food Flavour Analytics, fmach, Italy (9788878430600), A fast-GC PTR-ToF-MS method coupled to an autosampler, for analysis of volatiles above ground coffee samples has been developed and validated. The results have shown that many of the molecular formulas detected by PTR-ToF-MS, commonly associated with coffee volatiles are actually numerous compounds as separated by fast-GC.

Third wave coffee has its origin in the 1970s when coffee businesses started sourcing high-quality specialty coffee and delivering it freshly roasted to consumers. Over the past decade specialty coffee has become ubiquitous, and its market share has continuously grown. Presently, there is no consensus about what the fourth wave could be like. One of the developments has been the emergence of heavily fermented coffees. These exhibit very characteristic, clearly defined, and intense aromas and command a price up to 100-times higher than the commodity market price. Arabica coffee from the farm Iris Estate, Geisha variety, has been post-harvest processed by three methods: washed (W), pulped natural (PN), and fermented by so-called ‘carbonic maceration’ (CM). The aim was to elucidate the impact of CM on the flavour profile, as compared to the W and PN process. Sensory evaluation had revealed that CM creates characteristic flavour notes that were described as raspberry with hint of rose water. The aroma compounds of the roasted and ground coffee were analysed using solid-phase micro extraction gas chromatography (SPME-GC) and detected by both sniffing (GC-O) and mass spectrometry (GC-MS). The study found six compounds that are considered contributing to the characteristic raspberry flavour of the CM coffee. These compounds were consistently identified as intense with raspberry notes when sniffing CM coffee, but not in W coffee. Three out of the six were identified and characterized by means of MS, whereas the other three were detected only by GC-O and could not be characterised by MS. The link of an experimental fermentation post-harvest processing technique to characteristic flavour compounds and sensory notes in the cup could be established. Such studies may ultimately allow such coffees to become scalable and more readily available for everyone to experience and enjoy.

Conference documentation: Armin Hansel, Jürgen Dunkl (Eds.) (2024): 9th International Conference on Proton Transfer Reaction Mass Spectrometry and its Applications, Innsbruck University Press (ISBN 978-3-99106-119-9), A fast-GC PTR-ToF-MS method coupled to an autosampler, for analysis of volatiles above ground coffee samples has been developed and validated. The results have shown that many of the molecular formulas detected by PTR-ToF-MS, commonly associated with coffee volatiles, are composed of numerous overlapping compounds, as demonstrated by fast-GC separation prior to PTR-ToF-MS analysis.

The aroma of freshly roasted coffee is one of its most enticing but also ephemeral qualities. Coffee aroma starts deteriorating after roasting, and appropriate packaging and storage are needed to preserve its freshness. After a coffee package has been opened, the protective atmosphere changes, accelerating the loss of freshness and staling of coffee. This study compares four different methods for storing whole roasted beans after opening the package: (i) transferring beans into airtight canister, (ii) closing original package with tape, (iii) closing with clip and (iv) using a package with an integrated screw cap. The aroma was analyzed during storage by gas chromatography mass spectrometry (GC/MS), after grinding. Freshness indices were determined as ratios of GC/MS signal intensities of two selected compounds and used as indicators of storage stability (also called index), to compare different storage approaches. The 2-butanone/2-methylfuran index was found to be best suited to assess coffee staling for such conditions. The screw cap packaging was the best performing storage method. Using a clip, re-closing with tape or transferring beans into a container resulted in a faster loss of freshness. Findings were in line with observed changes in oxygen and carbon dioxide content inside the respective package. While changes of coffee during the primary shelf-life of coffee have been discussed in a series of publications, this study is one of the first that sheds light on how consumer practices can influence the secondary shelf-life of whole bean coffee.

We report, on the successful addition of spray-dried microparticles containing roasted coffee oil, to soluble coffee (SC) and instant cappuccino (IC), to increase and tailor aroma release. Using PTR-ToF-MS (Proton Transfer Reaction Time-of-Flight Mass Spectrometry), five parameters were defined from time series intensity for each VOC, to compare the performance of different products: total area under the curve (AUC), area under the curve of burst (AUC-burst), maximum signal intensity, final intensity (5 min), and ratio AUC-burst/AUC. Microparticles with higher loads of roasted coffee oil were effective in increasing aroma intensity in SC while, for IC, all loads of microparticles improved aroma intensity. Volatility drove the VOC release in SC, and volatility and polarity for IC. Most compounds reached maximum headspace concentration in < 16 s upon start of reconstitution. These results open new perspectives for the development of instant coffee products and demonstrate their unique aroma release characteristics.

This article is part of the special issue of the Flavour and Fragrance Journal entitled “On‐line monitoring of odorants using direct‐injection mass spectrometry” edited by Jean‐Luc Le Quere., Changes in the headspace volatile profile of tea infusion during brewing were determined by analysing the aliquots taken every 30 s using proton transfer reaction time‐of‐flight mass spectrometry in conjunction with principal component analysis and hierarchical cluster analysis. The effect of three different brewing temperatures (60, 70 and 80°C), two leaf sizes (broken and full leaves) and two water mineralizations (soft and hard), on the concentration of volatile compounds in the headspace of tea, was studied as a function of infusion time. An increase in brewing temperature resulted in increased volatile content in the headspace, reflecting an increase in extraction efficiency. Such differences on extraction efficiency were more pronounced with increasing brewing times. Leaf size had also a big impact on the extraction of volatile compounds, but mainly during the early phase of brewing. Water mineralization had a low but noticeable impact on the volatile content. Furthermore, clusters of samples prepared with different combinations of brewing parameters but resulting in analogous volatile profiles could be identified using hierarchical clustering analysis.

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.

We present three cases of on-line sampling of coffee aroma and coupling to PTR-MS. Each case studied involves processes occurring on different time scales and at varying conditions, therefore diverse sampling techniques were developed for successful coupling.

During the roasting of coffee, thermally driven chemical reactions lead to the formation of gases, of which a large fraction is carbon dioxide (CO2). Part of these gases is released during roasting while part is retained inside the porous structure of the roasted beans and is steadily released during storage or more abruptly during grinding and extraction. The release of CO2 during the various phases from roasting to consumption is linked to many important properties and characteristics of coffee. It is an indicator for freshness, plays an important role in shelf life and in packaging, impacts the extraction process, is involved in crema formation, and may affect the sensory profile in the cup. Indeed, and in view of the multiple roles it plays, CO2 is a much underappreciated and little examined molecule in coffee. Here, we introduce an accurate, quantitative, and time-resolved method to measure the release kinetics of gases from whole beans and ground coffee using a gravimetric approach. Samples were placed in a container with a fitted capillary to allow gases to escape. The time-resolved release of gases was measured via the weight loss of the container filled with coffee. Long-term stability was achieved using a customized design of a semimicro balance, including periodic and automatic zero value measurements and calibration procedures. The novel gravimetric methodology was applied to a range of coffee samples: (i) whole Arabica beans and (ii) ground Arabica and Robusta, roasted to different roast degrees and at different speeds (roast air temperatures). Modeling the degassing rates allowed structural and mechanistic interpretation of the degassing process.

Coffee is a major source of dietary antioxidants; some are present in the green bean, whereas others are generated during roasting. However, there is no single accepted analytical method for their routine determination. This paper describes the adaption of three complementary assays (Folin-Ciocalteu (FC), ABTS and ORAC) for the routine assessment of antioxidant capacity of beverages, their validation, and use for determining the antioxidant capacities of extracts from coffee beans at different stages in the roasting process. All assays showed a progressive increase in antioxidant capacity during roasting to a light roast state, consistent with the production of melanoidins having a higher antioxidant effect than the degradation of CGAs. However, the three assays gave different numbers for the total antioxidant capacity of green beans relative to gallic acid (GA), although the range of values was much smaller when chlorogenic acid (CGA) was used as reference. Therefore, although all three assays indicated that there was an increase in antioxidant activity during coffee roasting, and the large differences in responses to GA and CGA illustrate their different sensitivities to different types of antioxidant molecule.

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.

Coffees from different origins were roasted to different roast degrees and along varying time temperature roasting profiles. The formation of volatile organic compounds (VOCs) during roasting was analyzed online by proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Coffee samples were Coffea arabica from Colombia, Guatemala (Antigua La Ceiba), Ethiopia (Yirga Cheffe, Djimmah) and Coffea canephora var. robusta from Indonesia (Malangsari). The roasting profiles ranged from high temperature short time (HTST) to low temperature long time (LTLT) roasting, and from medium to dark roast degree. The release dynamics of the on-line monitored VOCs differed for the different coffees and showed a strong modulation with the time–temperature roasting profile. While for Guatemalan coffee the formation of VOCs started relatively early in the roasting process, the VOC formation started much later in the case of Yirga Cheffe and Malangsari. Off-line analysis of the coffee brew augmented the measurements. These included headspace solid phase micro extraction gas chromatography mass spectrometry (HS SPME GC/MS), content of total solids, chlorogenic acids, caffeine, total polyphenols (Folin Ciocalteu), organic acids (ion chromatography), titratable acidity and pH. Some general trends, irrespective of the coffee origin, were observed, such as an increase in pH when going from an HTST to an LTLT profile or from a medium to dark roast degree. Furthermore, a decrease of total headspace intensity was observed from an HTST to an LTLT roasting profile. In general, the changes of the time temperature roasting profiles and/or the roast degree influenced the intensity of the respective coffee constituents as well as their relative composition differently for different coffee origins.