Identification of odor-active 3-mercapto-3-methylbutyl acetate in volatile fraction of roasted coffee brew isolated by steam distillation under reduced pressure

Insights on Single-Dose Espresso Coffee Capsules' Volatile Profile: From Ground Powder Volatiles to Prediction of Espresso Brew Aroma Properties

Single-dose coffee capsules have revolutionized the coffee market, fueling espresso coffee popularity and offering access to a wide selection of coffee blends. Nevertheless, scarce information related to coffee powder and brew’s combined volatile characterization is available. In this study, it is hypothesized that coffee brew aroma characteristics can be predicted based on coffee powder’s volatile composition. For this, headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC × GC-ToFMS) was used. The data were combined via chemometric tools to characterize in depth the volatile composition of eight blends of capsule-coffee powder and respective espresso brews, simulating the consumer’s perception. A total of 390 volatile compounds were putatively identified, 100 reported for the first time in roasted coffee or brews. Although the same chemical families were determined among the coffee powders and espresso brews, a different volatile profile was determined for each matrix. The Pearson correlation of coffee powders and respective brews allowed to identify 15 volatile compounds, mainly terpenic and esters recognized by their pleasant notes, with a strong relationship between the amounts present in both matrices. These compounds can be key markers to predict the volatile aroma potential of an espresso brew when analyzing the coffee powder.

Characterization of Odor-Active Compounds of Ichang Lemon (Citrus wilsonii Tan.) and Identification of Its Genetic Interspecific Origin by DNA Genotyping

Ichang lemon is a citrus fruit whose rind gives off a delicious and much appreciated fragrance and flavor. The volatile components of the fruit peel of Ichang lemon were investigated by GC-MS and GC-O (AEDA method). Simultaneously, its genetic origin was identified by using diagnostic SNP markers specific to ancestral species and multiallelic SSR and InDel markers. Ichang lemon combines three ancestral genomes (Citrus maxima, Citrus ichangensis, and Citrus reticulata) and may be a pummelo × Yuzu hybrid. Although the major compounds of the Ichang lemon aromatic profile were present in Citrus junos, a few pummelo-specific compounds were also detected, such as indole and nootkatone, in agreement with its maternal lineage. 3-Methyl-3-sulfanylbutyl acetate, reported to occur in passion fruit and brewed coffee, was identified by GC-MS, GC-QTOF-MS, and GC-FTIR for the first time in citrus. This odor-active compound has a sulfurous, tropical fruity, green note.

Spotlight on release mechanisms of volatile thiols in beverages

Volatile thiols are very strong-smelling molecules that can impact the aroma of numerous beverages. Several thiols and thiol precursors have been reported previously in different plants used as raw material for beverages, some of which are fermented. We focused on thiols in beverages and their release mechanisms from precursors during processing. Volatile thiols in beverages can be classified aslow molecular weight volatile thiols (e.g. H₂S, methanethiol) which impact the smell negatively, and volatile thiols with higher boiling points that contribute positively to the aroma profile. The first part of this review is devoted to volatile thiols, without considering small malodorous molecules. The second part deals with thiol precursors and the different release mechanisms induced by processing (e.g. extraction, roasting or fermentation) and by the growing methods (e.g. viticulture), which can impact on amounts of thiols and their precursors.

Metabolomics fingerprint of Philippine coffee by SPME-GC-MS for geographical and varietal classification

Volatile metabolites of Philippine Arabica and Robusta coffee beans in both forms standard (not-eaten by the Asian palm civet) and civet coffee grown in different Philippine regions were identified using the hyphenated technique headspace-solid phase microextraction-gas chromatography-mass spectrometry. A great number of volatile metabolites with a wide variety of functional groups were extracted and forty-seven prominent compounds were identified. The volatile metabolomics (volatilomics) fingerprint of Arabica coffees considerably differed from Robusta coffee and geographical origin slightly altered the fingerprint profile of coffee samples. Chemometric analysis such as principal component analysis (PCA) displayed a good classification between Arabica and Robusta coffee samples. Although Arabica coffee samples from different geographical origins were clustered separately from each other, the proximity of clusters between Arabica coffee samples which could be classified into one large group, indicated their close similarity of headspace metabolites. The distinction between Arabica samples and Robusta coffees was attributed through the PCA to several key volatile metabolites, in particular, higher quantities of acetic acid, furfural, 5-methylfurfural, 2-formylpyrrole and maltol and lower concentrations of 4-ethylguaiacol and phenol. These discriminating metabolites could represent useful quality markers to differentiate Arabica from Robusta coffee. Results revealed that the headspace metabolites in coffee provide significant information on its inherent aroma quality. Also, the findings suggested that the overall quality of Philippine coffee is variety and region-specific.

Sustained Nitric Oxide Release from a Tertiary S-Nitrosothiol-based Polyphosphazene Coating

Nitric oxide (NO) occurs naturally in mammalian biochemistry as a critical signaling molecule and exhibits antithrombotic, antibacterial, and wound-healing properties. NO-forming biodegradable polymers have been utilized in the development of antithrombotic or antibacterial materials for biointerfacial applications, including tissue engineering and the fabrication of erodible coatings for medical devices such as stents. Use of such NO-forming polymers has frequently been constrained by short-term release or limited NO storage capacity and has led to the pursuit of new materials with improved NO release function. Herein, we report the development of an NO-releasing bioerodible coating prepared from poly[bis(3-mercapto-3-methylbut-1-yl glycinyl)phosphazene] (POP-Gly-MMB), a polyphosphazene based on glycine and the naturally occurring tertiary thiol 3-mercapto-3-methylbutan-1-ol (MMB). To evaluate the NO release properties of this material, the thiolated polymer POP-Gly-MMB-SH was applied as a coating to glass substrates and subsequently converted to the NO-forming S-nitrosothiol (RSNO) derivative (POP-Gly-MMB-NO) by immersion in a mixture of tert-butyl nitrite (t-BuONO) and pentane. NO release flux from the coated substrates was determined by chemiluminescence-based NO measurement and was found to remain in a physiologically relevant range for up to 2 weeks (6.5-0.090 nmol of NO·min^-1·cm^-2) when immersed in pH 7.4 phosphate-buffered saline (PBS) at 37 °C. Furthermore, the coating exhibited an overall NO storage capacity of 0.89 ± 0.09 mmol·g^-1 (4.3 ± 0.6 μmol·cm^-2). Erosion of POP-Gly-MMB-NO in PBS at 37 °C over 6 weeks results in 14% mass loss, and time-of-flight mass spectrometry (TOF-MS) was used to characterize the organic products of hydrolytic degradation as glycine, MMB, and several related esters. The comparatively long-term NO release and high storage capacity of POP-Gly-MMB-NO coatings suggest potential as a source of therapeutic NO for biomedical applications.

Identification of the odour-active cyclic diketone cis-2,6-dimethyl-1,4-cyclohexanedione in roasted Arabica coffee brew

We investigated odour-active trace compounds in roasted Brazilian Arabica coffee. Aroma dilution extract analysis (AEDA) applied to the volatile oil extracted from roasted coffee brew revealed 34 odour-active compounds. Among these, a pungent-smelling unknown odour-active compound was determined. The volatile oil was fractioned by silica gel column chromatography. Gas chromatography-olfactometry (GC-O) and multidimensional gas chromatography-mass spectrometry (MDGC-MS) of the fraction which contained a significant amount of the target unknown compound revealed the cyclic 1,4-diketone, cis-2,6-dimethyl-1,4-cyclohexanedione, which had a pungent odour, and was thus first identified in roasted coffee. Model experiments revealed that cis-2,6-dimethyl-1,4-cyclohexanedione was formed via thermal degradation of sugars, especially monosaccharides, under alkaline conditions. Further, we demonstrated that 2-hydroxy-3-pentanone and 1-hydroxy-2-propanone, thermal degradation products of monosaccharides, were closely related to the formation of cis-2,6-dimethyl-1,4-cyclohexanedione.

Tentative identification of volatile flavor compounds in commercial Budu, a Malaysian fish sauce, using GC-MS

Budu is a famous Malaysian fish sauce, usually used as seasoning and condiment in cooking. Budu is produced by mixing fish and salt at certain ratio followed by fermentation for six months in closed tanks. In this study, four commercial brands of Budu were analyzed for their chemical properties (pH, salt content and volatile compounds). The pH of Budu samples ranged from 4.50-4.92, while the salt (NaCl) content ranged between 11.80% and 22.50% (w/v). For tentative identification of volatile flavor compounds in Budu, two GC columns have been used, DB-WAX and HP-5MS. A total of 44 volatile compounds have been detected and 16 were common for both columns. 3-Methyl-1-butanol, 2-methylbutanal, 3-methylbutanal, dimethyl disulfide, 3-(methylthio)-propanal, 3-methylbutanoic acid and benzaldehye have been identified as the aroma-active compounds in Budu due to their lower threshold values.

Headspace solid-phase microextraction-gas chromatographic-time-of-flight mass spectrometric methodology for geographical origin verification of coffee

Increasing consumer awareness of food safety issues requires the development of highly sophisticated techniques for the authentication of food commodities. The food products targeted for falsification are either products of high commercial value or those produced in large quantities. For this reason, the present investigation is directed towards the characterization of coffee samples according to the geographical origin. The conducted research involves the development of a rapid headspace solid-phase microextraction (HS-SPME)-gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) method that is utilized for the verification of geographical origin traceability of coffee samples. As opposed to the utilization of traditional univariate optimization methods, the current study employs the application of multivariate experimental designs to the optimization of extraction-influencing parameters. Hence, the two-level full factorial first-order design aided in the identification of two influential variables: extraction time and sample temperature. The optimum set of conditions for the two variables was 12 min and 55 degrees C, respectively, as directed by utilization of Doehlert matrix and response surface methodology. The high-throughput automated SPME procedure was completed by implementing a single divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) 50/30 microm metal fiber with excellent durability properties ensuring the completion of overall sequence of coffee samples. The utilization of high-speed TOFMS instrument ensured the completion of one GC-MS run of a complex coffee sample in 7.9 min and the complete list of benefits provided by ChromaTOF software including fully automated background subtraction, baseline correction, peak find and mass spectral deconvolution algorithms was exploited during the data evaluation procedure. The combination of the retention index (RI) system using C(8)-C(40) alkanes and the mass spectral library search was utilized for the confirmation of analyte identity in the reference authentic Brazilian coffee sample. The semi-quantitative results were then submitted to statistical evaluation, namely principal component analysis (PCA) for the establishment of geographical origin discriminations.

Gas chromatography-olfactometry in food flavour analysis

The application of gas chromatography-olfactometry (GC-O) in food flavour analysis represents to be a valuable technique to characterise odour-active, as well as character impact compounds, responsible for the characterizing odour of a food sample. The present article briefly reviews the use of GC-O in the flavour investigation of dairy products (milk and cheese), coffee, meat and fruits. Particular attention has been devoted to extraction techniques, GC-O hardware commonly utilised and olfactometric assessment methods, which can be applied to food analysis.

Reliable characterization of coffee bean aroma profiles by automated headspace solid phase microextraction-gas chromatography-mass spectrometry with the support of a dual-filter mass spectra library

This investigation is based on the automated solid phase microextraction GC-MS analysis of the volatile fraction of a variety of coffee bean matrices. Volatile analytes were extracted by headspace (HS)-SPME which was achieved with the support of automated instrumentation. The research was directed towards various important aspects relating to coffee aroma analysis: monitoring of the volatile fraction formation during roasting; chromatographic differentiation of the two main coffee species (Arabica and Robusta) and of a single species from different geographical origins; evaluation of the influence of specific industrial treatments prior to roasting. Reliable peak assignment was carried out through the use of a recently laboratory-constructed "flavour and fragrance" library and a dual-filter MS spectral search procedure. Further emphasis was placed on the automated SPME instrumentation and on its ability to supply highly repeatable chromatographic data.

Comprehensive multidimensional GC for the characterization of roasted coffee beans

The present investigation is based on the separation of one of the most complex food matrices: the roasted coffee bean volatile fraction. Analysis of the two main species of coffee (Arabica/Robusta) was achieved through an effective and simple sampling procedure, headspace solid-phase microextraction (SPME), and the unprecedented resolving power of comprehensive gas chromatography (GC x GC). The combination of these two techniques proved to be a powerful tool for the extraction and separation of coffee volatiles. In fact, thousands of compounds that play various roles in the constitution of coffee aroma profile were resolved in the 2-D contour plot, each occupying a specific position pinpointed by two retention time coordinates. The potential use of this method for the assessment of coffee quality and the detection of commercial fraud is discussed. The potential of GC x GC for identification and classification of unknowns was also demonstrated, as the formation of characteristic patterns for structurally related compounds was observed in the bidimensional chromatogram. Moreover, reproducibility results were supported by the use of an autosampler for SPME applications that allowed any inaccuracy arising from manual handling to be avoided.