Extraction kinetics of coffee aroma compounds using a semi-automatic machine: On-line analysis by PTR-ToF-MS

López, Jorge Expósito; Wellinger, Marco; Gloess, Alexia N.; Zimmermann, Ralf; Yeretzian, Chahan

doi:10.1016/j.ijms.2016.02.015

Cited by 51 publications

(23 citation statements)

References 22 publications

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“…The approach we consider here is agglomerative hierarchical clustering, which describes the degree of similarity between any two measurements and can be used to sort species into categories of behavior (Bar-Joseph et al, 2001;Müllner, 2011). Hierarchical clustering analysis (HCA) has been used to group particles based on the similarity between individual mass spectra determined by aerosol mass spectrometers (Marcolli et al, 2006;Murphy et al, 2003;Rebotier and Prather, 2007), describe time-series of thermally-desorbed organics measured by CIMS (Sánchez-López et al, 2014;Sánchez López et al, 2016), and recently to determine the appropriate number of PMF factors used to analyze PTR-MS data from chamber studies (Rosati et al, 2019). It has not yet been used to group compounds with similar timevarying behaviors to understand chemical transformation in an oxidation system.…”

Section: Hierarchical Clustering Analysis (Hca)mentioning

confidence: 99%

Dimensionality-reduction techniques for complex mass spectrometric datasets: application to laboratory atmospheric organic oxidation experiments

Koss¹,

Canagaratna²,

Zaytsev³

et al. 2019

Preprint

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<p><strong>Abstract.</strong> Oxidation of organic compounds in the atmosphere produces an immensely complex mixture of product species, posing a challenge both for their measurement in laboratory studies and their inclusion in air quality and climate models. Mass spectrometry techniques can measure thousands of these species, giving insight into these chemical processes, but the data sets themselves are highly complex. Data reduction techniques that group compounds in a chemically and kinetically meaningful way provide a route to simplify the chemistry of these systems, but have not been systematically investigated. Here we evaluate three approaches to reducing the dimensionality of oxidation systems measured in an environmental chamber: positive matrix factorization (PMF), hierarchical clustering analysis (HCA), and a parameterization to describe kinetics in terms of multigenerational chemistry (gamma kinetics parameterization, GKP). The evaluation is implemented by means of two data sets: synthetic data consisting of a three-generation oxidation system with known rate constants, generation numbers, and chemical pathways; and the measured products of OH-initiated oxidation of a substituted aromatic compound in a chamber experiment. We find that PMF accounts for changes in the average composition of all products during specific periods of time, but does not sort compounds into generations or by another reproducible chemical process. HCA, on the other hand, can identify major groups of ions and patterns of behavior, and maintains bulk chemical properties like carbon oxidation state that can be useful for modeling. The continuum of kinetic behavior observed in a typical chamber experiment can be parameterized by fitting species' time traces to the GKP, which approximates the chemistry as a linear, first-order kinetic system. Fitted parameters for each species are the number of reaction steps with OH needed to produce the species (the generation) and an effective kinetic rate constant that describes the formation and loss rates of the species. The thousands of species detected in a typical laboratory chamber experiment can be organized into a much smaller number (10&#8211;30) of groups, each of which has characteristic chemical composition and kinetic behavior. This quantitative relationship between chemical and kinetic characteristics, and the significant reduction in the complexity of the system, provide an approach to understanding broad patterns of behavior in oxidation systems and could be exploited for mechanism development and atmospheric chemistry modeling.</p>

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Section: Hierarchical Clustering Analysis (Hca)mentioning

confidence: 99%

Dimensionality-reduction techniques for complex mass spectrometric datasets: application to laboratory atmospheric organic oxidation experiments

Koss¹,

Canagaratna²,

Zaytsev³

et al. 2019

Preprint

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“…From an engineering viewpoint, coffee brewing is considered a solid-liquid extraction, where the roasted and ground coffee is in intimate contact with water. The water acts as a solvent to extract the water-soluble compounds, and depending on the extraction technique used, insoluble compounds may also be present in the extraction water as dissolved or suspended solids 11 . Finally, volatile and non-volatile flavour compounds are extracted from the ground coffee and are dispersed in the final coffee beverage 12 .…”

Section: Introductionmentioning

confidence: 99%

Effect of grinding, extraction time and type of coffee on the physicochemical and flavour characteristics of cold brew coffee

Córdoba

Pataquiva

Osorio

et al. 2019

Sci Rep

117

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The effects of grinding (medium-coarse) and extraction time (14–22 h) on the physicochemical and sensorial properties of cold brew coffee produced using two types of Colombian specialty coffees (Huila and Nariño) were evaluated. Cold coffee brewed under coarse grinding and 22 h of extraction exhibited the highest values of total dissolved solids, extraction yield, pH, titratable acidity (TA), and total phenolic content. The type of coffee used mainly affected the TA and pH. All cold brew coffee samples had lower TA values than their hot counterparts. Nariño cold brew samples had higher TA values than those of Huila in all treatments evaluated. Higher scores were reported in the sensorial evaluation of cold brew coffee when prepared using the shortest time (14 h) and coarse grinding for both coffee types. These coffees were characterized by strong sweetness, fruity and floral flavours, medium bitterness and acidity, and a creamy body. Furans, pyrazines, ketones, aldehydes, pyrroles, esters, lactones, furanones, and phenols were detected as odour-active compounds. The findings of this study demonstrate that the particle size, contact time, and coffee type affect the physicochemical and sensorial characteristics of cold brew coffee, leading to cold brew coffees with different flavour profiles.

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“…Prior work has shown that the perception of sweetness increases in the presence of sweet‐associated aromas, even if no sweet taste stimulation is being perceived . Previous chemical studies have been conducted on the rates of extraction of various aroma compounds from coffee, with Sánchez López et al . performing online proton transfer reaction time‐of‐flight mass spectrometry showing different groupings of when aroma compounds extracted during the brewing process.…”

Section: Discussionmentioning

confidence: 99%

Sensory and monosaccharide analysis of drip brew coffee fractions versus brewing time

et al. 2020

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BACKGROUND The composition of drip brew coffee versus brewing time has been chemically characterized in previous studies, and it is known that the total dissolved solids (TDS) systematically decreases with each fraction during the brew. Little information exists regarding the corresponding sensory attributes versus time, however, and it is unclear how TDS correlates with flavor profile. RESULTS Standard drip brews were fractionated into distinct samples by switching in an empty carafe every 30 s during the brew. Using a trained sensory descriptive panel, we found that most taste and flavor attributes decreased with brew time; for example, the earlier fractions were systematically more bitter and more sour than later fractions. Surprisingly, however, several flavor and taste attributes increased in time; for example, later fractions were systematically sweeter and more floral than earlier fractions. Since later fractions had lower TDS, these results indicate that perceived sweetness in drip brew coffee is negatively correlated with TDS. Mass spectrometry measurements of the monosaccharide content in the brews showed that none of the fractions had perceptible concentrations of any monosaccharide. CONCLUSION The results of the sensory analysis and the monosaccharide analysis suggest that perceptible sweetness in coffee is a consequence of masking effects and/or the presence of sweet‐associated aromas and flavors. The results further suggest that unique flavor profiles could be obtained from the same coffee grounds by judicious combinations of specific fractions. © 2020 Society of Chemical Industry

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Extraction kinetics of coffee aroma compounds using a semi-automatic machine: On-line analysis by PTR-ToF-MS

Cited by 51 publications

References 22 publications

Dimensionality-reduction techniques for complex mass spectrometric datasets: application to laboratory atmospheric organic oxidation experiments

Dimensionality-reduction techniques for complex mass spectrometric datasets: application to laboratory atmospheric organic oxidation experiments

Effect of grinding, extraction time and type of coffee on the physicochemical and flavour characteristics of cold brew coffee

Sensory and monosaccharide analysis of drip brew coffee fractions versus brewing time

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