1,721,059 research outputs found
Espresso Coffee preparation: analytical study to improve the quality of the product
Full text linkThe PhD project was divided into three main parts. The first part aimed to develop and optimize
efficient and simply methods for the quantification of nine phytoestrogens in green coffee, and three
lignans in ground and espresso coffee (EC), using HPLC-MS/MS. For this purpose, different
extraction processes, i.e., acid and base hydrolysis, enzymatic hydrolysis, organic solvent extraction,
and a combination of these, have been studied. The best performing procedures, in term of recovery
and quantitative data, were chosen, validated and finally applied to different samples coming from
diverse geographical origins. The final objective was to characterize the content of these compounds
in the whole coffee chain, from green beans to cup. The second part concerned the optimization of
espresso coffee extraction, by modifying some machine variables aiming to produce a good quality
espresso coffee, lowering the amount of coffee powder used for espresso preparation. The variables
under study were the particle size distribution (PSD) of roast and ground (R&G) coffee, the design
of the filter basket and the height of perforated disc. The EC quality was investigated from chemical
point of view and it concerned the total solids (TS) analysis and the quantification of caffeine,
chlorogenic acids and trigonelline. In addition, some analysis on volatile fraction were also
performed. The third part of the project focused on promoting and adding value to coffee silverskin
(CS) in the perspective of its application in the food industry. The work aimed to characterize the
odor-active compounds in CS and compare them with those present in coffee beans. The
characterization of aroma fraction was carried out by gas chromatography-olfactometry/flame
ionization detector (GC-O/FID) and by comparing the odors and odorants with those found in coffee
beans. The identification was carried out by comparing with reference compounds the retention index
and the odor quality. Finally, for unequivocal identification, after fractionation, the samples were
analysed into comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-
MS). Moreover, the Aroma Extract Dilution Analysis (AEDA) was performed to assess the potency
of each odors/odorants.
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Regarding the phytoestrogen characterization, we found two enzymatic digestions, i.e., clara-diastase
(Method 3.10-EC) and taka-diastase (Method 5-R&G), as the most performing processes for lignan
extraction from espresso and R&G coffee, respectively. Secoisolariciresinol was the lignans present
at the highest concentration in espresso (27.9-52.0 μg L-1) and in R&G coffee (84.4-257.8 μg kg-1).
Moreover, the extraction yield of lignans revealed that they are almost completely extracted during
coffee percolation. For green coffee matrix, the best performing process was Method 7-GC, a double
extraction composed of base hydrolysis in MeOH and enzymatic digestion with clara-diastase and
we found that lignans (total content: 286.5-8131.8 μg kg-1) were more abundant than isoflavones
(total content: 3.4-300.0 μg kg-1). Our studies on espresso coffee optimization showed higher levels
of TS, caffeine, trigonelline and chlorogenic acids for reference samples (ECs extracted with mixed
particles) and for 200-300 μm mesh size, when standard filter (A) was set in the machine. By
decreasing the amount of R&G coffee, similar TS levels and contents of bioactive compounds to
standard condition, were obtained for reference compounds. The best filter baskets, in term of
quantitative data, were A and B and the study on perforated discs suggested that using lower amount
of ground coffee permits to obtain the same extraction yield increasing the height of perforated disc.
From our investigations on CS, four volatile compounds were identified for the first time in coffee.
In detail, 4-methyloctanoic acid and trans-4,5-epoxy-(E)-2-decenal were characterized in coffee
beans and silverskin, while 6-acetyl-2,3,4,5-tetrahydropyridine and 5-methyl-2-methoxyphenol only
in coffee beans. The highest flavour dilution (FD) factors in CS were obtained for furaneol, 2-
methoxy-4-vinylphenol and 2-methoxyphenol and, moreover, other typical coffee aroma volatiles
were found, e.g., 2-furfurylthiol, 2,3-butanedione, vanillin, 2-isobutyl-3-methoxypyrazine, etc. Some
aromas, such as furaneol, 2-methoxy-4-vinylphenol, vanillin, trans-4,5-epoxy-(E)-2-decenal, 2-
acetyl-1-pyrroline and 2-acetylpyrazine, occurred with similar FD factors in CS and coffee beans.
Our studies demonstrated that CS contains an interesting odor-active compound fraction with high
similarity to coffee beans
How different particle sizes of ground coffee influence the extraction of a good espresso coffee
No full textIntroduction: Espresso coffee (EC) is one of the most widely consumed beverages in the world and particularly in Italy. EC is different from other types of coffee, with its dense cream, mouthful flavor and attractive aroma [1]. This research aims to study the influence of ground coffee’s particle sizes on the EC extraction.
Methods: Quantitative and qualitative analyses are carried out on the two most common coffee cultivars, Arabica and Robusta. Experiments with different averages of particle sizes (200-400 and 400-1000 microns) are performed through previously developed methods [2], in order to check optimal level of bioactive and volatile compounds at the end of the extraction. The samples are analyzed by GC-MS and HPLC-VWD.
Results: EC extraction time, kinetics of extraction and its dependence on water pressure and temperature were controlled during the analyses. Bioactive compounds as caffeine, trigonelline, nicotinic acid, chlorogenic acids (CQAs) and volatiles were identified [3]. EC extractions were performed in duplicate for each particle size. Results confirmed a good extraction efficiency of caffeine, which accounted for 170 mg per cup at 200-400 microns and 90 mg at 400-1000 microns. Likewise, the amount of all other bioactive compounds increased when extracting coffee with smaller particle sizes.
Conclusions: EC extraction at different particle sizes was evaluated by analyzing the content in bioactive components and volatiles that were found in EC. Extraction optimization will be enhanced by modifying extraction variables.
References
[1]
C. Severini, I. Ricci, M. Marone, A. Derossi, and T.De Pilli, "Changes in the Aromatic Profile of Espresso Coffee as a Function of the Grinding Grade and Extraction Time: A Study by the Electronic Nose System," Agricultural and Food Chemistry, vol. 63, pp. 2321-2327, 2015.
[2]
Giovanni Caprioli, Manuela Cortese, Gloria Cristalli, Filippo Maggi, Luigi Odello, Massimo Ricciutelli, Gianni Sagratini, Veronica Sirocchi, Giacomo Tomassoni, Sauro Vittori, "Optimization of espresso machine parameters through the analysis of coffee odorants by HS-SPME-GC/MS," Food Chemistry, vol. 135, no. 3, pp. 1127-1133, 2012.
[3]
Jose A. Sanchez Lopez, Marco Wellinger, Alexia N. Gloess, Ralf Zimmermann, Chahan Yeretzian, "Extraction kinetics of coffee aroma compounds using a semi-automatic machine: On-line analysis by PTR-ToF-MS," International Journal of Mass Spectrometry, vol. xxx, pp. xxx-xxx, 201
Optimization of extraction variables for espresso coffee
No full textKHAMITOVA, Gulzhan*,**, ANGELONI, Simone*,**, CAPRIOLI, Giovanni*, SAGRATINI, Gianni*, VITTORI, Sauro. *,**
*University of Camerino, Camerino, MC, Italy,
**International HUB for Coffee Research and Innovation.
RATIONALE
Espresso coffee (EC) extraction is a convoluted process due to effect on physical and chemical variables to the final cup. Beyond these parameters, size of grinded coffee plays crucial role to extract good espresso with tantalizing aroma, dense cream and mouthfeel flavor [1]. Coffee particles are made by a large number of compounds. An understanding of these compounds can be helpful for process optimization and quality control. This research aims at analyzing the levels of compound variation at specific particle size distribution (200-400 and 400-1000 microns).
METHODS
Quantitative and qualitative analyses are carried out through HPLC-VWD and GC-MS [2]. The espresso machine settings are maintained at 9 bar and 92±20C. Particle sizes between 200-400 and 400-1000 microns were used to prepare EC.
RESULTS
EC extraction time, kinetics of extraction and its dependence on water pressure and temperature were controlled during the analysis. Analytes as caffeine, trigonelline, nicotinic acid, chlorogenic acids (CQAs) and volatiles were identified. EC extraction were performed in duplicate for each particle size. Results confirmed a good extraction efficiency of caffeine, which accounted for 170 mg (200-400 microns) and 90 mg per cup (400-1000 microns), respectively. Thus, amount of bioactive compounds was increased extracting smaller particle sizes.
CONCLUSIONS & PERSPECTIVES
EC extraction of different particle sizes was analyzed for their content in bioactive components and volatiles normally found in EC. Extraction optimization will be developed by modifying extraction variables.
REFERENCES
[1] Britta Folmer, Imre Blank, Adriana Farah, Peter Giuliano, Dean Sandres and Chris Wille, The Craft and Science of Coffee, London, UK: Elsevier, 2017.
[2] Giovanni Caprioli, Manuela Cortese, Gloria Cristalli, Filippo Maggi, Luigi Odello, Massimo Ricciutelli, Gianni Sagratini, Veronica Sirocchi, Giacomo Tomassoni, Sauro Vittori, "Optimization of espresso machine parameters through the analysis of coffee odorants by HS-SPME-GC/MS," Food Chemistry, vol. 135, no. 3, pp. 1127-1133, 2012
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Development of a New Analytical Method to Quantify Lignans in Coffee by HPLC-MS/MS.
No full textA new analytical method to quantify three lignans in espresso coffee have been developed and validated by using HPLC-MS/MS Triple Quadrupole. Different extraction methods (acidic and enzymatic hydrolisis) have been tested and the best extraction process have been chosen after validation for application to real coffee samples
From 7-dehydrocholesterol to vitamin D3: Optimization of UV conversion procedures toward the valorization of fish waste matrices
Full text linkVitamin D, a fat -soluble steroid, has increasingly taken a central role due to its crucial role in human health. It is estimated that about 40% of worldwide population are vitamin D deficient. The fish industry produces significant quantities of waste daily, with consequent high environmental impact. The aim of this work is to place a first brick for the fish waste reuse as a source of vitamin D-3 extracts to be used for nutraceutical purposes. For this purpose, an UV conversion method for transforming the 7-dehydrocholesterol, highly present in fish, in vitamin D-3 has been optimized. The UV wavelength, exposure time, temperature, stirring, and UV intensity were optimized using a surface response design tool. The optimized treatment was applied to five fish species with different fat percentages and the results were very promising reaching vitamin D-3 levels >10 times higher than the pre-treatment ones
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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