X-Ray Fluorescence in Biological Sciences. Группа авторов

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СКАЧАТЬ the elemental composition of roasted coffee grains and roasted ground coffee. The chemical composition of the packaged roasted ground coffee and the composition of the similarly roasted coffee grains ground immediately prior to the analysis were also compared. Measurements were performed at the Institute of Physics of the Federal University of Rio Grandi do Sul (Brazil, Ion Implantation Laboratory). A beam of protons with an energy of 2 MeV and Si (Li) a detector with energy resolution of 160 eV for radiation with an energy of 5.9 keV were used. C, O, and N are measured by the Rutherford Backscatter (RBS) method. The results showed that the coffee grain matrix consisted mainly of C, followed by O and N. PIXE results for roasted ground coffee and roasted coffee grains showed that K and Mg are the elements with the highest concentration, Zn and Sr are trace elements. Comparison of these two types of coffee showed that the contents of certain elements, particularly Mg, Cl, Ca, Fe, Zn, and Rb, are statistically significantly different. No clear picture of the origin of such differences has been revealed. Because of this, the correlation between these differences and the quality of the final drink has not been established. The authors note the possibility that factors such as processing and negligent harvesting leading to the inclusion of twigs and defective beans in frying processes and crushing may have influenced the results. The results obtained by the authors for Cl showed that packaged ground roasted coffee contained more of this element, compared with fresh ground coffee. Cl‐based compounds such as chloroanisoles are known to impart unpleasant odors to beverages such as wine and coffee, and these results are consistent with the fact that freshly ground coffee is generally thought to produce a better‐quality beverage. Green and roasted grains have the same chemical composition, indicating that none of the elements studied in this work are lost during the roasting process. All elements except Fe have the same concentrations in both kinds of grains. The distribution of elements over the surface of the grains is uniform, while the distribution within the grains shows certain patterns for different elements.

      In the work of Hernández et al. [86], an ED X‐ray spectrometer (Rh anode, silicon drift detector) was used to determine the contents of several elements from 11 to 38: Na, P, S, Cl, K, Ca, Mn, Fe, Cu, Zn, Br, Rb, and Sr. The sample material was dried at room temperature and the tablets were pelletized. The authors analyzed 11 samples of commercial ground coffee and compared the obtained data with a sample of instant coffee and two other samples of ground coffee. Calibration and validation of content determination accuracy was assessed by analyzing CRM‐certified NIST 1547 (peach leaves), 1570a (spinach leaves), 1573a (tomato leaves), and 1571 (orchid leaves). Generally, the measured content of the elements was little different for all coffee samples and did not exceed toxic levels. Nevertheless, differences between the contents of the elements are shown and discussed. The authors recommend collecting a more complete collection of coffee samples for future work. In such a collection it is necessary to significantly expand the range of samples for instant coffee.

      In a recently published article Debastiani et al. [87] continued research on Brazilian coffee by PIXE version. The authors investigated the change in the chemical composition of Brazilian coffee at various stages of the drip brewing process. For this purpose, more than 140 samples of 8 different Brazilian brands of ground coffee (original samples of ground coffee, material of spent coffee, and coffee beverage after paper filtration) were analyzed. Major conclusions from Debastiani et al. [87] are:

       Confirmed the remark of Debastiani et al. [85] about significant differences in concentrations of certain elements between coffee samples of different brands and between different batches of the same brand.

       K, Mg, P, Ca, and S proved to be elements with a higher concentration in Brazilian coffee.

       Analysis of spent coffee showed that the extraction coefficients are specific for each element (the highest extraction coefficients from ground coffee are obtained for Cl and K, then Rb and P).

       Paper filters do not transfer elements to coffee beverage.

3.6 Determination of the Elemental Composition of Krasnodar Tea Samples by TXRF and WDXRF

The paper Maltsev et al. [88], analyzed samples of several varieties of Krasnodar tea. This tea is the singular Russian tea product, the chemical composition of which was here studied for the first time. In practice the contents of 16 elements from phosphorus to lead have been determined. Nineteen commercially available samples of Krasnodar tea have been investigated. Table 3.4 shows the name, type, shape, and quality of each tea according to producer information on the package. Krasnodar tea plantations are the northernmost of all tea plantations in the world. Tea in the Krasnodar region has been grown since the beginning of the twentieth century. The first attempts to grow tea bushes brought from China proved unsuccessful. In the harsh winter, the bushes died. Only seeds brought from Georgia managed to grow tea. The first tea plantation appeared near the city of Sochi, in a valley of mountains 220 m above the sea. The history of Russian tea breeding began with this plantation. The tea qualities “granulated”, “long leaf,” and “packed” are common in the classification of tea quality.

One of the original types of Krasnodar tea is a skull tea. It is produced by two enterprises: Dagomys Chai Group of Companies and Matcsestin Tea Factory. It includes shank, stem particles, and tea leaf. This tea does not belong to the varieties of tea, but it is not inferior to other types of Krasnodar tea. In fact, in some parameters it exceeds many granulated and packaged varieties. Skull tea can be stored longer than usual. It is necessary to note that in Japan tea is also made from shank and thin stems of tea bush. It is called kukicha. Raw materials that are used in the production of skull tea undergo the same treatment as other parts of the plant. Based on the kind of treatment and fermentation, a green or black skull tea is obtained.

Table 3.4 Description of analyzed tea samples from Krasnodar.

СКАЧАТЬ

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Code of a sample	Tea type	Name and origin
A1	Black granulated tea, first grade	Azerchai, “Kuban‐Tea”, Krasnodar region, Belorechensk
A2	Tea black long leaf “Bouquet”
A3	Tea Green Superior Grade, packed
A4	Tea black “Bouquet,” packed
A5	Tea Black Superior Class “Peko”
D1	Tea black skull (petiolar)	Dagomys Chai, Krasnodar region, Sochi
D2	Green long leaf (Bayh) Tea “Extra”
D3	Black long leaf Tea “Extra”
D4	Black long leaf tea № 36
D5	Tea black “Extra” packed
D6	Green tea packed
M1	Tea black classic “Selection” packed	Matcsesta Tea Factory, Matcsesta, Sochi, Izmailovka village
M2	Tea green classic “Selection” packed