[Show abstract][Hide abstract] ABSTRACT: May bryndza cheese, a type of Slovakian bryndza cheese with a status of Protected Geographical Indication (PGI), produced from raw ewes’ milk, was characterized in one season in 7 specialized factories regarding the diversity of bacteria, yeasts and fungi, and regarding aroma-active volatile compounds. The culture-based microbiological analysis showed that all samples contained high numbers of lactococci, lactobacilli and Galactomyces/Geotrichum. Polymerase chain reaction-based identification classified most of lactobacilli as Lactobacillus paracasei and Lb. plantarum, and most of lactococci as Lactococcus lactis. Culture-independent analysis revealed that the most abundant bacteria were Lactococcus spp. followed by Streptococcus spp. and Leuconostoc spp. The eukaryotic microflora was composed mainly of Galactomyces/Geotrichum, and yeasts Yarrowia lipolytica, Kluyveromyces lactis and Debaryomyces hansenii. Regarding aroma-active volatiles, 28 compounds were detected by gas chromatography-olfactometry with acetic acid, ethyl acetate, 2-methyl-1-propanol, 3-methyl-1-butanol, 2-methyl-1-butanol, 2,3-heptanedione, pentanoic acid and 2,4-dimethyl-1-heptene being present in all samples. Other widely detected compounds were decanoic acid, 3-methylbutanal, butanoic acid, heptanoic acid, tentatively identified 4-octanone, tentatively identified 2,4-dimethyl undecane and tentatively identified 1-dodecanol. The results showed that microbial diversity and principal aroma-active compounds did not markedly differ among individual producers from different geographic regions, which was positive in terms of PGI definition of this cheese.
Journal of food and nutrition research 09/2015; · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Fluorescence spectroscopy provides rapid profiling of food products and could become an effective tool for authentication when coupled to chemometrics. This study developed a simple method for classifying commercial fruit (apple, apricot, pear, and plum) spirits using synchronous fluorescence spectroscopy. Spectra were collected in the excitation wavelength range from 200 to 500 nm, with constant wavelength differences from 10 to 100 nm, and those obtained at wavelength differences 10, 90, and 100 nm were employed in multivariate analysis. Of samples, 100, 90, and 90 % were properly classified by applying the linear discriminate analysis to the first principal components of the principal component analysis performed on the synchronous fluorescence spectra at wavelength differences 10, 90, and 100 nm, respectively. One hundred percent of samples were properly classified by applying the general discriminate analysis to spectra regardless of wavelength difference used. For the comparison, HPLC analysis was also carried out and discrimination models were generated. The best results were obtained with the general discriminate analysis applied directly to the peak area of common HPLC peaks (correct classification 100 %, training set; 95 %, prediction set).
[Show abstract][Hide abstract] ABSTRACT: Nitrate in water samples was determined by in-electrode coulometric titration in porous electrode made of vitreous carbon particles coated with copper. The sample was mixed with diluted sulfuric acid containing 1 mmol/L hydrochloric acid, the solution was filled into the cell and electrode and the nitrate ions were directly reduced by constant current to ammonium ions. The stoichiometry of the electrode reaction was found by coulometric and photometric measurements. The detection limit and precision were found to be 0.2 mg/L and 1.7 %, respectively. The interfering effect of high chloride contents was eliminated by precipitating chlorides with silver sulfate. The method was applied for the analysis of various water samples and beverages. The results were in good agreement with data from isotachophoretic and photometric measurements.
[Show abstract][Hide abstract] ABSTRACT: At present, it is necessary to check the quality of many food products in which the content of coumarins is limited. Since a rapid and simple method for the determination of coumarin (COU), 4-hydroxycoumarin (4HC) and dicoumarol (DC) in tea samples was needed, we developed an alternative option to chromatography, i.e., fluorescence spectroscopy with multivariate calibration. The synchronous fluorescence spectra were recorded at constant wavelength differences 70, 80 and 90 nm from 200 to 400 nm. The different experimental parameters affecting the synchronous fluorescence intensities of the analytes were carefully studied and optimized. Partial least squares (PLS) method and multi linear regression (MLR) were compared on determining the concentrations. The best results were obtained by the PLS method on synchronous fluorescence spectra at Δλ = 90 nm. The results from the analysis of herbal tea Melilotus officinalis by synchronous fluorescence spectroscopy with PLS model are equivalent with the results from HPLC. Fisher F- test and Student's t- test confirmed this finding.
Journal of Fluorescence 01/2015; 25(2). DOI:10.1007/s10895-015-1508-2 · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study introduces a reliable method to detect adulteration of spirit drinks. Excitation-emission matrix (EEM) fluorescence in combination with parallel factor analysis (PARAFAC) and partial least squares (PLS) regression was used to determine the content of water and ethanol in adulterated fruit spirit samples. EEM fluorescence spectra recorded in the emission wavelength range of 315–450 nm and in the excitation wavelength range of 240–305 nm were used for PARAFAC. The model created using PARAFAC-PLS was able to predict the water and ethanol level in adulterated apple spirit with the root mean square error of prediction (RMSEP) values of 1.9 % and 1.8 %, respectively. Regarding adulterated plum spirit, the RMSEP values of 0.7 % and 3.5 % were obtained for water and ethanol, respectively. The aim of this work was to determine whether EEM-PARAFAC can be used to distinguish between plum and apple spirit. Better results were obtained for apple spirit and the method is useful also for water-apple spirit blends.
[Show abstract][Hide abstract] ABSTRACT: The aim of this work was to develop a multivariate method for the rapid determination of caffeine and Class IV caramel in cola-type soft drinks and of caffeine, Class III caramel and riboflavin in energy drinks using synchronous fluorescence spectra. The synchronous fluorescence spectra were recorded at constant wavelength difference 90 nm from 200 to 500 nm. Reference values of analyte concentrations by high performance liquid chromatography (HPLC) with fluorescence detection combined with the standard addition method were used to create the partial least squares (PLS) models. High coefficients of determination (>0.99) were obtained in 0.2–4.2, 0.25–5.25, 0.4–10.0 and 0.007–0.054 mg L−1 range for caffeine, Class III caramel, Class IV caramel and riboflavin, respectively. The PLS models were used to determine the concentration of analytes in different drink samples. The method provided comparable results with those found using the HPLC method.
[Show abstract][Hide abstract] ABSTRACT: The addition of mixed wine spirit to brandy is easy way to adulterate brandy. To avoid the misleading of the consumers, it is necessary to develop reliable method to detect adulteration of brandy. In this work excitation emission matrix fluorescence in combination with parallel factor analysis (PARAFAC) and partial least squares (PLS) regression was used to determine the content of mixed wine spirit in adulterated brandy samples. Excitation emission matrix fluorescence spectra were measured in the emission wavelength range of 485–580 nm and in the excitation wavelength range of 363–475 nm. The model created using PARAFAC–PLS was able to predict the mixed wine spirit level in adulterated brandy with the root mean square error of prediction (RMSEP) value of 1.9% and a square of the correlation (R2) between the reference contents and the predicted values of 0.995.
[Show abstract][Hide abstract] ABSTRACT: Volatile aroma compounds were investigated along the production of May Bryndza cheese, a traditional Slovakian cheese produced from raw ewes’ milk. Solid phase microextraction was used to isolate the volatile fractions, which were subsequently analysed by gas chromatography–olfactometry and gas chromatography–mass spectrometry. Twenty-seven key odorants were found and described in the intermediate product, ewes’ curd ripened for 0, 1, 2, 4, and 8 days, or in the final product. A major overall increase in the number of aroma-active volatile compounds and in their odour intensity or concentration took place during the first day of ripening of the ewes’ curd, and the odour gradually culminated at the end of ripening. During the final technological step of Bryndza cheese production, when the ewes’ curd ripened for 10 days is decrusted, pressed and milled with NaCl solution, 8 aroma-active volatile compounds disappeared.
[Show abstract][Hide abstract] ABSTRACT: Brandy, a spirit drink produced from wine (grape), is rich in phenolic acids due to its maturation in wooden barrels. Phenolic acids play a significant role in defining the sensorial characteristics of wines and brandies, and therefore, it is very useful to determine them. Synchronous fluorescence spectra of mixtures containing phenolic acids (gallic, vanillic, syringic and ferulic) and scopoletin have been used for the determination of these compounds by partial least squares (PLS)2. Synchronous fluorescence spectra were collected by simultaneously scanning the excitation and emission monochromator in the excitation wavelength range 200–500 nm, with constant wavelength difference 100 nm between them. The leave-one-out cross-validation method was used to select the optimum number of five PLS2 components (latent variables). The PLS2 model captured for 100 % of variance in the spectral block, and it accounted for 99.34 % of variance in the concentration block. The performance of the model was evaluated by means of root mean square error of cross-validation, root mean square error of prediction and coefficient of determination. The best model was used for the determination of the above-mentioned compounds in brandy samples at concentration levels 2–74 mg L−1 for phenolic acids and 0.06–0.43 mg L−1 for scopoletin. The PLS2 results were found to be in good agreement with those obtained by HPLC method.
[Show abstract][Hide abstract] ABSTRACT: The addition of water or ethanol to brandy is an easy way to adulterate brandy. To avoid the misleading of consumers, it is necessary to develop a reliable method to detect the adulteration of brandy. In this work excitation-emission matrix fluorescence in combination with parallel factor analysis (PARAFAC) and partial least squares (PLS) regression was used to determine the content of water, ethanol and methanol in adulterated brandy samples. Excitation-emission matrix fluorescence spectra were measured in the emission wavelength range of 510-600 nm and in the excitation wavelength range of 393-497 nm. The model created using PARAFAC-PLS was able to predict the water, ethanol and methanol level in adulterated brandy with root mean square error of prediction values of 0.24%, 0.20% and 0.22%,respectively, and coefficients of determination of prediction between the reference content and the predicted values of 0.993, 0.997 and 0.995, respectively.
[Show abstract][Hide abstract] ABSTRACT: This study compares the use of UV absorption, excitation–emission matrix (EEM) fluorescence and synchronous fluorescence spectroscopy and HPLC with fluorescence detection combined with principal component analysis (PCA), parallel factor analysis (PARAFAC) and linear discriminant analysis (LDA) for distinguishing between commercial samples of Slovak, Belgian, German, Czech and British juniper-flavoured spirit drinks. Overall, 97 %, 88 % and 79 % of samples were properly classified by applying the LDA to the first five principal components of the PCA performed on the synchronous fluorescence spectra (constant wavelength difference 10 nm, 250–450 nm), UV absorption spectra (250–325 nm) and the areas of eight common HPLC peaks, respectively. EEM fluorescence spectroscopy could not discriminate British drinks, while HPLC failed to discriminate Belgian samples. When the areas of eight common HPLC peaks were used as model parameters instead of the five PCs initially used in LDA, the method accuracy was enhanced significantly and 97 % of predicting samples were properly classified.
[Show abstract][Hide abstract] ABSTRACT: 7-R-9-ethyl-6,9-dihydro-6-oxo-[1,2,5]selenadiazolo[3,4-h]quinolines (R =H, COOC2H5, COOCH3, COOH and COCH3, E1h–E5h) and 6-ethyl-6,9-dihydro-9-oxo-[1,2,5]selenadiazolo[3,4-f]quinoline (E1f) were characterized by UV/vis, FT-IR and fluorescence spectroscopy. The electronic absorption spectra of the derivatives E1h–E3h and E5h in
the aprotic solvents dimethylsulfoxide (DMSO) and acetonitrile (ACN) reveal low-energy absorption maxima with lmax>400> nm, shifted hypsochromically in water. In DMSO, N-ethyl selenadiazoloquinolones behave as strong fluorescent agents (lem ≥ 550 nm) with the exception of the carboxylic acid derivative E4h which shows only poor emission. Photoinduced reactions of N-ethyl selenadiazoloquinolones were investigated by means of electron paramagnetic resonance (EPR) spectroscopy. Photoexcitation of N-ethyl selenadiazoloquinolones in aerated DMSO with either 385 nm or 400 nm wavelengths, monitored by EPR spin trapping technique, results in the generation of superoxide radical anions; under an inert atmosphere, the generation of methyl radicals originating from the solvent predominates. Upon exposure at either 365 nm, 385 nm or 400 nm, aerated ACN solutions of selenadiazoloquinolones in the presence of sterically hindered amines produce nitroxide radicals via a reaction with photogenerated singlet oxygen. The 7-substituted derivatives of 9-ethyl-6,9-dihydro-6-oxo-[1,2,5]selenadiazolo[3,4-h] quinoline behave as photosensitizers activating molecular oxygen upon photoexcitation and possess the sufficient photochemical stability under the given experimental conditions. The cytotoxic effects of non-photoactivated and UVA photoactivated N-ethyl substituted selenadiazoloquinolones on cancer (human HeLa and murine L1210) and non-cancer (NIH-3T3) cell lines were monitored by the MTT test. The derivative E2h demonstrates the highest cytotoxic/photocytotoxic activity on the neoplastic cell lines.
[Show abstract][Hide abstract] ABSTRACT: Two spectrofluorimetric methods have been developed for the rapid determination of ellagic acid. The first method is based on the complex formation between ellagic acid and borax in methanol solution. The fluorescence of the complex is monitored at an emission wavelength of 456nm with excitation at 383nm. Linear calibration curve was obtained from 2.5×10(-8) to 7.5×10(-7)molL(-1) and the limit of determination was 4×10(-9)molL(-1). The second method is based on the complex formation between ellagic acid and boric acid in ethanol solution. The fluorescence of the complex is monitored at an emission wavelength of 447nm with excitation at 387nm. Linear calibration curve was obtained from 1.25×10(-7) to 1.00×10(-6)molL(-1) and the limit of determination was 7×10(-9)molL(-1). The methods were successfully applied for the determination of ellagic acid in brandy samples. The results were found to be in good agreement with those obtained by HPLC method.
[Show abstract][Hide abstract] ABSTRACT: This paper illustrates the composition of propolis samples obtained from two regions in the Slovak Republic and focuses on the determination of coumarins. The HPLC method with on-line spectrophotometric and fluorescent detection was used for the separation and the determination of coumarins from the subgroup of simple coumarins (esculin, daphnetin, fraxetin, umbelliferone, 4-methylumbelliferone, 4-hydroxycoumarin, scoparone, coumarin, herniarin) and cinnamyl alcohol. The results confirmed that the quantity of umbelliferone, 4-methylumbelliferone and scoparone in the propolis depends on the area of collection. The HPLC results were compared with those obtained by the spectrofluorimetric method developed for the determination of total coumarins (calculated as scoparone). For the quantification of total coumarins in propolis extracts we found 15% higher values of coumarin content by fluorescence spectrometry than by HPLC, which can be ascribed to the higher matrix effects on fluorescence spectra.
Journal of Liquid Chromatography & Related Technologies 01/2012; 36(4). DOI:10.1080/10826076.2012.660724 · 0.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this research is to develop a fluorescence spectroscopic method for distinguishing between brandies aged in oak
casks and non-aged caramel-colored mixed wine spirits, and subsequent determining of caramel in the latter. Owing to the low
price of the mixed wine spirits, they are sometimes used for the counterfeiting brandies. For this reason, there is a need
to establish a rapid method for estimation of drink quality to reassure consumer. The potential of synchronous fluorescence
spectroscopy is demonstrated to differentiate caramel from oak wood extract, while the best discrimination is achieved using
fluorescence spectra recorded at Δλ=40nm. For this offset value, oak wood extract shows band at 280nm and caramel shows band at 387nm. Based on this, caramel
quantity in non-aged mixed wine spirits was calculated from fluorescence intensity at 387nm. The calibration curve was linear
over the range from 5 to 56mg/L and the limit of determination was 5mg/L. The relative standard deviation was <4% (within-day)
and it was <6% (between-day) at 10 or 30mg/L level.
European Food Research and Technology 03/2010; 230(5):797-802. DOI:10.1007/s00217-010-1221-y · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t This study demonstrates the use of front face fluorescence spectroscopy and multivariate data analysis for differentiating brandies from wine distillates. Owing to the low price of the wine distillates, they are sometimes used for the counterfeiting brandies. For this reason, there is a need for a rapid method for drink authentication to reassure consumers and protect regional designations. Total luminescence and synchronous scanning fluorescence spectra were recorded followed by a classification of samples using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Both PCA and HCA carried out on the emission spectra (360–650 nm) recorded at excitation wavelength 350 nm and syn-chronous fluorescence spectra (200–700 nm) collected at wavelength interval 90 nm provide very good differentiation between the two spirit classes. Less good classification was obtained using excitation spectra (225–425 nm) obtained at emission wavelength 440 nm. These results indicate that the front face fluorescence spectroscopy offers a promising approach for the authentication of brandies.