The high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) was optimized for the simultaneous determination of 11 compounds, belonging to polyphenols (gallic acid and ...seven catechins) and methylxanthines (caffeine, theobromine, and theophylline). The results obtained for all the validation parameters of the HPLC-DAD method showed that the method is sensitive enough for routine analysis with basic chromatographic equipment, thus it has a significant potential to be highly applicable in common laboratory practice. The method was used in the analysis of 60 green tea infusions originating from four tea-producing countries. The dataset contributes to enhancing current data on green tea. The analysis of green tea extracts revealed significant differences depending on the origin of the samples. Linear Discriminant Analysis (LDA) was applied to test the accuracy of identification of the origin of the tea samples, based on the chemical composition of tea with a focus on polyphenolic compounds and methylxanthines analysed in this study. Based on cross-validation results, the model showed 93.75 % accuracy in the classification of green tea originating from Japan, China (Mainland), China (Taiwan) and South Korea.
•The new HPLC method for 8 tea polyphenols and 3 methylxanthines determination.•The method validation and evaluation of its applicability for the routine use.•The method application on the analysis of 60 green tea samples from four regions.•The LDA model for green tea classification based on chemical composition.
In recent years, the use of natural preservatives in food products has gained significant attention due to their potential health benefits and effectiveness. A standardized microbiological analysis ...was conducted on Slovak farm-produced lump goat cheese samples to determine the antibacterial activity of dry herbs and essential oils added to vacuum-packed goat cheese. We employed five dried herbs and five essential oils derived from the same plants. The microbiological quality of 145 fresh and vacuum-packed goat cheese samples was assessed. The number of coliform bacteria, total viable count, lactic acid bacteria, and microscopic filamentous fungi were examined in raw cheese samples stored for 12 days at 4 °C. All cheese samples were vacuum-packed (control samples were packed without vacuum). This study evaluated the potential benefits of using essential oils and dried herbs from thyme (Thymus serpyllum L.), black pepper (Piper nigrum L.), clove (Eugenia caryophyllus Thunb.), mint (Mentha × piperita L.), and basil (Ocimum basilicum L.) as preservatives. The essential oils were obtained from Hanus Ltd., Nitra, Slovakia, and were applied at a concentration of 2%. The dried herbs were obtained from Popradský čaj (Poprad, Slovakia) and Mäspoma Ltd. (Zvolen, Slovakia). The results showed that all microorganism groups were significantly reduced in cheese samples following the application of essential oils throughout the entire storage period. During the preservation of cheese samples in polyethylene bags used for vacuum packing food, Lactococcus garvieae, L. lactis, Enterobacter cloacae, and Serratia liquefaciens were the most frequently isolated microbiota. Essential oils and dried herbs demonstrated antimicrobial potential during the storage of vacuum-packed goat cheese.
A rapid sampling technique for the analysis of beer aroma compounds is described. The headspace (10
ml) is passed through the microcolumn filled with 5
mg of Tenax TA and thermally desorbed in a ...modified GC inlet (modification is described). Eight compounds (from acetaldehyde to 2-phenylethanol) in four beer samples were analyzed. The correlation coefficients (
r
2), repeatability (RSD) and limits of detection (LOD) were 0.9973–0.9994, 2.1–6.9% and 0.00002–0.13
mg/l, respectively. The methodology can be useful for routine beer sample analysis.
The study is focused on investigation of Slovakian and Bulgarian wines
on the other hand, they contained more alcohols. Compared to samples of the Slovakian wines, significantly higher levels of ...1-butanol were detected in Bulgarian Riesling. On the other hand, Slovakian Riesling and Sauvignon Blanc wines had on average twice the concentration of ethyl butanoate in comparison with respective Bulgarian wines. Based on radar charts, which were created using data of quantitative assessment of selected aromatic compounds, the highest score demonstrated in all the samples of Slovakian and Bulgarian wines was that of “pineapple” note. The pear, banana and acid notes were also typical for Slovakian wines, while the corresponding Bulgarian wines were mostly characterized by acid note
their production, basic parameters, as well as assessment of selected higher alcohols and esters. Bulgarian wines – Chardonnay, Riesling, Cabernet Sauvignon and Sauvignon Blanc (2008–2010 vintages) were prepared. Their features were compared with those of Slovakian wines of the same vintage years and grape variety. Much lower concentrations of esters were detected in Bulgarian wines in comparison with the Slovakian wines
pear and banana notes were minor, or they were absent. Results of analyses were confirmed by a degustation commission.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract
The in vitro cell cultures of Vitis vinifera L. cv. St. Laurent were treated with two elicitors - synthetic methyl jasmonate and natural, prepared from grapevine plant infected with the ...Phaeomoniella chlamydospora, the agent causing the Esca disease of grapevine. Efficiency of phenolic compounds production after elicitation of cell culture was analysed immediately after treatment (15 min, 30 min, 60 min) and later (after 24, 48, and 72 hours). The cell growth and content of phenolic compounds (+)-catechin, (-)-epicatechin, p-coumaric acid, syringaldehyde, rutin, vanillic acid, and trans-resveratrol were analysed in cultivated cells as well as in cultivation medium. Pch-treatment increased production of total polyphenols the most significantly 15 min after the elicitation and in optimal time was 2.86 times higher than in nonelicited culture and 1.44 times higher than in MeJa induced cell culture.
Due to their low dead volumes, microcolumns with Tenax TA coupled to a capillary column in the modified GC inlet allow analysis of a broad range of compounds (from acetaldehyde to 2-phenylethanol) in ...a single sample run. In this study, a microcolumn was filled with 10 mg of Tenax TA. Chromatograms showed well-resolved peaks even at the beginning of the run. Static headspace was used to pre-concentrate the compounds. The method is rapid, simple and inexpensive.
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