Composition of three types of honey (mixed forest honey and monofloral-black locust and rapeseed honeys) originated from the vicinity of an industrial town (Košice, Slovak Republic) was compared. Higher content of minerals including toxic metals in forest honey (1358.6 ng Ni/g, 85.6 ng Pb/g, and 52.4 ng Cd/g) than in rapeseed and black locust honeys confirmed that botanical origin rather than the distance for eventual source of pollution (steel factory) affects metal deposition. Benzoic acid derivatives were typically more accumulated in forest but cinnamic acid derivatives and some flavonoids in rapeseed honey (in free and/or glycoside-bound fraction). In terms of quantity, p-hydroxybenzoic and p-coumaric acids were mainly abundant. Total phenols, thiols, and proteins were abundant in forest honey. Some metals and phenols contributed to separation of honeys based on principal component analysis (PCA). Native amount of 5-(hydroxymethyl)furfural was not related to honey type (~11 μg/g) and was elevated after strong acid hydrolysis (200-350 μg/g) but it did not interfere with the assay of phenols by Folin-Ciocalteu reagent. This is the first report of metals and metabolites in the same study, and data are discussed with available literature. We conclude that black locust (acacia) honey is the most suitable for daily use and that central European monofloral honeys contain lower amounts of toxic metals in comparison with other geographical regions.
5-Hydroxymethylfurfural (HMF) was analyzed in 17 botanical varieties of honey from 12 countries. A recently developed high-performance thin-layer chromatographic (HPTLC) method was limited because of increased matrix effects at higher honey sample loading. Therefore, the method was modified to achieve higher sensitivity and eliminate matrix interference by use of rectangular application combined with a focusing step. The HPTLC results were compared with results from the new spectrophotometric Reflectoquant hydroxymethylfurfural assay. Both methods had quantification limits of 4 mg kg(-1) and were suitable for rapid quantification of HMF in honey at the strictest regulated level of 15 mg kg(-1). Comparable results were obtained for the 17 honey samples, with a mean deviation of 2.9 mg kg(-1) (15%). The optimized HPTLC method was proved to be highly matrix-robust and was validated for the 17 different honey matrices (correlation coefficients ≥0.9994 (n = 6), mean intra-day precision 3.2% (n = 3 within a plate; n = 2 repeated within a day), mean inter-day precision 3.7% (n = 3), mean reproducibility over the whole procedure including sample preparation 4.1% (n = 2), and mean recovery 106.9% (n = 5 different concentrations; n = 4 different honey matrices). Recovery for a range of different application volumes, and thus for different honey matrix loading, differed by only ≤4.2%. HMF results when calculated by use of external calibration and by use of the standard addition method varied by 8.8%. Both revealed that any matrix effect was minor and that the original matrix interference problem was successfully solved.
DART (direct analysis in real time), a novel technique with wide potential for rapid screening analysis, coupled with high-resolution time-of-flight mass spectrometry (TOF-MS) has been used for quantitative analysis of 5-hydroxymethylfurfural (5-HMF), a typical temperature marker of food. The DART/TOF-MS method was optimised and validated. Quantification of 5-HMF was achieved by use of a stable isotope-labelled 5-HMF standard prepared from glucose. Formation of 5-HMF from saccharides, a potential source of overestimation of results, was evaluated. Forty-four real samples (honey and caramelised condensed sweetened milk) and 50 model samples of heated honey were analysed. The possibility of using DART for analysis of heated samples of honey was confirmed. HPLC and DART/TOF-MS methods for determination of 5-HMF were compared. The correlation equation between these methods was DART = 1.0287HPLC + 0.21340, R(2) = 0.9557. The DART/TOF-MS method has been proved to enable efficient and rapid determination of 5-HMF in a variety of food matrices, for example honey and caramel.
- MeSH
- 2-furaldehyd analogy a deriváty analýza MeSH
- analýza selhání vybavení MeSH
- design vybavení MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací přístrojové vybavení metody MeSH
- počítačové systémy MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The objective of this study was the determination of 25 phenolic compounds in different mead samples (honeywines) using high performance liquid chromatography (HPLC) with coulometric-array detection and in case of hydroxymethylfurfural with UV detection. Our method was optimized in respect to both the separation selectivity of individual phenolic compounds and the maximum sensitivity with the electrochemical detection. The method development included the optimization of mobile phase composition, the pH value, conditions of the gradient elution and the flow rate using a window-diagram approach. The developed method was used for the determination of limits of detection and limits of quantitation for individual compounds. The linearity of calibration curves, accuracy and precision (intra- and inter-day) at three concentration levels (low, middle and high concentration range) were verified. Mead samples were diluted with the mobile phase at 1:1 to 1:50 ratio depending on the concentration and filtered through a PTFE filter without any other sample pre-treatment. Phenolic compounds concentration was determined in 50 real samples of meads and correlated with meads composition and hydroxymethylfurfural concentration. The most frequently occurred compounds were protocatechuic acid and vanillic acid (both of them were present in 98% samples), the least occurred compounds were (+)-catechin (10% samples) and sinapic acid (12% samples). Vanillin and ethylvanillin, which are used as artificial additives for the taste improvement, were found in 60% and 42% samples, respectively. Hydroxymethylfurfural concentration, as an indicator of honey quality, was in the range from 2.47 to 158 mg/L. Our method is applicable for the determination of 25 phenolic compounds in mead, honey and related natural samples.
- MeSH
- 2-furaldehyd analogy a deriváty analýza chemie MeSH
- fenoly analýza chemie MeSH
- financování organizované MeSH
- molekulární struktura MeSH
- nápoje analýza MeSH
- reprodukovatelnost výsledků MeSH
- spektrofotometrie ultrafialová metody MeSH
- víno analýza MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
