Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- Chemiomics: network reconstruction and kinetics of Port Wine agingPublication . Monforte, Ana Rita; Jacobson, Dan; Ferreira, A. C. SilvaNetwork reconstruction (NR) has proven to be useful in the detection and visualization of relationships among the compounds present in a Port wine aging data set. This view of the data provides a considerable amount of information with which to understand the kinetic contexts of the molecules represented by peaks in each chromatogram. The aim of this study was to use NR together with the determination of kinetic parameters to extract more information about the mechanisms involved in Port wine aging. The volatile compounds present in samples of Port wines spanning 128 years in age were measured with the use of GC-MS. After chromatogram alignment, a peak matrix was created, and all peak vectors were compared to one another to determine their Pearson correlations over time. A correlation network was created and filtered on the basis of the resulting correlation values. Some nodes in the network were further studied in experiments on Port wines stored under different conditions of oxygen and temperature in order to determine their kinetic parameters. The resulting network can be divided into three main branches. The first branch is related to compounds that do not directly correlate to age, the second branch contains compounds affected by temperature, and the third branch contains compounds associated with oxygen. Compounds clustered in the same branch of the network have similar expression patterns over time as well as the same kinetic order, thus are likely to be dependent on the same technological parameters. Network construction and visualization provides more information with which to understand the probable kinetic contexts of the molecules represented by peaks in each chromatogram. The approach described here is a powerful tool for the study of mechanisms and kinetics in complex systems and should aid in the understanding and monitoring of wine quality.
- Untangling the chemistry of Port wine aging with the use of GC-FID, multivariate statistics, and network reconstructionPublication . Jacobson, Dan; Monforte, Ana Rita; Ferreira, António César SilvaChromatography separates the different components of complex mixtures and generates a fingerprint representing the chemical composition of the sample. The resulting data structure depends on the characteristics of the detector used, univariate for devices such as a flame ionization detector (FID) or multivariate for mass spectroscopy (MS). This study addresses the potential use of a univariate signal for a nontargeted approach to (i) classify samples according to a given process or perturbation, (ii) evaluate the feasibility of developing a screening procedure to select candidates related to the process, and (iii) provide insight into the chemical mechanisms that are affected by the perturbation. To achieve this, it was necessary to use and develop methods for data preprocessing and visualization tools to assist an analytical chemist to view and interpret complex multidimensional data sets. Dichloromethane Port wine extracts were collected using GC-FID; the chromatograms were then aligned with correlation optimized warping (COW) and subsequently analyzed with multivariate statistics (MVA) by principal component analysis (PCA) and partial least-squares regression (PLS-R). Furthermore, wavelets were used for peak calling and alignment refinement, and the resulting matrix was used to perform kinetic network reconstruction via correlation networks and maximum spanning trees. Network-target correlation projections were used to screen for potential chromatographic regions/peaks related to aging mechanisms. Results from PLS between aligned chromatograms and target molecules showed high X to Y correlations of 0.91, 092, and 0.89 with 5-hydroxymethylfurfural (HMF) (Maillard), acetaldehyde (oxidation), and 4,5-dimethyl-(5H)-3-hydroxy-2-furanone, respectively. The context of the correlation (and therefore likely kinetic) relationships among compounds detected by GC-FID and the relationships between target compounds within different regions of the network can be clearly seen.
- Sensory interaction between 3-mercaptohexan-1-ol, 3-isobutyl-2-methoxypyrazine and oxidation-related compoundsPublication . Coetzee, C.; Brand, J.; Emerton, G.; Jacobson, D.; Silva Ferreira, A. C.; Du Toit, W. J.Background and AimsWine aroma is influenced by complex interactions between various wine constituents. This study investigated the sensorial interactive effects of Sauvignon Blanc impact compounds, 3-mercaptohexan-1-ol, 3-isobutyl-2-methoxypyrazine with aldehydes typically originating from oxidation of white wines, methional and phenylacetaldehyde. Methods and ResultsSpiked model wines were subjected to sensory descriptive analysis using a trained panel. The concentration of each compound varied from below aroma threshold value to high values reported in wine. Combinations of the four compounds were also evaluated sensorially. Depending on the concentration of the compounds, methional had a strong suppressive effect on the intensity of attributes contributed by 3-mercaptohexan-1-ol, such as grapefruit and guava, whereas methional and 3-isobutyl-2-methoxypyrazine enhanced the intensity of certain attributes, which included cooked beans and cooked potato. ConclusionsComplex sensory interactions may occur between Sauvignon Blanc impact compounds and compounds related to oxidation depending on concentration of the compounds. Oxidation-derived compounds such as methional can suppress pleasant aroma attributes linked to volatile thiols, while contributing negative attributes especially in the presence of 3-isobutyl-2-methoxypyrazine. Significance of the StudyThis study highlights the importance of preserving fresh and fruity flavours while preventing the formation of unwanted aldehydes due to interactions that can influence the overall aroma profile of the wine. This study may also contribute to the sensory characterisation of oxidised Sauvignon Blanc wine.