Purificación Fernández-Zurbano

Effects of the Nonvolatile Matrix on the Aroma Perception of Wine

Eighteen reconstituted wine samples were prepared by mixing nonvolatile and volatile fractions obtained from six different wines, two whites and four reds, with different characteristics, in an approach that makes it possible to have the same aroma composition in different nonvolatile matrices and vice versa. The aroma elicited by those reconstituted samples was described by a specifically trained sensory panel. Additional gas chromatography-olfactometric and gas chromatography-mass spectrometric studies were carried out to measure differences in aroma release. Results have shown that the nonvolatile matrix of wine exerts a powerful effect on the perception of aroma, strong enough even to make a white wine aroma to smell as a red wine (increasing red, black, and dry fruit notes in detriment of white, yellow, citrus, and tropical) and vice versa and also to create differences in the aroma of reds. It has also been confirmed that the wine nonvolatile matrix exerts a powerful influence on the release of odorants. In particular, headspaces above a white wine matrix are richer in fruity esters and volatile fatty acids. Red wine nonvolatile matrices seem also to retain strongly 3-mercaptohexyl acetate, hence reducing its sensory impact. Comparison of red wine nonvolatile matrices reveals that differences in the retention power of the matrix can affect differentially the pattern of release of linear and branched esters and also of acids.

Modeling quality of premium spanish red wines from gas chromatography-olfactometry data.

The aroma compositions of 25 premium Spanish red wines have been screened by quantitative gas chromatography-olfactometry and have been related to the quality scores of the wines. The study has shown that up to 65 odorants can be present in the aroma profiles of those wines, 32 of which have been detected in less than half of the samples. One new odorant is reported for the first time in wine [(Z)-2-nonenal], and only 11 odorants, most of them weak and infrequent, remain unknown. Quality was not positively correlated with any single compound or with any olfactometric vector built by the summation of odorants with similar odors. However, an olfactometric vector built by the summation of the olfactometric scores of defective odorants, such as 2-methoxy-3,5-dimethylpyrazine, 4-ethylphenol, 3-ethylphenol, 2,4,6-trichloroanisole, and o-cresol was significant and negatively related to quality. Quality could be satisfactorily explained by a simple partial least-squares model (79% explained variance in cross-validation) with just three X-variables: the aforementioned defective vector, a second vector grouping 9 other compounds with negative aroma nuances, and the fruity vector, grouping 15 compounds with fruit-sweet descriptors. This result shows that the quality of these red wines is primarily related to the presence of defective or negative odorants, and secondarily to the presence of a relatively large number of fruit-sweet odorants. Remarkably, only in a few low-quality samples could defective aroma nuances be detected, which suggests that defective and negative odorants exert a strong aroma suppression effect on fruity aroma.

Relationship between Nonvolatile Composition and Sensory Properties of Premium Spanish Red Wines and Their Correlation to Quality Perception

The correlation of nonvolatile composition in wines with quality perception is a critical subject in current enological research, and it is far from being clear. Thus, the present work aims at (1) defining the chemical composition and in-mouth sensory properties of a set of wooded premium Spanish red wines and (2) assessing the implication of their chemical composition in the sensory perception of quality. Therefore, 24 wines were analyzed by sensory descriptive analysis and chemical analysis for nonvolatile composition, and their correlations have been discussed. In parallel, a panel of wine experts performed a quality evaluation based on overall perception. Multivariate statistical analysis has revealed that quality was primarily related to wines without defective aroma and secondarily to the presence of nonvolatile components such as reducing sugars and alcohol content as well as some phenolic compounds: proanthocyanidins linked to polysaccharide, trans-caffeic, trans-coutaric, and trans-caftaric acids, quercetin-3-O-glucuronide, and malvidin-catechin dimer. The results show that wines evaluated as high-quality wines by experts present higher concentrations of these compounds except for trans-caffeic acid, which accumulates higher concentration levels in low-quality wines.

Capillary electrophoretic separation of phenolic diterpenes from rosemary.

The major phenolic diterpenes responsible for the antioxidant properties of rosemary extracts, namely carnosol and carnosic acid, were separated by capillary zone electrophoresis (CZE) using a 56 cm long uncoated fused-silica capillary and a 50 mM disodium tetraborate buffer of pH 10.1. The effect of the buffer type, pH and concentration, and the capillary length on the separation, was studied. Carnosol and carnosic acid were identified in the electrophoregrams of rosemary extracts through their migration times and UV spectra obtained by CZE analysis of pure compounds isolated from a rosemary extract by HPLC fractionation. The CZE method had good reproducibility (relative standard deviation less than 5%) and was applied to compare the contents of carnosol and carnosic acid in solid and oil-dispersed commercial extracts of rosemary and in rosemary leaves. The separation of carnosol and carnosic acid was accomplished in less than 11 min.

Key Changes in Wine Aroma Active Compounds during Bottle Storage of Spanish Red Wines under Different Oxygen Levels

Samples from 16 Spanish red wines have been stored for 6 months at 25 °C under different levels of oxygen (0-56 mg/L). Amino acids, metals, and phenolic compounds were analyzed and related to the production or depletion of key oxidation- and reduction-related aroma compounds. Oxidation brings about sensory-relevant increases in Strecker aldehydes, 1-octen-3-one, and vanillin. Formation of Strecker aldehydes correlates to the wine content on the corresponding amino acid precursor, Zn, and caffeic acid ethyl ester and negatively to some flavonols and anthocyanin derivatives. Formation of most carbonyls correlates to wine-combined SO2, suggesting that part of the increments are the result of the release of aldehydes forming bisulfite combinations once SO2 is oxidized. Methanethiol (MeSH) and dimethylsulfide (DMS), but not H2S levels, increase during storage. MeSH increments correlate to methionine levels and proanthocyanidins and negatively to resveratrol and aluminum. H2S, MeSH, and DMS levels all decreased with oxidation, and for the latter two, there are important effects of Mn and pH, respectively.

Contribution of Nonvolatile Composition to Wine Flavor

This review is aimed at giving an overview of the current state of knowledge of nonvolatile molecules with sensory activity in wine. For this purpose, nonvolatile molecules with known sensory properties are reported and their ability to impact or alter the taste and tactile sensations has been discussed. Then, the importance of sensory interactions in wine is highlighted. Finally, the techniques developed with the aim of detecting nonvolatile sensory-active molecules involved in wine taste or tactile sensations are reviewed. More research should be carried out for determining the real sensory impact of nonvolatiles in global flavor properties; as such, more strategies in both analytical and sensory analyses should be developed. The subsequent steps in relating instrumental data to sensory perception would involve sensory analysis, threshold analysis, and the use of model systems or the addition of a suspected nonvolatile compound with sensory activity directly to the wine.

Development and validation of a capillary zone electrophoresis method for the quantitative determination of anthocyanins in wine

A capillary zone electrophoresis (CZE) method is proposed for the quantitative determination of anthocyanins in wine as an alternative to high-performance liquid chromatography. The CZE separation was carried out using a 46 cm (effective length) x 75 microm I.D. fused-silica capillary at 10 degrees C and a 50 mM sodium tetraborate buffer at pH 8.4 with 15% of methanol as modifier. A voltage of 25 kV and a hydrodynamic injection of 300 mbar s were used. The electropherograms were recorded at 599 nm. It was found that SO2 (antibacterial and antioxidant agent added to wine during its production) increased the absorbance of anthocyanins at 599 nm in a basic medium. Therefore, a concentration of 250 mg/l of SO2 was added to the samples and the calibration solution before the analysis in order to avoid errors by this matrix effect. The analytical response was linear (R=0.998) between 10 and 700 microg/ml of malvidin-3-O-glucoside. The limit of detection and the reproducibility (as a relative standard deviation, n=11) were 1 microg/ml and 1.5%, respectively. Finally, the CZE method was validated by the analysis of synthetic wine samples (errors less than 8%) and by the comparison of the results obtained in the analysis of different monovarietal wines by CZE with those obtained by the standard HPLC method. In this comparison, a good correlation (R=0.998) with a slope of 1.005+/-0.044 and an intercept of -0.752+/-6.690 was obtained for malvidin-3-O-glucoside.

Contribution of non-volatile and aroma fractions to in-mouth sensory properties of red wines: Wine reconstitution strategies and sensory sorting task

This work explores to what extent the aroma or the non-volatile fractions of red wines are responsible for the overall flavor differences perceived in-mouth. For this purpose, 14 samples (4 commercial and 10 reconstituted wines), were sorted by a panel of 30 trained assessors according to their sensory in-mouth similarities. Reconstituted wines were prepared by adding the same volatile fraction (coming from a red wine) to the non-volatile fraction of 10 different red wines showing large differences in perceived astringency. Sorting was performed under three different conditions: (a) no aroma perception: nose-close condition (NA), (b) retronasal aroma perception only (RA), and (c) allowing retro- and involuntary orthonasal aroma perception (ROA). Similarity estimates were derived from the sorting and submitted to multidimensional scaling (MDS) followed by hierarchical cluster analysis (HCA). Results have clearly shown that, globally, aroma perception is not the major driver of the in-mouth sensory perception of red wine, which is undoubtedly primarily driven by the perception of astringency and by the chemical compounds causing it, particularly protein precipitable proanthocyanidins (PAs). However, aroma perception plays a significant role on the perception of sweetness and bitterness. The impact of aroma seems to be more important whenever astringency, total polyphenols and protein precipitable PAs levels are smaller. Results also indicate that when a red-black fruit odor nuance is clearly perceived in conditions in which orthonasal odor perception is allowed, a strong reduction in astringency takes place. Such red-black fruit odor nuance seems to be the result of a specific aroma release pattern as a consequence of the interaction between aroma compounds and the non-volatile matrix.

Insights on the chemical basis of the astringency of Spanish red wines

The main goal of the present study is to provide an insight on the role played by non-volatile molecules on the different in-mouth attributes, particularly astringency. For achieving such goal, the main in-mouth sensory attributes of 34 oaked Spanish red wines were measured by a trained panel. The wine content in 30 sensory-active molecules was analysed by different HPLC based methodologies together with classical enological parameters and two proanthocyanidin indexes. Fourteen compounds (aconitic acids, polymeric proanthocyanidins, caftaric, caffeic and coutaric acids and seven quercetins) were found to be at concentrations above reported taste thresholds and to have a reasonably high range of occurrence. Two highly statistically significant models for astringency were built with those compounds. Even if the models could not be fully validated by sensory addition experiments, the research has demonstrated that wine astringency is driven by polymeric proanthocyanidins and by certain phenolic acids, the rate trans/cis-aconitic acid and flavonol profiles. The research has highlighted the existence of extremely complex interactions between non-volatile compounds on the in-mouth sensory perception. Particularly remarkable is the lack of additivity and potential antagonism found between the pairs cis/trans-aconitic acids, between aconitic and caffeic acids and between quercetin-3-O-galactoside and quercetin-3-O-glucoside. Also remarkable was the sweetness×astringent interaction and the matrix-dependence of the sensory responses elicited by flavonols. These results suggest the need for new paradigms and experimental procedures for fully decoding the real sensory relevance of individual non-volatile compounds in the overall wine flavour.

Taste and Mouthfeel Properties of Red Wines Proanthocyanidins and Their Relation to the Chemical Composition

The aim of this work is to assess the relationship between the in-mouth sensory properties of proanthocyanidins (PAs) and its chemical composition. To achieve such a goal, the proanthocyanidin fraction from six different young commercial red wines was obtained by gel permeation chromatography. A sensory panel, selected on the basis of their PROP status and trained in taste and mouthfeel sensations, described both the wines and fractions. MALDI-TOF-MS and UPLC-MS were used to identify thoroughly the polyphenolic composition of each proanthocyanidin fraction. The results showed that the PAs fractions were exclusively described as astringent and persistent. The astringent subqualities studied (velvety and puckering/drying) were mainly related to the quantity of proanthocyanidins and the proportion of the extension flavanol units linked to proanthocyanidins. A significant negative correlation was found between both of the astringencies (velvety and puckering/drying). Furthermore, both subqualities appeared to contribute to the persistence. A significant correlation was observed between the astringency and the persistence data of the wines and fractions. Significant multiple linear regressions were found between the sensory astringency data and the chemical compounds analyzed. The concentration of proanthocyanidins present in young red wines is the major determinant of the differences perceived in the astringency. Additionally, the extension flavanol units linked to the proanthocyanidins seem to have a different impact on the astringent subqualities.