Evaluation of aroma enhancement for "Ecolly" dry white wines by mixed inoculation of selected Rhodotorula mucilaginosa and Saccharomyces cerevisiae.

To improve the aroma profile of Ecolly dry white wine, the simultaneous and sequential inoculations of selected Rhodotorula mucilaginosa and Saccharomyces cerevisiae were performed in wine making of this work. The two yeasts were mixed in various ratios for making the mixed inoculum. The amount of volatiles and aroma characteristics were determined the following year. Mixed fermentation improved both the varietal and fermentative aroma compound composition, especially that of (Z)-3-hexene-1-ol, nerol oxide, certain acetates and ethyls group compounds. Citrus, sweet fruit, acid fruit, berry, and floral aroma traits were enhanced by mixed fermentation; however, an animal note was introduced upon using higher amounts of R. mucilaginosa. Aroma traits were regressed with volatiles as observed by the partial least-square regression method. Analysis of correlation coefficients revealed that the aroma traits were the multiple interactions of volatile compounds, with the fermentative volatiles having more impact on aroma than varietal compounds.

A novel spectral fingerprint analysis to discriminate dry red wines.

A novel spectral fingerprint to discriminate different dry red wines was built using data visualization method. Twelve red wines with different vintages, cultivars and ageing methods from Changli and Shacheng were sampled. Nine fractions of each wine were collected with a reversed-phase C18 column, and then they were lyophilized. The residue of each fraction was resolved with synthetic wine of the same volume with the fraction sample. The transmittance spectra of wines and their fractions were recorded from 190 to 1100 nm. And the spectral data were visualized to show their visual differences directly. Mono-phenols in wine and fractions were analyzed by HPLC-DAD at wavelengths in the range where located the obvious differences of the spectral fingerprints. The results showed that the spectral differences of wine samples lied in the range of 190 to 600 nm. There were obvious differences in visual maps among wines with different vintages, mainly around 520 nm. The visualization differences among wines with distinct geographical origins lay in the F8 maps, and the differences from the aging methods almost cover the whole wavelength range visualized. However, wines from different grape cultivars had the similar visual characteristics. HPLC-DAD identified the possible monophenol groups for the spectral differences at 280, 313, 365 and 520 nm. It was concluded that the visualization of spectral data from 190 to 600 nm could be used to build red wine spectral fingerprint to distinguish dry red wines with different vintages, origins, and ageing methods.

Contribution of low molecular weight phenols to bitter taste and mouthfeel properties in red wines.

The aim of this study was to explore the relationship between low molecular weight compounds present in wines and their sensory contribution. Six young red wines were fractionated by gel permeation chromatography and subsequently each fraction obtained was separated from sugars and acids by solid phase extraction. Wines and both fractions were in-mouth evaluated by a trained sensory panel and UPLC-MS analyses were performed. The lack of ethanol and proanthocyanidins greatly increased the acidity perceived. The elimination of organic acids enabled the description of the samples, which were evaluated as bitter, persistent and slightly astringent. Coutaric acid and quercetin-3-O-rutinoside appear to be relevant astringent compounds in the absence of proanthocyanidins. Bitter taste was highly correlated with the in-mouth persistence. A significant predictive model for bitter taste was built by means of PLSR. Further research must be carried out to validate the sensory contribution of the compounds involved in bitterness and astringency and to verify the sensory interactions observed.

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.

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.

Characterization of taste-active fractions in red wine combining HPLC fractionation, sensory analysis and ultra performance liquid chromatography coupled with mass spectrometry detection.

Five Tempranillo wines exhibiting marked differences in taste and/or astringency were selected for the study. In each wine the non-volatile extract was obtained by freeze-drying and further liquid extraction in order to eliminate remaining volatile compounds. This extract was fractionated by semipreparative C18-reverse phase-high performance liquid chromatography (C18-RP-HPLC) into nine fractions which were freeze-dried, reconstituted with water and sensory assessed for taste attributes and astringency by a specifically trained sensory panel. Results have shown that wine bitterness and astringency cannot be easily related to the bitter and astringent character of the HPLC fractions, what can be due to the existence of perceptual and physicochemical interactions. While the bitter character of the bitterest fractions may be attributed to some flavonols (myricetin, quercetin and their glycosides) the development of a sensitive UPLC-MS method to quantify astringent compounds present in wines has made it possible to demonstrate that proanthocyanidins monomers, dimers, trimers and tetramers, both galloylated or non-galloylated are not relevant compounds for the perceived astringency of the fractions, while cis-aconitic acid, and secondarily vainillic, and syringic acids and ethyl syringate, are the most important molecules driving astringency in two of the fractions (F5 and F6). The identity of the chemicals responsible for the astringency of the third fraction could be assigned to some proanthocyanidins (higher than the tetramer) capable to precipitate with ovalbumin.

High tolerance of wild Lactobacillus plantarum and Oenococcus oeni strains to lyophilisation and stress environmental conditions of acid pH and ethanol.

A total of 76 Lactobacillus plantarum and Oenococcus oeni wild strains were recovered from traditionally elaborated Spanish red wines and were investigated with respect to their response to acid pH, lyophilisation, temperature and ethanol concentrations which are normally lethal to lactic acid bacteria. Both L. plantarum and O. oeni strains were able to grow at pH 3.2, were highly resistant to lyophilisation treatment and proliferated in the presence of up to 13% ethanol at 18 degrees C. Therefore, it is shown that both species are highly tolerant to stress conditions and that similarly to O. oeni strains, L. plantarum strains are of interest in beverage biotechnology.