Evaluation of the impact of initial red wine composition on changes in color and anthocyanin content during bottle storage

Sixteen commercial red wines, selected to cover a different range of color and total polyphenols index (TPI), were stored at 25 °C during 6 months under controlled and different oxygen additions (0, 1.1, 3.1, 10.6 and 30.4 mg L-1) during the bottling process. Changes in color and the anthocyanic composition were evaluated using transmittance spectra and UPLC-MS-UV/Vis respectively. Results reveal a general pattern in the evolution of wines. However, different patterns of evolution related to initial wine composition, especially to TPI, were observed. Wines with higher TPI had a lower evolution, whereas wines with lower TPI showed a higher evolution and greater variability in behavior. In general, oxygen seemed to accelerate all changes observed during aging although the oxygen effect was more limited than the effect of the storage time. These results are relevant for wine experts and help explain the evolution of wine at the bottling stage

Modelling wine astringency from its chemical composition using machine learning algorithms

Aims: The present work aims to predict sensory astringency from wine chemical composition using machine learning algorithms. Material and results: Moristel grapes from different vineblocks and at different stages of ripening were collected. Eleven different wines were produced in 75 L tanks in triplicate, and further sensory factors were described by the rate-all-that-apply method with a trained panel of participants. The polyphenolic composition was characterised in wines by measuring the concentration and activity of tannins using UHPLC-UV/VIS, the mean degree of polymerisation (mDP. and the composition of tannins using thiolysis followed by UHPLC-MS. Conventional oenological parameters were analysed using FTIR and UV-Vis. Machine learning was applied to build models for predicting a wines astringency from its chemical composition. The best model was obtained using the support vector regressor (radial kernel) algorithm presenting a root-mean-square error (RMSE) value of 0.190. Conclusions: The main variables of the astringency model were the % of procyanidins constituting tannins and ethanol content, followed by other eight variables related to tannin structure and acidity. Significance of the study: These results increase the knowledge of chemical variables related to the perception of wine astringency and provide tools to control and optimise grape and wine production stages to modulate astringency and maximise quality and the consumer appeal of wines

Access to wine experts' long-term memory to decipher an ill-defined sensory concept: The case of green red wine

The present study aims to understand an ill-defined sensory concept by a long-term memory-based strategy with Spanish winemakers from four wine regions using "green wine" as a case study. A total of 77 Spanish winemakers from four Spanish wine regions carried out a non-tasting free description task. The description task yielded terms belonging to two main categories including origin-related terms as well as sensory terms. Sensory terms belonged to aroma, taste, trigeminal, colour, multimodal and hedonic subcategories, which elucidates the multidimensionality of the studied concept. The most cited specific terms were "vegetal aroma", "bitter"and "unpleasant". Despite these commonalities, a certain idiosyncrasy linked to taste ("excessive sourness") and trigeminal ("astringency") subcategories as well as to wine components ("tannins") was evidenced as they were cited distinctly by experts belonging to separate wine regions. The capacity of approaches based on long-term memory to decipher multidimensional and ill-defined concepts is highlighted. The regional effect is also explained in terms of cognitive processes (i.e., knowledge and experience), which is linked to the use of sensory concepts by wine experts

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. © 2002 Elsevier Science B.V. All rights reserved

Assessment of the organoleptic properties of low molecular weight compounds in reconstituted wines

Trabajo presentado en el 9th International Symposium on Viticulture and Enology (ISVE 2015), celebrado en Yangling (China) del 20 al 22 de abril de 2015.Peer Reviewe

Analysis of aged red wine pigments by capillary zone electrophoresis

Red wines of different ages (1-14 years) were analysed by Capillary zone electrophoresis (CZE). Pigments were separated using a fused silica capillary with an effective length of 56 cm and an internal diameter of 75 cm. Disodium tetraborate at 50 mM with a pH of 9.4 was used as buffer solution with methanol as modifier. Electrophoregrams were recorded at 280, 520 and 599 nm and spectra were measured from 200 to 599 nm using a diode array detector. Several differences in the CZE signals obtained for different aged wines were observed, as well as between red and white wines. The signals of a group of seven peaks increased in mature wines. A decrease in free anthocyanins was also identified in aged wine. The migration times of these compounds corresponded to charge/size ratios higher than those of free anthocyanins, and their spectra suggested combinations of anthocyanins with flavanols or tannins. The global CZE response of these pigmented polyphenolic polymers was linearly correlated with the spectrophotometric determination of polymeric pigments (96%) and age (92%). © 2004 Elsevier B.V. All rights reserved

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)×75 m I.D. fused-silica capillary at 10°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 g/ml of malvidin-3-O-glucoside. The limit of detection and the reproducibility (as a relative standard deviation, n=11) were 1 g/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. © 2002 Elsevier Science B.V. All rights reserved

Role of hydroxycinnamic acids and flavanols in the oxidation and browning of white wines

A study of the changes in phenolic compounds during the oxidation of eight white wines reveals that the content of hydroxycinnamic acids and esters decreases significantly during the process; however, the decrease is seemingly unrelated to the extent of browning of the wine. On the other hand, the flavanol contents of the wines are found to be correlated with the degree of browning at the end of the oxidation process. The behaviors of both types of phenol compound at the two temperatures studied are quite similar

Migration order of wine anthocyanins in capillary zone electrophoresis

Capillary zone electrophoresis (CZE) is an advantageous alternative to liquid chromatography (LC) in the analysis of wine anthocyanins in terms of separation efficiency, analysis time and reagent consumption. Thirteen wine anthocyanins of a Tannat wine, including acylated and non-acylated anthocyanin monoglucosides, pyranoanthocyanins and flavanol derivates, were separated using a 46 cm × 75 m (i.d.) fused-silica capillary and a 50 mM sodium tetraborate buffer of pH 8.4 with 15% (v/v) methanol as modifier. Some of the pigments were isolated by LC fractionation and concentrated by lyophilisation. The reconstituted fractions were analysed by CZE in order to identify the compounds in the electrophoregram and to determine their migration times. The migration order found for the wine anthocyanins is discussed taking into account the molecular charge and mass, and the possibility of complex formation with tetraborate molecules. © 2004 Elsevier B.V. All rights reserved