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Freezing grapes is a winemaking technique known as cryoextraction that intends to modify the composition of the final wines. The changes that take place in the frozen grapes facilitate the transfer of certain compounds from the grape skins into the musts because of the grape&rsquo, s unstructured tissues. For this study, the white grape variety Muscat of Alexandria was selected. Two different cryoextraction procedures have been analyzed as follows: (i) Ultrafast freezing, and (ii) liquid nitrogen freezing. The wines obtained using liquid nitrogen freezing exhibited higher levels of terpenoids, as well as higher levels of hydroxylic compounds and fatty acids than both the wines obtained through traditional methods and ultrafast freezing wines. In any case, both freezing techniques produced wines of a more intense aroma compared with those wines obtained by traditional methods. In fact, liquid nitrogen freezing produced the wines with the most intense aroma and were the best valued by the tasting panel.

Several experiments were conducted to developed orange based vinegar by surface culture. The addition of sugar (sucrose and concentrated must) and the presence/absence of peel in the raw material (squeezed juice, peeled orange, non-peeled orange plus squeezed juice) have been studied during the development of the final product. Polyphenolic and volatile characterization and sensory analysis have also been carried out. The polyphenolic and volatile content of the resulting wines and vinegars showed significant differences depending upon the raw material used. In general, the complexity of the polyphenolic and volatile profiles increased for experiments in which orange peel was included in the raw material. Sensory analysis revealed significant differences between the samples in respect of both sugar addition and raw material. The vinegars using sugar, peeled orange and non-peeled orange plus squeezed juice raw materials, had more preference and keeping in view relative efficiency of the process, vinegar made from the peeled orange material was considered to be best.

Stir bar sorptive extraction (SBSE) has been employed for the analysis of aroma compounds directly from Spanish and Italian grape extracts. The extraction conditions have been optimized using a statistical approach, obtaining results that improve the current state of the art.; Results: The proposed analytical conditions were: sample volume 40 mL, extraction time 80 min, 25% (w/v) NaCl and stirring speed 750 rpm using 20 mm × 0.5 mm stir bars. Performance characteristics of the SBSE procedure were further studied and showed correlation coefficients, detection and quantification limits, linear ranges, recoveries and precision values adequate for analysing these compounds in grapes. Twenty-four grape varieties (aromatic and non-aromatic) were analysed. Statistically significant differences (P < 0.05) according to geographical origin were found, being derived mainly from the terpenoid content. By principal component analysis it was possible to note that the terpenoids were more effective in the separation of the non-aromatic samples, showing negative and positive scores for Italian and Spanish grapes, respectively.; Conclusion: For non-aromatic grape varieties, the factor 'geographic location' was the most significant, thus corroborating the high influence of this parameter on the volatile composition of grapes and therefore on the genuineness of wines. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

Head space sorptive extraction (HSSE) has been evaluated for the analysis of volatile compounds from oak wood in wines. The extraction conditions have been optimized using a two-level factorial design. After optimization, the final extraction conditions were: PDMS stir bars (20 mm length × 0.5 mm film thickness), sample volume of 5 mL, extraction time 120 min, stirring speed 2000 rpm, and NaCl until saturation. The HSSE optimized method was further validated and showed high linearity (r 2 > 0.9960), adequate detection and quantification limits and linear ranges for the analysis of these compounds in aged wines. Moreover, it provided good values of analytical parameters such as precision and recovery (3.49–11.22 % for intra-assay precision, 4.35–8.77 % for inter-assay precision, and 70.6–124 % for recovery). The method was finally applied to different types of fortified wines (Mistelle, Fino and Oloroso wine) from Condado de Huelva Denomination of Origin submitted to different periods of aging in oak wood.

Dietary fiber derived from citrus fruits was added to vinegar. Different sources and quantities of fiber and storage conditions have been scrutinized. Formulated vinegars were evaluated on the basis of their phenolic profile, volatile composition and sensory analysis. The addition of citrus fiber enhanced the phenolic and volatile profile of the resulted vinegars. Whereas lemon fiber contributed mostly to the enrichment of the polyphenolic composition, orange fiber was that which increased in a higher way the volatile composition of the vinegars. Moreover, the content of hydroxycinnamic acid derivatives and the majority of volatile compounds decreased as the dose of fiber increased. Furthermore, the judges preferred fiber-enriched vinegars, but in different quantities depending of the fiber source. This preference was mainly based on citric attribute, contributing several terpenes and ketones derived from them. The addition of citrus fiber to vinegar did not result in a marked storage-dependence.

A fast, simple, and reliable analytical method for the determination of medium-level volatile thiols in wines is presented. Stir bar sorptive extraction using ethylene glycol-silicone coated stir bars has been used in combination with thermal desorption gas chromatography with mass spectrometry for the analysis of 4-mercapto-4-methylpentan-2-one, 2-furanmethanethiol, 3-mercaptohexyl acetate, and 3-mercaptohexanol in wine. Optimization of the extraction technique was performed using a two-level fractional factorial design. For the extraction step, the optimum conditions were: Ethylene glycol and silicone coated stir bars, pH at 3.5, sample volume of 25 mL, extraction time of 90 min, NaCl content 4.0 g, and stirring speed at 500 rpm. The optimized method achieved good linearity for all studied compounds (r2 > 0.995) and it provided detection limits of 21.52, 0.36, 0.73, and 2.55 μg/L for 4-mercapto-4-methylpentan-2-one, 2-furanmethanethiol, 3-mercaptohexyl acetate, and 3-mercaptohexanol, respectively. It was repeatable, with precisions lower than 18% relative standard deviation for both intraday and interday repeatability. The developed procedure is suitable for the determination of these kinds of compounds when they are present at medium concentration levels. It was finally applied to real wine samples with negative aroma derived from the high concentration levels of these compounds.

Several experiments of maceration of a Sherry wine vinegar with different fruits (orange, lemon, strawberry, grapefruit, and lime) have been carried out. After a preliminary study (only peel, no heating and 7 days as maximum time of maceration), parameters such as volatile compounds and sensory characteristics were determined in Sherry wine vinegars macerated with two amounts of peel (100 and 200 g/L) and for two maceration times (3 and 7 days). For volatile compounds, the statistical studies revealed that the factor “fruit” was the most significant with those vinegars obtained from lime, lemon and orange characterized by a high content in terpenic compounds. For those vinegars macerated with orange, high contents in several esters, alcohols, aldehydes and acetates were also observed. The vinegars macerated with strawberry showed very similar volatile profiles to that corresponding to the vinegar without maceration (control vinegar). In the case of the sensory study, the judges (from 12 to 15) preferred different amounts of fruit and maceration time for each fruit. For those vinegars macerated with orange and lime, which were the most preferred by the judges, the best qualifications corresponded to those macerated with the highest amount of fruit.

Stir bar sorptive extraction (SBSE) has been employed for the analysis of aroma compounds directly from Spanish and Italian grape extracts. The extraction conditions have been optimized using a statistical approach, obtaining results that improve the current state of the art.The proposed analytical conditions were: sample volume 40 mL, extraction time 80 min, 25% (w/v) NaCl and stirring speed 750 rpm using 20 mm × 0.5 mm stir bars. Performance characteristics of the SBSE procedure were further studied and showed correlation coefficients, detection and quantification limits, linear ranges, recoveries and precision values adequate for analysing these compounds in grapes. Twenty-four grape varieties (aromatic and non-aromatic) were analysed. Statistically significant differences (P0.05) according to geographical origin were found, being derived mainly from the terpenoid content. By principal component analysis it was possible to note that the terpenoids were more effective in the separation of the non-aromatic samples, showing negative and positive scores for Italian and Spanish grapes, respectively.For non-aromatic grape varieties, the factor 'geographic location' was the most significant, thus corroborating the high influence of this parameter on the volatile composition of grapes and therefore on the genuineness of wines. © 2016 Society of Chemical Industry.

Background Nineteen commercially available aromatised vinegars, which were representative of this type of product, were tested to ascertain their phenolic and volatile composition and antioxidant activity. The aromatised vinegars came from different raw materials such as fruits, spices, herbs and vegetables. The antioxidant activity was determined by means of photochemiluminescence, phenolic profile by using ultra performance liquid chromatography with ultraviolet detection, and the volatile composition was determined by using stir bar sorptive extraction–gas chromatography–mass spectrometry. Results Nine polyphenolic compounds and 141 volatile compounds were identified. Vinegar aromatised with black truffle and rosemary obtained the highest values of antioxidant activity, followed by those aromatised with lemon, tarragon, aromatic herbs and vegetables. Antioxidant activity was highly correlated with the presence of trans-p-coutaric acid, trans-caftaric acid, 5-hydroxy-methylfurfural and furfural. Moreover, (Z)-3-hexen-1-ol was exclusive to the vinegar aromatised with tarragon, while p-menth-1,8-ol, dimethyl styrene, 4-methyl acetophenone and nootkatone were only found in vinegar aromatised with lemon. Conclusion On the basis of the results from the cluster analysis of cases, it can be concluded that the grouping responds more to the trademark of each vinegar than to the raw material.

BACKGROUND: Despite the long history of sherry wine vinegar, new alternatives of consumption are being developed, with the aim of diversifying its market. Several new acetic-based fruit juices have been developed by optimising the amount of sherry wine vinegar added to different fruit juices: apple, peach, orange and pineapple. Once the concentrations of wine vinegar were optimised by an expert panel, the aforementioned new acetic fruit juices were tasted by 86 consumers. Three different aspects were taken into account: habits of consumption of vinegar and fruit juices, gender and age. RESULTS: Based on the sensory analysis, 50 g kg−1 of wine vinegar was the optimal and preferred amount of wine vinegar added to the apple, orange and peach juices, whereas 10 g kg−1 was the favourite for the pineapple fruit. Based on the olfactory and gustatory impression, and ‘purchase intent’, the acetic beverages made from peach and pineapple juices were the most appreciated, followed by apple juice, while those obtained from orange juice were the least preferred by consumers. CONCLUSION: New opportunities for diversification of the oenological market could be possible as a result of the development of this type of new product which can be easily developed by any vinegar or fruit juice maker company. © 2012 Society of Chemical Industry

Aroma compounds of 48 Sherry brandies have been identified and quantified by the stir bar sorptive extraction method coupled to gas chromatography-mass spectrometry (SBSE-GC/MS). Analysis of variance and multivariate analysis techniques have been used to classify these brandy samples according to the commercial category (Solera brandy, Solera Reserva brandy, and Solera Gran Reserva brandy). From an univariate point of view (analysis of variance), several of the volatile compounds considered showed significant differences. Principal component analysis, using the global data matrix, showed that only the Solera brandy samples, with the shortest aging in wood, were well-differentiated from the others. Partial least-squares discriminant analysis (PLS-DA) results provided evidence of the ability of the content of volatile compounds to discriminate among the different commercial categories. Linear discriminate analysis allowed for a 93% differentiation according to the commercial category and, thus, the length of its aging process in wood. The results obtained show that it would be possible to ensure the commercial category of a Sherry brandy using its content of volatile compounds.

Several experiments of maceration of a sherry wine vinegar with different fruits (orange, lemon, strawberry, grapefruit, and lime) have been carried out. After optimization (only peel, no heating and seven days as maximum time of maceration), parameters such as polyphenolic content, superoxide anion scavenging ability (related to antioxidant activity) and ascorbic acid content were determined in sherry wine vinegars macerated with two amounts of peel and for two maceration times (3 and 7 days). The analysis of variance pointed to a clear relationship (p

A study of accelerated aging on an industrial scale, employing both microoxygenation and oak chips, of a Sherry wine vinegar has been carried out. The effect of these two factors, microoxygenation and oak chips, on polyphenolic and volatile compounds, and sensorial parameters has been evaluated. The dose of oxygen applied to the vinegar and the use of chips provoke important changes in its content in polyphenols and volatile compounds and make it similar to the profile obtained using traditional aging. An alternative method of aging is proposed, using 5 g/L of chips and a dose of oxygen around 70 mL/L month. With the proposed method, and according to the sensorial and analytical results obtained, vinegars similar to those traditionally aged can be obtained by accelerated aging with microoxygenation and chips in shorter periods of time. In our case, a final reduction of 86% of time is achieved with the proposed method.

FT-IR calibrations have been made to estimate the aromatic compounds present in vinegars during the acetic fermentation process. A change in the concentration of the major species takes place in this process; ethanol drops from values of around 12% to 10%. To perform these FT-IR calibrations specific zones of the IR spectrum have been employed, which have permitted the calibrations to be validated, with prediction error values below 10% for ethyl esters and higher alcohols, and with errors below 20% for fatty acids. For the case of derivatives of acetic acid and furfurals, the prediction errors in the validation of the method were between 20% and 30%.

BACKGROUND: Due to the diversity of vinegars on the market and the increase in demand, it is considered necessary to investigate and establish criteria for classifying them in order to obtain more information concerning their real origin. New spectroscopic techniques such us mid-infrared spectroscopy with Fourier transform (FT-IR) are capable of providing information in relation to these aspects. FT-IR combined with multivariate analysis has been used to classify vinegars according to the raw materials and production processes (with or without ageing in wood). Principal component analysis (PCA), partial least-squares discriminant analysis regression (PLS-DA) and stepwise linear discriminant analysis (SLDA) were used. RESULTS: The results obtained have been compared to those achieved using different analytical parameters (polyphenolic content, organic acids and volatile compounds). SLDA and PLS-DA results show the ability of mid-FT-IR spectra to discriminate among vinegars from different raw materials and with or without ageing in wood, with correct classification percentages similar to those obtained using different analytical parameters. CONCLUSION: The discriminative ability combined with other advantages (e.g. rapid and non-destructive analysis, low cost) makes this new FT-IR method a promising tool for the classification and/or differentiation of vinegars. Copyright © 2010 Society of Chemical Industry

Aroma compounds are most closely associated with the volatile fraction of foods. Common analytical separation procedures employed to analyse volatile compounds need, even today, that prior to GC analysis of an aroma or a fragrance, these compounds be concentrated or/and isolated from the non-volatile matrix. This step constitutes a problem that has still not been satisfactorily resolved and for this, several sample preparation methods can be found into the bibliography. This review gives a brief overview of solid phase extraction techniques to analyse volatiles. Procedures such as solid phase extraction (SPE), solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), and the recent solid phase dynamic extraction (SPDE) will be discussed and critically evaluated. Contemporary applications of these techniques to the study of volatile compounds in wine and other enological products will be presented.

The characterization of the volatile composition that could have relevance on the organoleptic profile of Andalusian sweet wines obtained from Muscat and Pedro Ximenez grapes has been carried out. Twenty commercial samples, ten from Pedro Ximenez grapes and ten for Muscat grapes, have been studied. Various different chemometric tools have been applied in the analysis of the results. Using Cluster analysis and principal component analysis the samples have been grouped according to grape variety. Linear discriminate analysis allowed a 100% differentiation according to grape variety.

Saccharomyces bayanus var. uvarum plays an important role in the fermentation of red wine from the D.O. Ribera del Duero. This is due to the special organoleptic taste that this yeast gives the wines and their ability to ferment at low temperature. To determine the molecular factors involved in the fermentation process at low temperature, a differential proteomic approach was performed by using 2D-DIGE, comparing, qualitatively and quantitatively, the profiles obtained at 13 and 25°C. A total of 152 protein spots were identified. We detected proteins upregulated at 13°C that were shown to be related to temperature stress, the production of aromatic compounds involved in the metabolism of amino acids, and the production of fusel alcohols and their derivatives, each of which is directly related to the quality of the wines. To check the temperature effects, an aromatic analysis by GC-MS was performed. The proteomic and "aromatomic" results are discussed in relation to the oenological properties of S. bayanus var. uvarum.

Twenty-three monovarietal wines from 13 white and red grapes have been analysed by solid phase extraction–gas chromatography and solid phase micro-extraction–gas chromatography. The content of some varietal terpenic and fermentative volatile compounds was determined. The 13 studied varieties were characterised as well as the influence of winemaking practices like cold soaking and addition of glycosidase enzymes. Terpenic compounds showed a high variability between the 13 varieties which allows for its characterisation. The winemaking practices devoted to increase the aromatic properties of wines produced different results depending on the variety of grape. For example, cold soaking produced very different results if applied on Palomino fino variety or on Traminer variety, whereas for Viura variety few changes were found. Regarding the volatile compounds generated during the alcoholic fermentation, its relative amount is clearly related to the kind of fermentation process carried out, and particularly according to whether maceration of the solid parts has or has not been done during the process. In the case of vinification without maceration, there is a relative increase of fatty acids and their ethyl esters, whereas in vinification with maceration, the ethyl esters of lactic, acetic and succinic acids are the compounds that are relatively more abundant. Additionally, none of these compounds was affected by the techniques applied to increase varietal aroma, i.e. cold soaking, and addition of glycosidase enzymes showed very low influence in the levels of this kind of compounds.

Experiments of accelerated oxidation of “Fino” Sherry wines have been conducted at different temperatures (25 and 45 °C) and under the influence of UV–Vis radiation (a xenon lamp of 1500 W). Two types of glass bottle were employed: topaz bottles (with low values of transmittance in the UV–Vis range) and transparent bottles. To identify significant differences between the wine before and after being subjected to the influence of these factors, the values of absorbance at 420 nm and the concentrations of various polyphenolic and volatile compounds were submitted to a multivariate variance analysis. The three factors “temperature”, “radiation”, and “time” had a statistically significant effect on the values of absorbance at 420 nm and on the concentration of most of the polyphenolic and volatile compounds, while the “bottle” factor was only significant for polyphenol content. All the wines showed losses in several polyphenolic compounds, which were more severe for the wines bottled in transparent glass. The combined application of high temperature and UV–Vis radiation provoked significant decreases in most of the volatile compounds monitored.

Different headspace solid-phase microextraction (HS-SPME) methods have been selected and applied to the analysis of volatile compounds in ‘fino’ sherry wine by gas chromatography-mass spectrometry. A method based on rotary and continuous liquid–liquid extraction (LLE) for analysis of these same compounds has been optimised. The best conditions to extract this type of compounds using SPME and LLE were determined and both methods were validated. Both methodologies show adequate detection and quantitation limits, and linear ranges for correctly analysing these compounds. The recoveries obtained were close to 100%, with good repeatability values. The analytical and procedural advantages and disadvantages of these two methods have been compared. In general, SPME presented higher sensitivities. Both analytical methods were used to analyse five samples of ‘fino’ sherry wine supplied by different producers. No significant differences were found between the techniques at a significance level of 5%. The regression coefficients (r2) for analysis using LLE and SPME exceeded 0.94 for all compounds. The LLE procedure is a method with high repeatability and has the possibility of simultaneous extraction of several samples (up to 12), however the SPME technique is a solvent-free method presenting major advantages, such as small sample volume and higher sensitivity and simplicity.

A study has been conducted of the separation of sugar acids (gluconic, galacturonic and glucuronic acids) by capillary electrophoresis using indirect UV detection. We have tested various background electrolytes: p-hydroxibenzoic acid, sorbic acid, potassium hydrogen phthalate, protocatechuic acid, α-resorcylic acid and β-resorcylic acid. The choice between these electrolytes was made on the basis of studies of electrophoretic mobility and absorbance values at the wavelengths of our CE system. Of all the electrolytes tested, it was found that β-resorcylic acid best met the required characteristics. The best separation of the three acid was achieved with a time of 8 min, for an electrolyte consisting of 5 mM β-resorcylic acid, 1 mM TTAOH (pH 3.0), indirect detection at 214 nm, -20 kV of run voltage and capillary of 60 cm length and 75 µm i.d. It was found that the proposed method is applicable to samples of both must and wine, and that the samples do not require any prior treatment apart from centrifugation (only in the case of must), filtration and dilution in suitable proportion.

Headspace solid-phase microextraction (HS-SPME) was evaluated for analysing aromatic compounds in vinegar. The fibre used (a Carboxen-polydimethylsiloxane fibre), and the analytical conditions had been optimised in a previous work. The HS-SPME procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The recoveries obtained were close to 100%, with repeatability values lower than 20%. However, considerable differences have been detected between different fibres. The method was applied to a variety of Sherry wine vinegars.

A fast, simple, and reliable analytical method for the determination of medium-level volatile thiols in wines is presented. Stir bar sorptive extraction using ethylene glycol-silicone coated stir bars has been used in combination with thermal desorption gas chromatography with mass spectrometry for the analysis of 4-mercapto-4-methylpentan-2-one, 2-furanmethanethiol, 3-mercaptohexyl acetate, and 3-mercaptohexanol in wine. Optimization of the extraction technique was performed using a two-level fractional factorial design. For the extraction step, the optimum conditions were: Ethylene glycol and silicone coated stir bars, pH at 3.5, sample volume of 25 mL, extraction time of 90 min, NaCl content 4.0 g, and stirring speed at 500 rpm. The optimized method achieved good linearity for all studied compounds (r(2)0.995) and it provided detection limits of 21.52, 0.36, 0.73, and 2.55 μg/L for 4-mercapto-4-methylpentan-2-one, 2-furanmethanethiol, 3-mercaptohexyl acetate, and 3-mercaptohexanol, respectively. It was repeatable, with precisions lower than 18% relative standard deviation for both intraday and interday repeatability. The developed procedure is suitable for the determination of these kinds of compounds when they are present at medium concentration levels. It was finally applied to real wine samples with negative aroma derived from the high concentration levels of these compounds.

Nineteen commercially available aromatised vinegars, which were representative of this type of product, were tested to ascertain their phenolic and volatile composition and antioxidant activity. The aromatised vinegars came from different raw materials such as fruits, spices, herbs and vegetables. The antioxidant activity was determined by means of photochemiluminescence, phenolic profile by using ultra performance liquid chromatography with ultraviolet detection, and the volatile composition was determined by using stir bar sorptive extraction-gas chromatography-mass spectrometry.Nine polyphenolic compounds and 141 volatile compounds were identified. Vinegar aromatised with black truffle and rosemary obtained the highest values of antioxidant activity, followed by those aromatised with lemon, tarragon, aromatic herbs and vegetables. Antioxidant activity was highly correlated with the presence of trans-p-coutaric acid, trans-caftaric acid, 5-hydroxy-methylfurfural and furfural. Moreover, (Z)-3-hexen-1-ol was exclusive to the vinegar aromatised with tarragon, while p-menth-1,8-ol, dimethyl styrene, 4-methyl acetophenone and nootkatone were only found in vinegar aromatised with lemon.On the basis of the results from the cluster analysis of cases, it can be concluded that the grouping responds more to the trademark of each vinegar than to the raw material.

A stir bar sorptive extraction gas chromatography–mass spectrometry (SBSE–GC–MS) method has been used for the characterization of the volatile composition of 26 high quality vinegars of three different protected geographical indications (traditional balsamic vinegar of Modena, balsamic vinegar of Modena, and Sherry vinegar). SBSE technique provided the identification of 113 volatile compounds, which belong to different chemical families (short-chain esters, acids, acetates and alcohols, phenols, lactones and benzenic and furanic compounds). 39 volatile compounds were never previously reported in wine vinegars. This characterization contributed to the differentiation of the 100% of the studied samples on the basis of raw material (two different types of wine, and cooked must), aging type (static and dynamic) and aging time (25 years). Furanes and terpenes together with acids and alkanes were the most discriminant variables for raw material and aging time, respectively, whereas for aging type, these ones were acetates and esters.

Due to the diversity of vinegars on the market and the increase in demand, it is considered necessary to investigate and establish criteria for classifying them in order to obtain more information concerning their real origin. New spectroscopic techniques such us mid-infrared spectroscopy with Fourier transform (FT-IR) are capable of providing information in relation to these aspects. FT-IR combined with multivariate analysis has been used to classify vinegars according to the raw materials and production processes (with or without ageing in wood). Principal component analysis (PCA), partial least-squares discriminant analysis regression (PLS-DA) and stepwise linear discriminant analysis (SLDA) were used.The results obtained have been compared to those achieved using different analytical parameters (polyphenolic content, organic acids and volatile compounds). SLDA and PLS-DA results show the ability of mid-FT-IR spectra to discriminate among vinegars from different raw materials and with or without ageing in wood, with correct classification percentages similar to those obtained using different analytical parameters.The discriminative ability combined with other advantages (e.g. rapid and non-destructive analysis, low cost) makes this new FT-IR method a promising tool for the classification and/or differentiation of vinegars.

The volatile composition of 26 premium quality vinegars belonging to three different protected geographical indications (traditional balsamic vinegar of Modena, balsamic vinegar of Modena, and sherry vinegar) has been characterized by means of a solid-phase extraction (SPE) gas chromatography-mass spectrometry GC-MS method. Among the about 90 quantified compounds, short-chain fatty acids, furanic compounds, enolic derivatives, and some esters were found to discriminate the samples as a consequence of differences in the extent of Maillard reactions, presence of alcoholic fermentation, or duration of wood aging.

A solid-phase extraction method for the determination of volatile compounds in traditional balsamic vinegar (TBV) has been developed. The optimisation has been carried out using a two-level factorial design expanded further to a central composite design. LiChrolut-EN SPE cartridges were used and the optimised analytical conditions were: 7 g of TBV diluted 1:4, 5 mL of washing water, and elution with 10 mL of dichloromethane. The linear ranges and detection and quantitation limits were adequate for the analysis of the studied compounds in TBV. The accuracy of the method was also studied: recoveries up to 80% and repeatability values lower than 15% were obtained for the majority of the studied compounds. Two TBVs of different age were analysed by the optimised method.

Stir bar sorptive extraction was evaluated for analysing volatiles in vinegar. The procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The accuracy obtained was close to 100%, with repeatability values lower than 13%. The extraction efficiency is inversely affected by the acetic acid content. Although the absolute areas decrease, the compound area/internal standard area ratio remains constant, so for quantitative analysis, the acetic acid concentration does not affect the analytical data. The method was compared with a previous SPME method. Similar performance characteristics were obtained for both methodologies, with lower detection and quantitation limits and better repeatability reproducibility values for SBSE. Both analytical methods were used to analyse a variety of vinegars. The results obtained from both methods were in agreement.

This paper describes a study of the possibility of obtaining regression models by means of partial least squares (PLS) and multiple linear regression (MLR) that would enable us to correlate a series of parameters, such as the concentration of short-chain organic acids, higher alcohols, and phenolic compounds with the age of vintage Sherry wines or “anadas”. The aim of this study is to characterize how these parameters evolve with aging. If this could be done, it would then be possible to guarantee the age of such wines using objective variables. A PLS regression model was established that allows the age to be predicted with a mean deviation of 1.6 years with respect to the age of the wines. In the case of the MLR, a model with 6 variables was obtained that gives a mean deviation of 3.3 years in the predictions. Keywords: Partial least squares; multiple linear regression; phenolic compounds; volatile compounds; wine; aging

Headspace solid-phase microextraction (HS-SPME) was evaluated for analysing aromatic compounds in vinegar. The fibre used (a Carboxen-polydimethylsiloxane fibre), and the analytical conditions had been optimised in a previous work. The HS-SPME procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The recoveries obtained were close to 100%, with repeatability values lower than 20%. However, considerable differences have been detected between different fibres. The method was applied to a variety of Sherry wine vinegars.

Headspace solid-phase microextraction has been applied to the analysis of aroma compounds in vinegar. Silica fibre coated with Carboxen–polydimethylsiloxane was found to be more efficient at extracting these compounds than other fibres such as those coated with polydimethylsiloxane, Carbowax–divinylbenzene, and polydimethylsiloxane–divinylbenzene, but its repeatability was low. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength, and sample volume were optimised using a two-level factorial design expanded further to a central composite design. This chemometric tool is very appropriate in screening experiments where the aim is to investigate several possibly influential and/or interacting factors. The extraction efficiency is inversely affected by the acetic acid content—an increase in the acetic acid concentration decreases the extraction efficiency. No interference is observed with the increase in content of polyphenols.

Ion-exclusion chromatography (IEC) and capillary electrophoresis (CE) have been compared for determination of organic acids in samples of Sherry wine vinegar. The accuracy of each technique was evaluated by use of the standard addition method. There were no differences between the techniques at a significance level of 5%, except for determination of malic acid by CE. Both analytical methods were used to analyse sixteen samples of Sherry wine vinegar supplied by different producers. The regression coefficients (r2) for analysis by IEC and CE exceeded 0.94 for all acids. Results from both methods were in good agreement and the methods are sufficiently selective and sensitive to be applied directly to sherry wine vinegars.