Organic Acids In Wine Research Articles

Determination of Organic Acids in Red Wine and Must on Only One RP-LC-Column Directly After Sample Dilution and Filtration

A new method for simultaneous determination of organic acids in red wine and must by liquid chromatography was studied. The determination of organic acids in wines can be achieved in less than 13 min, preceded only by a simple sample dilution and filtration step. With this method, the chromatographic separation of eight organic acids and interfering peaks present in red wine, required only one reversed phase column (Waters Atlantis dC18 column, 4.6 × 150 mm ID, 5 μm). As mobile phase, isocratic acetonitrile–0.01 mol L−1 KH2PO4 at pH 2.7 5:95 (v/v) at a flow rate of 0.8 mL min−1 was used. Detection wavelength was set at 210 nm except for ascorbic acid which was detected at 243 nm. Application to red wine and must confirmed good repeatability and showed a wide variation range for concentrations of organic acids.

Flow injection on-line dialysis coupled to high performance liquid chromatography for the determination of some organic acids in wine

A combined system of flow injection on-line dialysis sample pretreatment and high performance liquid chromatographic separation/detection (FID–HPLC) was developed for simultaneous determination of six organic acids (tartaric, malic, lactic, acetic, citric and succinic acids). A sample or mixed standard solution (400 μL) was injected into a donor stream (water) of FID system and was pushed further through a dialysis cell, while an acceptor solution (water) was held in the opposite side of the dialysis membrane. The dialysate containing organic acids in the acceptor solution was then flowed to an injection loop of the HPLC valve, where it was further injected into the HPLC system and analysed under normal HPLC conditions, using a reversed-phase (C 18) analytical column and UV detection (210 nm). The order of elution was tartaric, malic, lactic, acetic, citric and succinic acids with the analysis time of 8 min. The FID system could be operated in parallel with HPLC separation, providing sample throughput of 7.5 h −1. Dialysis efficiencies of six organic acids were in range of 4.6–9.5%. Calibration graphs for all the mentioned organic acids were linear over the range of 250–7500 mg L −1. Precisions for all the organic acids were within 5.4%. The proposed system was successfully applied for analysis of some Thai wines. By spiking wine samples with mixed acid standard solutions, the percentage recoveries in range of 84–104 were found. This system has advantages of fast and high degrees of automation for dialysis sample pretreatment, on-line sample separation and dilution, good clean-up for prolongation of life-time of the HPLC column and low consumption of chemicals and materials.

Rapid method for the determination of organic acids in wine by capillary electrophoresis with indirect UV detection

A capillary electrophoresis method for organic acids in wine was developed and validated. The optimal electrolyte consisted of 10 mmol/L 3,5-dinitrobenzoic acid (DNB) at pH 3.6 containing 0.2 mmol/L cetyltrimethylammonium bromide as flow reverser. DNB was chosen because it has an effective mobility similar to the organic acids under investigation, good buffering capacity at pH 3.6, and good chromophoric characteristics for indirect UV-absorbance detection at 254 nm. Sample preparation involved dilution and filtration. The method showed good performance characteristics: Linearity at 6 to 285 mg/L ( r > 0.99); detection and quantification limits of 0.64 to 1.55 and 2.12 to 5.15 mg/L, respectively; separation time of less than 5.5 min. Coefficients of variation for ten injections were less than 5% and recoveries varied from 95% to 102%. Application to 23 samples of Brazilian wine confirmed good repeatability and demonstrated wide variation in the organic acid concentrations.

Capillary zone electrophoresis of organic acids in beverages

Capillary zone electrophoresis (CZE) with photodiode array detection (PDA) was applied to simultaneously determine eleven organic acids in wine, beer, and fruit and vegetable juices after derivatisation with 2-nitrophenylhydrazine (2-NPH) in the presence of N-(3-dimethylaminopropyl)- N′-ethylcarbodiimide hydrochloride (EDC·HCl). The parameters affecting CZE separation included type and concentration of buffer, pH, organic additive and applied voltage. Optimum conditions at 25 °C were: 30 mmol l −1 borate buffer, pH 10.0, containing 100 ml l −1 acetonitrile, at 20 kV, sample injection at 0.5 psi for 5 s, with direct detection at 230 nm. Separation of eleven organic acids was achieved within 12 min. Linear calibration curves with good fit were obtained in the range 10.0–100.0 mg l −1. Limits of detection ranged from 2.0 to 10.0 mg l −1. Intra-day precision with RSD⩽4.0% for migration time and ⩽5.0% for peak area, and inter-day precision with RSD⩽6.0% and ⩽9.0% for migration time and peak area, were obtained. Recovery for all beverage samples was 97±15%.

Novel approach for the rapid determination of water‐soluble organic acids in wine by co‐electroosmotic flow capillary zone electrophoresis

An innovative protocol for the fast analysis of some organic acids in red wine by co-electroosmotic capillary zone electrophoresis and indirect UV detection using hexadimethrine bromide (HDB) as coating agent was proposed. The adsorption of HDB onto the capillary wall provided a stable electroosmotic flow and separation of small anions was carried out using background electrolytes containing no polymer additive. Low RSD% values (<3.6%) in terms of migration times and effective mobilities were obtained from the analysis of a mixture of nitrate and nitrite and of a mixture of organic acids. An experimental design approach was used to investigate the effects of temperature, separation voltage, and percentage of methanol added to the running buffer solution on the separation of the analytes. A faster method allowing the separation of the organic acids involved in the malolactic fermentation of wine was developed. Using a running electrolyte consisting of 35% (v/v) methanol in a solution of 22 mM benzoic acid at pH 6.10 adjusted with 1.0 M TRIS-base buffer, the separation of tartaric, malic, succinic, acetic, and lactic acids was feasible in less than 210 s. Application of the method to the quantification of the above-mentioned organic acids in Italian red wine samples is reported.

Determination of organic acids in wine by zone electrophoresis on a chip with conductivity detection

An appropriate combination of separation mechanisms (simultaneous use of differences in pK values, host-guest complexations, and the ionic strength dependences of the actual ionic mobilities) provided zone electrophoresis (ZE) resolution of 22 organic and inorganic acids expected in wines on a polymethylmethacrylate (PMMA) chip with integrated conductivity detection. These separating conditions offered a framework for the ZE determination of organic acids responsible for some important organoleptic characteristics of wines (tartrate, malate, succinate, acetate, citrate, and lactate). The ZE procedure developed in this context is simple and rapid (ca. 10 minutes' analysis time), while affording reproducible migration and quantitation data for the acids. For example, 0.8-2.0% RSD values characterized the migration times of the acids for 25 repeated ZE runs with the same sample carried out in 5 days in the background electrolyte solution prepared freshly on a daily basis, while 3-5% RSD values were typical for the accompanying peak area data. The concentration ranges within which the acids of analytical interest could be determined in one ZE run covered all wine samples included in our study (100-400-fold sample dilutions were needed to work under the conditions corresponding to the validities of the calibration data). 90-110% recoveries of the acids as obtained repeatedly for one of the reference wine samples used in our experiments indicate a good predisposition of the present method to provide accurate analytical results. This statement also supports the results from the determination of the acids in reference wine samples with claimed concentrations of malic (five samples), tartaric (one sample), and lactic (one sample) acids.

Analysis of organic acids in wines by Fourier-transform infrared spectroscopy

Fourier-transform infrared (FTIR) spectroscopy has been a major point of development in many wine laboratories in recent years. It enables almost instant analysis of several properties of wine, usually with very good precision and accurate results. Nevertheless, validation procedures should not be forgotten and should be fully performed. Recovery experiments were performed by spiking wine samples with different amounts of organic acids (tartaric, malic, lactic, acetic and citric--the most prominent in wines). After FTIR analysis of the total acidity and of each organic acid concentration, recoveries were calculated. For total acidity recovery results were, in general, good and very close to 100% (64-111%). On the other hand, for individual organic acid concentrations, the recovery results were lower than 100% (11-73%) for all spiking additions. These results could be explained by spectroscopic interferences between the organic acids. Because they have similar infrared spectra, it is not easy to distinguish between them and, therefore, to achieve accurate calibration. When total acidity, with a different infrared spectrum from the other abundant compounds in the wine, was taken as a single property the recovery results were acceptable.

Method Development for the Determination of Seven Organic Acids in Wines by Reversed-Phase High Performance Liquid Chromatography

A simple high performance liquid chromatographic method is described for the determination of seven organic acids usually found in wines. The acids were eluted in the isocratic mode, in less than 12 min, on a reversed-phase ODS-2 (250 × 4 mm I.D.), 5 μm, column with 0.02 M potassium dihydrogen phosphate (pH 2.88), to which was added a small amount of methanol (2%) as organic modifier, and were detected by ultraviolet absorbance at 230 nm. Galacturonic, tartaric, malic (both enantiomers), lactic, acetic, citric and succinic acids were determined, using xanthine as a chromatographic internal standard. The method was applied to white and red wines of Greek origin, after sample clean-up with polyvinylpyrrolidone, followed by passage through SAX cartridges and yielded recoveries from 78.0 to 106.8%. The limits of detection ranged between 0.001–0.05 g.L−1 and the linear ranges between 0.003–2.0 g.L−1.

A robust capillary electrophoresis method for the determination of organic acids in wines

A robust capillary electrophoresis (CE) method for the determination of the six main organic acids in wines is described. The CE method is based on the use of 2,6- pyridinedicarboxylic acid (PDC) as background electrolyte (BGE) for the indirect UV detection of tartaric, malic, citric, succinic, acetic and lactic acids. Ethylenediaminetetracarboxylic acid (EDTA) was added to the BGE to eliminate interferences from trace metals on the determination of citric acid. Problems related to linearity reported in the literature using the same BGE were shown to be the result of the sample pH being lower than that of the buffer. Although this could be overcome simply by adjusting the pH of the sample, electrokinetic injection was found to be a better alternative, improving at the same time the sensitivity of the determination. Linearity over the range 100–5,000 mg/l (ppm) for all acids was achieved, requiring only 80× dilution of standards and samples prior to injection. Within day repeatabilitys (n=7) of migration times (RSD%<0.15) and peak areas (RSD%<5) as determined for a wine sample were found to be excellent. The method was applied to 20 South African wine samples, and the results are compared to data obtained by ion-exclusion liquid chromatography. Succinic acid was consistently overestimated using the latter technique, while for the other acids good agreement between the methods was noted.

Analysis of Organic Acids in Wine by Capillary Electrophoresis with Direct UV Detection

A capillary electrophoretic method using a phosphate-based carrier electrolyte and direct UV detection at pH 6.5 for the routine determination of five organic acids in wine samples is described. The present method shows advantages over other commonly applied method based on phthalic acid buffer with indirect UV detection for the quantification of organic acids. Factors that affect capillary electrophoretic separation such as concentration and pH of the background electrolyte, concentration of the electroosmotic flow modifier, and methanol addition were considered. Separation and determination of tartaric, malic, acetic, succinic and lactic acids were achieved in approximately 6 min. The method was quantitative, with recoveries in the 98–107% range, and linear over more than one order of magnitude. The precision is better than 0.94–1.06% for migration time and 0.40–0.96% for peak area. The method is sensible, with detection limits between 0.015 and 0.054 mg L −1. The usefulness of the method was successfully demonstrated by the analysis of the considered organic acids in 39 red wines from two different Spanish Certified Brands of Origin (CBO). Determinations were made by direct injection after the appropriate sample dilution and filtration. Distributions of organic acids in Ribeira Sacra wines show a predominance of lactic (3784–452 mg L −1) and tartaric acids (1987–866 mg L −1) followed by succinic (897–398 mg L −1), malic (2844–not detected mg L −1) and acetic (749–116 mg L −1) acids. An analogous distribution was observed in the Bierzo wines: lactic acid (4037–179 mg L −1), tartaric acid (1819–772 mg L −1), succinic acid (646–389 mg L −1), malic acid (1513–not detected mg L −1) and acetic acid (553–214 mg L −1).

High-performance liquid chromatography with real-time Fourier-transform infrared detection for the determination of carbohydrates, alcohols and organic acids in wines

The coupling of high-performance liquid chromatography (HPLC) with Fourier-transform infrared spectroscopy (FTIR) is presented as a new and versatile tool for the direct determination of the main components of wine, which are glucose, fructose, glycerol, ethanol, acetic, citric, lactic, malic, succinic and tartaric acid. An ion-exchange resin based column (counterion: H +) was employed as the stationary phase and 0.005 M sulfuric acid as the mobile phase. FTIR detection in the spectral region from 1600 to 900 cm −1 was performed in a 25-μm flow cell without elimination of the solvent. Characteristic FTIR spectra were obtained subsequent to the injection and separation of 2 mg/ml of each component. The average standard deviation of the investigated compounds was found to be 66 μg/ml in standard solutions containing 1–10 mg/ml of the analyte. The method was furthermore applied to real wine samples taken from a round robin test. An average deviation of 0.16 mg/ml from the external reference data was obtained.

A rapid automated method for wine analysis based upon sequential injection (SI)-FTIR spectrometry

A new process control methodology for the simultaneous determination of sugars, alcohols and organic acids in wine based on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to ethanol several lower level wine components (glucose, fructose, glycerol, citric-, tartaric-, malic-, lactic- and acetic acid) were determined. To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel, fully automated sequential injection (SI) system with Fourier transform infrared (FTIR) detection. The resulting spectra were evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the analysis of real wine samples containing 79–91 g L–1 ethanol, 5.9–8.1 g L–1 glycerol, 0.4–6.9 g L–1 glucose, 1.5–7.5 g L–1 fructose, 0.3–1.6 g L–1 citric acid, 1.0–1.7 g L–1 tartaric acid, 0.02–3.2 g L–1 malic acid, 0.4–2.8 g L–1 lactic acid and 0.15–0.60 g L–1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR). The short analysis time (less than 3 min) together with high reproducibility makes the newly developed method applicable to process control and screening purposes (average of the standard deviations calculated from four repetitive measurements of six different real samples: ethanol: 0.55 g L–1, glycerol: 0.037 g L–1, glucose: 0.056 g L–1, fructose: 0.036 g L–1, citric acid: 0.020 g L–1, tartaric acid: 0.010 g L–1, malic acid: 0.052 g L–1, lactic acid: 0.012 g L–1 and acetic acid: 0.026 g L–1).

Artifactual Signal Splitting in the Capillary Electrophoresis Analysis of Organic Acids in Wine

An artifactual signal splitting was observed for acetic acid during the capillary zone electrophoresis of wine acids. Further study revealed that other comparably weak acids, propionic and butyric, show a similar split. Stronger carboxylic acids, formic, tartaric, malic, citric, and lactic acids showed no artifactual signal splits under the analysis conditions. Succinic acid showed intermediate behavior. The signal splitting could be eliminated by reducing the sample size and/or by employing the background electrolyte as the diluant.

Comparison of Three Chromatographic Systems for Determination of Organic Acids in Wine

Three chromatographic systems: ion exchange chromatography, ion exclusion chromatography and reversed phase chromatography, have been used for the simultaneous determination of organic acids in wine. The common organic acids were separated using all three chromatographic systems. When an ion exchange column (TSKgel 1C Anion-PW) was used, organic acids and inorganic anions (CI- and SO42-) in wine were determined simultaneously without interference. The sharp peaks were obtained when an ion exclusion column (TSKgel OApak-A) was employed. A rapid separation of organic acids has been achieved, within about 7 min, when a reversed phase column (Zorbax ODS) was used. In ion exclusion and reversed phase systems combined with UV detection, however, other organic compounds which have ultraviolet absorption at 210 nm interfered with the determination of organic acids when practical wine samples were analyzed. IC is an obvious alternative for determination of organic acids in wine.

Improved high-performance liquid chromatographic assay for determining organic acids in wines

Lactic, acetic, tartaric, malic, succinic and citric acids in wine samples were determined as phenacyl esters. The sample was buffered at pH 6.8, mixed with a solution of phenacyl bromide and a crown ether in acetone, and heated at 100°C for 40 min. An aliquot of the reaction mixture was subjected to reversed-phase high-performance liquid chromatography. Recoveries of the six acids were higher than 95%. The specificity of this assay was good as assessed by quantifying wine acids with other chromatographic techniques. The within-run coefficient of variation ranged from 1.7% for acetic acid to 3.1% for citric acid. When compared with a similar, recently reported assay, our assay gave more reliable results, especially for citric acid.

Esterification rates of main organic acids in wines.

The esterification rates (ratio of the concentration of an acid in the neutral ethyl ester form to total concentration of the acid) of main organic acids in wines were determined to study the extent of ethyl ester formation of organic acids. The esterification rates ranged from zero to 24.6%. The averaged values of table wines were from 6 to 16% for acetic and lactic acid, from 0.3 to 3.6% for succinic and malic acid, and from zero to 0.1% for tartaric acid. Sherries had higher esterification rates, about 1.6 to 6 times larger, than table wines. It was found that storage time and temperature influence the formation of ethyl esters, and it was suggested that the aging period required for the ester equilibrium is about one year for acetic and lactic acid, and more than two years for succinic, malic and tartaric acid. The possibility and the procedure to control wine quality during the aging process were discussed.

Review of Applications of Enzymatic Methods to the Determination of some Organic Acids in Wines

The essential characteristics of photometric enzymatic analyses are discussed along with application of these techniques to the determination of pyruvic acid, 2-ketoglutaric acid, malic acid, and L(+) lactic acid in wines. These determinations have shown for the first time the presence in wines of keto acids at levels of some tens (and even in some cases hundreds) of milligrams per liter. These simple specific and rapid enzymatic techniques permit the study of numerous intermediate metabolites which exist in small quantities in a natural material, the precise determination of which is very difficult in complex media such as wines Thus, a new path is opened in the progress of analytical enology and understanding of fermentation.

Applications of Chromatographic Methods to Organic Acids in Wine

Applications of Chromatographic Methods to Organic Acids in Wine