Acid In Wine Samples Research Articles

Gas chromatographic amino acid profiling of wine samples for pattern recognition

A rapid gas chromatographic profiling and screening method is described for the determination of free amino acids in wine samples. The amino acids in alkaline aqueous wines were allowed to react with isobutyl chloroformate. The resulting N(O,S)-isobutyloxycarbonyl amino acids were extracted by solid-phase extraction using Chlomosorb P as the adsorbent and diethyl ether as the eluent after acidification, and then converted into stable tert.-butyldimethylsilyl derivatives with subsequent analysis by dual-capillary column gas chromatography and gas chromatography-mass spectrometry. Seventeen free amino acids were identified from the four wine brands studied. When the GC profiles were simplified to the corresponding amino acid retention index spectra in bar graphical form, they presented characteristic patterns for each wine brand. Stepwise discriminant analysis performed on the amino acid profiles provided star symbols characteristic of the wine brands.

Determination of free amino acids by precolumn derivatization with phenylisothiocyanate. Application to wine samples

A method to determine free amino acids by pre-column derivatization with phenylisothiocyanate is discussed. The method has been applied to determine free amino acids in wine samples, and the results have been compared with those obtained by means of an automatic orthophthal-aldehyde-9-fluorenylmethyloroformate (OPA-FMOC) method.

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.