A study of the proline isomerisation in typical Italian wines

Abstract

In this paper the presence of the D isomer of proline in wine was investigated. The analyses were carried out on samples of two different types of Italian red wines, ‘Merlot’ and ‘Cabernet’, at different stages of aging during the period 1987–1996. The quantitative determination was performed using an RP–HPLC apparatus equipped with a diode array detector. Marfey's reagent, (1‐fluoro‐2,4‐dinitrophenyl)‐5‐L‐alanine amide (FDAA), was used for the derivatisation, and the obtained diastereomers were separated on a Supelcosil LC‐18 analytical column (25 cm × 0.4 cm id), adopting a gradient procedure and making use of water/acetonitrile buffer as the mobile phase. L‐Norluecine was used as the internal standard for quantitative determination, and the detection of the derivatised components was made at a fixed wavelength of 340 nm. The data obtained show an interesting correlation between the age of the sample and the presence of the D‐proline isomer, due to a racemisation process that can be described as a first‐order kinetic reaction. The values of the kinetic constants obtained for the two wines are very similar but differ significantly from those observed for wines aged for more than 10 years. This is probably due to enzymatic degradation processes, which can occur in wine after longer periods of time. © 1999 Society of Chemical Industry

Use of Marfey's reagent and analogs for chiral amino acid analysis: Assessment and applications to natural products and biological systems

“…Using MR for derivatization, in Italian red wines small quantities of d-Pro (2-14 mg/L) besides the dominant lPro (ca. 1000 mg/L) could be determined [79]. That data is in rough agreement with those from European wines analyzed by direct enantioseparation using GC-MS and Chirasil-l-Val capillary columns [80].…”

Mass Spectrometric Detection and Formation of d-Amino Acids in Processed Plant Saps, Syrups, and Fruit Juice Concentrates

“…Consequently, the use of D-amino acids as chemical markers for food processing in terms of good manufacturing practice, nutritional value, maturation, food quality and authenticity, shelf life, food hygiene, and microbial contamination resulting in spoilage requires thorough knowledge on the occurrence and genesis of D-amino acids in raw materials and processed foodstuffs. This point was, and still is, the subject of intensive investigations (12)(13)(14)(15)(16)(17). We were puzzled by the fact that the abundance and diversity of D-amino acids in certain foods and beverages such as dried fruits, honey, or fortified wines, in comparison to table wines, could not be satisfactorily and unambiguously rationalized by applying established chemical or enzymatic racemization mechanisms or the action of bacteria (15,16,(18)(19)(20).…”

“…This point was, and still is, the subject of intensive investigations (12)(13)(14)(15)(16)(17). We were puzzled by the fact that the abundance and diversity of D-amino acids in certain foods and beverages such as dried fruits, honey, or fortified wines, in comparison to table wines, could not be satisfactorily and unambiguously rationalized by applying established chemical or enzymatic racemization mechanisms or the action of bacteria (15,16,(18)(19)(20). It was realized, however, that heating of saccharides together with L-amino acids led to the formation of D-amino acids (21).…”

Determination of Free Proline and Monosaccharides in Wine Samples by High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD)

“…Within all red wines investigated, the level of proline was found to range from 470 to 1190 mg/L, with higher concentration in the vintage of 1997. It is interesting to note that the content of proline in Merlot and Cabernet Italian red wines was well within such a range, 952 mg/L and 672 mg/L, respectively (6). Even though no significant differences in the sugar composition were obtained by analyzing wines of the same vintage and grape variety, distinctive sugar profiles (fingerprinting) were observed.…”

“…Nitrogen compounds, especially amino acids, are particularly important in enology with regard to their influence on the organoleptic profile and bouquet of wines (4). Free amino acids enhance taste and color of wine (5) and represent a group of substances for wine differentiation and classification (6). This was used to separate authentic Champagnes from sparkling wines, where the second fermentation to produce the overpressure of CO 2 is performed in the bottle, leading to an increase of amino acidic content (7).…”