Interpretations of ultraviolet absorption in white wines

Abstract

Methods are described for the general analysis of total ultraviolet (u.v.) absorbing constituents of white wines. An elution profile, which is characteristic of the particular wine, is obtained by continuous monitoring of effluent from a dextran gel column at 280 nm. Surprisingly, about half of the total U.V. absorbance in the Riesling wine examined was found to be due to non-phenolic wine constituents, which are separately eluted in the gel column analysis. These are nucleotidic materials, to which little attention has previously been given in oenology.Data relating to the protein-tannin fraction, and to nucleotidic and phenolic constituents, are directly obtained by recording the wine elution profiles at 265, 280 and 320 nm. The interpretation of the elution curves and the significance and general utility of this new analytical method are discussed.

Technological approaches to the vinification of Dornfelder grape variety cultivated in Romania

“…The colour-related parameters and polyphenol content were determined by Glorie methodology [15,16], Somers and Evans [17] and OIV methods. Total polyphenol index was measured at 280 nm in absorbance units, corrected with a factor of 3.9 accounting for non-polyphenol substances absorbing at 280 nm [18]. All the spectrophotometric determinations were conventionally referred to the optical path of 10 mm and performed in quartz or glass cuvettes with a UV-VIS double beam spectrophotometer Specord 250 from Analytik Jena AG, running the software WinAspect version 2.2.7.…”

Phenolic Composition of Natural Wine Types

“…Approximate assessment of flavonoid extractives (A.max 280 nm) can be made from the wine spectrum after correction for absorbance of non-phenolics and of the hydroxycinnamates at 280 nm; E 280 of the total hydroxycinnamates is about 2/3 that of E320 (Somers and Ziemelis 1972). Thus the derivation:…”

“…Wavelength (nm) T. C. Somers and E. Verette Gel column analysis enabled introduction of a correction factor (4.0 in 10 mm pathlength) for UV contributions of total non-phenolics in wines and juices at 280 nm (Somers and Ziemelis 1972;Somers and Evans 1977). This was supported by later study of the effects of massive fining (10% w/v) with polyvinyl polypyrrolidone (PVPP) on UV spectra of many white wines and juices (e.g.…”

Interpretation of Ultraviolet Absorption in Wort and Beer. The Major Role of Nucleic Acid Derivatives

“…The content of monomeric phenolics, though very low in the samples examined, is also indicated by the elution profile beyond about Vo 160 ml in our analy tical system, as found with white wines. 10 The profiles are reproducible characteristics of the particular material, and the method is recommended for use in the preliminary evaluation of qualitative and quantitative differences in composition which relate to the above components.…”