Improving the Phloroglucinolysis Protocol and Characterization of Sagrantino Wines Proanthocyanidins

Abstract

Proanthocyanidins are key metabolites that explain wine sensorial character (bitterness and astringency) and red wine color changes during aging. Therefore, a fast and accurate method to evaluate the degree of polymerization and the structural composition of the polymeric proanthocyanidins is a crucial analytical tool. Phloroglucinolysis is the most used method for this analysis but, unfortunately, the phloroglucinol adducts of the monomeric flavan-3-ols are not commercially available, making the results less accurate. The aim of this work was the isolation by semi-preparative high performance liquid chromatography (HPLC) of these non-commercial compounds and their use for the development of an accurate UHPLC-MS/MS protocol. The purity of each adduct was established via quantitative 1H-nuclear magnetic resonance (NMR) measurements with 3-trimethylsilyl-propionic-d4 acid sodium salt as the calibration standard. The developed method was applied to evaluate the proanthocyanidins profile of Sagrantino di Montefalco wines in comparison to other well-known tannic wines. Commercial, 6–8 years old Sagrantino wines were demonstrated to be very rich in epicatechin type B procyanidins, to have low galloylation %, and to have a high mean degree of polymerization of the proanthocyanidins with respect to the other analyzed wines.

Role of Grape-Extractable Polyphenols in the Generation of Strecker Aldehydes and in the Instability of Polyfunctional Mercaptans during Model Wine Oxidation

“…The phloroglucinolated derivatives EC 4-phloroglucinol, EC-gallate 4-phloroglucinol, and EGC 4-phloroglucinol were prepared according to Arapitsas et al, 2021. 20 …”

“…Highest purity (>98%) grade­(+)-catechin, (−)-EC, (−)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-EC gallate (ECG), procyanidin B1, and procyanidin B2 were obtained from TransMIT PlantMetaChem (Gießen, Germany). The phloroglucinolated derivatives EC 4-phloroglucinol, EC-gallate 4-phloroglucinol, and EGC 4-phloroglucinol were prepared according to Arapitsas et al, 2021 …”

“…The phloroglucinolated derivatives EC 4-phloroglucinol, EC-gallate 4-phloroglucinol, and EGC 4-phloroglucinol were prepared according to Arapitsas et al, 2021. 20 Polyphenolic and Aroma Fractions. The 15 polyphenolic aromatic fractions (PAFs) were extracted from 15 lots of grapes from three different Spanish wine-making regions (La Rioja, Ribera del Duero, and Somontano) and three different grape cultivars (7 from Tempranillo, 6 from Garnacha and 2 from Moristel), as described in Alegre et al 21 Briefly, 10 kg of grapes was collected at technological maturity, kept at 5 °C during the transport to the experimental cellar, destemmed and crushed in the presence of 50 mg/Kg of potassium metabisulfite and ethanol (adjusted to 15% v/v), and left in the dark at 13 °C for 7 days in closed recipients with no headspace after pressing to obtain the liquid mistella (ethanolic must), which after sterile filtration was stored at 5 °C in 750 mL wine bottles closed with a natural cork and no headspace.…”

“…Anthocyanins were analyzed by ultra-HPLC−MS/MS, as described by Arapitsas et al 23 Flavanols, flavonols, and hydroxycinnamic acids were analyzed, as described by Vrhovsek et al, 24 by UHPLC−MS/MS. The mean degree of polymerization (mDP) was determined by UPLC−MS/MS analysis of the phloroglucinol reaction, as described by Arapitsas et al 20 520 nm) at four different temperatures (30,35,40, and 45 °C), as the specific enthalpy of interaction between tannins and a hydrophobic surface (polystyrene divinylbenzene HPLC column), as proposed by Yacco et al 25 The concentration of total and pigmented tannins were determined in the chromatogram made at 30 °C and they were reported in EC equivalents and area data, respectively. Chemical Characterization of Oxidized and Unoxidized (Controls) Wine Models.…”

Tannin Content in Vitis Species Red Wines Quantified Using Three Analytical Methods

“…Condensed tannins are oligomer and polymer of flavan-3-ols, which are extracted from grape skins and seeds during alcoholic fermentation and extended maceration in red wine making [ 7 ]. Condensed tannins are characterized by the type of constitutive subunits linked mainly through C4-C8 linkages, and the number of these subunits provides an indication of the mean degree of polymerization [ 8 , 9 ]. As previously described, the size of condensed tannins is positively related to their ability to interact with proteins and polysaccharides.…”