Abstract
Polyphenols, antioxidant potential and color of three types of fortified Madeira wines were evaluated during the accelerated ageing, named as estufagem. The traditional estufagem process was set to 45 °C for 3 months. Overheating conditions, 1 month at 70 °C, were also examined. Total polyphenols (TP), total monomeric anthocyanins (TMA) and total flavonoids (TF) were assessed by spectrophotometric methods, while individual polyphenols and furans were simultaneously determined by HPLC-DAD. Antioxidant potential (AP) was estimated by ABTS, DPPH and FRAP assays, while color was evaluated by Glories and CIELab. Traditional estufagem decreased the TP and AP up to 20% and 26%, respectively, with final values similar to other wines. TMA of the Madeira wines from red grapes decreased during estufagem. Six hydroxybenzoic acids, three hydroxycinnamic acids, one stilbene, three flavonols and three flavan-3-ols were found in these wines. The prominent phenolics were hydroxycinnamates and hydroxybenzoates, even after estufagem. Most polyphenols decreased, with the exception of caffeic, ferulic, p-coumaric, gallic and syringic acids. Finally, both chromatic systems revealed that all wines tended to similar chromatic characteristics after estufagem. The study suggests that estufagem can be applied without high impact on polyphenols and antioxidant potential of these fortified wines.
Highlights
Together with aroma and taste, color is an essential feature in the sensory evaluation criteria of wine quality, influencing wine consumer selection
The experiments were focused on the evolution of the polyphenolic composition, antioxidant potential, and color of Madeira wines submitted to the traditional accelerated ageing, with the purpose of establishing the influence of temperature on this class of compounds
The results show that young wines produced from Tinta Negra Mole (TNM) grapes present similar levels of Total polyphenols (TP) when compared with the white variety Malvasia
Summary
Together with aroma and taste, color is an essential feature in the sensory evaluation criteria of wine quality, influencing wine consumer selection. Flavonoids are the major polyphenols in red wines, constituting more than 85% of the phenolic content and usually found in concentrations ranging from 1,000 to 1,800 mg/L, but less than 20% of these levels in white wines [1,4]. White wines possess less polyphenols than red wines, with hydroxycinnamates as the major ones These compounds, namely the esters of tartaric acid (caftaric and coutaric acids) together with some flavanols, like (+)-catechin and (−)-epicatechin, are considered the major oxidation substrates and browning precursors in white wines, to form yellow-brown products due to the polymerization of o-quinones [9,10]. The reactivity of polyphenols increases the complexity due to the variety of the resulting compounds and has an important effect on the sensorial properties of wines, especially on color due to wine browning, and in taste and colloidal stability during storage and ageing [13]
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