ABSTRACT
UNLABELLED: Stilbene-enriched wine is considered to be an interesting new food product with added value due to its potential health-promoting properties. Stilbene concentration in grape is highly variable and rather scarce. However, it can be increased by stress treatments. For this reason, numerous pre- and postharvest grape treatments, and some combinations of them, have been tested to maximize stilbene content in grapes. In the present manuscript, Syrah grapes were treated with (i) methyl jasmonate (MEJA), (ii) ultraviolet light (UVC), and (iii) methyl jasmonate and ultraviolet light (MEJA-UVC) and compared with untreated grapes. Afterward, winemaking was developed. Wine achieved by combination of both treatments (MEJA-UVC) contained significantly higher stilbene concentration (trans-resveratrol and piceatannol) than its respective control (2.5-fold). Wine quality was improved in color-related parameters (color intensity, L*, a*, b*, ΔE*, anthocyanins, and tannin). Moreover, MEJA-UVC wines obtained the highest score in sensorial analysis. To the best of our knowledge, this is the first time that pre- and postharvest treatments are combined to increase stilbenes in wine. PRACTICAL APPLICATION: The effect of treatment combination (methyl jasmonate and UVC light) on grape and wine was evaluated. Our results highlight the positive effect of the treatments in stilbene content, color parameters, and sensorial analysis. Moreover, added-value by-products were achieved.
Subject(s)
Acetates/pharmacology , Cyclopentanes/pharmacology , Fruit/metabolism , Oxylipins/pharmacology , Plant Growth Regulators/pharmacology , Stilbenes/metabolism , Ultraviolet Rays , Vitis/metabolism , Wine/analysis , Anthocyanins/metabolism , Color , Fruit/drug effects , Fruit/radiation effects , Humans , Odorants , Resveratrol , Tannins/metabolism , Taste , Vitis/drug effectsABSTRACT
Stilbenes are a family of bioactive compounds found in plants. However, only a few stilbenes are present in the human diet. Grape and wine are the main dietary source of stilbenes, resveratrol and piceid being the most common ones. Ultraviolet C light (UVC) postharvest treatment was used to obtain significantly increased stilbene concentration in grapes. A new, previously undescribed-in-grapes stilbene was found after UVC treatment. The process followed to isolate and identify this unknown stilbene is described in the present work. This isolation involved several fractionation steps including counter current chromatography and semi-preparative HPLC due to its low concentration and the presence of structurally related compounds. The structure of the compound was unequivocally identified by NMR spectroscopy analyses including (1)H-NMR; COSY; ROESY; HSQC and HMBC. The compound was identified as isorhapontigenin (ISOR), a stilbene found in traditional Asian medicinal plants. To the best of our knowledge this is the first report of its occurrence in grapes.
