Characterisation of Extracts Obtained from Unripe Grapes and Evaluation of Their Potential Protective Effects against Oxidation of Wine Colour in Comparison with Different Oenological Products

• Main Authors: Giovanna Fia, Ginevra Bucalossi, Bruno Zanoni
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Foods
• Subjects: antioxidant extracts; unripe grapes; wine colour; anti-browning effect; phenols; SO₂
• Online Access: https://www.mdpi.com/2304-8158/10/7/1499

Unripe grapes (UGs) are a waste product of vine cultivation rich in natural antioxidants. These antioxidants could be used in winemaking as alternatives to SO₂. Three extracts were obtained by maceration from Viognier, Merlot and Sangiovese UGs. The composition and antioxidant activity of the UG extracts were studied in model solutions at different pH levels. The capacity of the UG extracts to protect wine colour was evaluated in accelerated oxidation tests and small-scale trials on both red and white wines during ageing in comparison with sulphur dioxide, ascorbic acid and commercial tannins. The Viognier and Merlot extracts were rich in phenolic acids while the Sangiovese extract was rich in flavonoids. The antioxidant activity of the extracts and commercial tannins was influenced by the pH. In the oxidation tests, the extracts and commercial products showed different wine colour protection capacities in function of the type of wine. During ageing, the white wine with the added Viognier UG extract showed the lowest level of colour oxidation. The colour of the red wine with the UG extract evolved similarly to wine with SO₂ and commercial tannins. The obtained results indicated that natural and healthy UG extracts could be an interesting substitute for SO₂ during wine ageing.