From grape to wine: Changes in phenolic composition and its influence on antioxidant activity

Area of Science:

• Enology and Viticulture
• Food Chemistry
• Plant Biochemistry

Background:

• Phenolic compounds are crucial for wine quality and possess antioxidant properties.
• Understanding their evolution during winemaking is key to optimizing wine production and utilizing by-products.
• Vitis vinifera L. cvs. Syrah, Merlot, and Cabernet Sauvignon are globally significant grape varieties.

Purpose of the Study:

• To investigate the changes in phenolic compounds and antioxidant capacity (AC) throughout the winemaking process.
• To determine the relationship between specific phenolic compounds and the overall AC of wines.
• To compare phenolic profiles and AC across Syrah, Merlot, and Cabernet Sauvignon varieties grown in Argentina.

Main Methods:

• High-performance liquid chromatography with photodiode array and tandem mass spectrometry (HPLC-PDA-MS/MS) for phenolic compound identification.
• Ferric reducing antioxidant power (FRAP), ABTS, and DPPH assays for measuring antioxidant capacity.
• Multiple regression analysis to correlate phenolic composition with AC.

Main Results:

• Phenolic composition and AC varied significantly during winemaking and differed between grape varieties.
• Anthocyanins were identified as the primary contributors to the antioxidant capacity.
• Quantitative variations in specific phenolic compounds explained differences in AC among the studied Vitis vinifera cultivars.
• Grape pomace retained substantial phenolic content and antioxidant bioactivity.

Conclusions:

• Anthocyanins play a critical role in the antioxidant capacity of wine.
• Grape variety and winemaking stage significantly impact phenolic profiles and AC.
• Grape pomace represents a valuable and economical source of natural antioxidants for potential industrial applications.