Thomas Giagou,* Kanwaljit Bajwa, Hui Chong, and Nick Dokoozlian
*E & J Gallo Winery, 600 Yosemite Blvd., Modesto, CA, 95354 
(thomas.giagou@ejgallo.com)

Anthocyanins are water-soluble compounds belonging to the flavonoid family, synthesized via secondary metabolic pathways in plants. In addition to their role in red wine color and color density, there is strong evidence that anthocyanins have important antimicrobial, anti-inflammatory, and antioxidant properties. Anthocyanin stability is influenced by many factors, including pH, temperature, ultraviolet light, oxygen, enzymes, and co-pigmentation. Sugar molecules can reduce degradation of unstable anthocyanin intermediates into phenol and aldehyde acid molecules. The presence of two sugar molecules in anthocyanin structures (di-glucosides) increases their stability more than having only one sugar molecule (mono-glucosides). Anthocyanin stability is further enhanced by increased methylation and decreases as more hydroxyl groups are added to the B-ring of anthocyanidins. Therefore, it is imperative to monitor the composition of anthocyanins to better understand color stability and its contribution to wine quality. The present analytical method, implemented on an Agilent high-performance liquid chromatography instrument with diode-array detection, provides an opportunity to quantitatively measure five mono-glucosides (delphinidin 3-O-glucoside, cyanidin 3-O-glucoside, petunidin 3-O-glucoside, peonidin 3-O-glucoside, and malvidin 3-O-glucoside) and five di-glucosides (delphinidin 3,5-di-O-glucoside; pelargonidin 3,5-di-O-glucoside; peonidin 3,5-di-O-glucoside; malvidin 3,5-di-O-glucoside; and cyanidin 3,5-di-O-glucoside) of anthocyanins in grape and wine. Analysis of seven Vitis vinifera varieties (Cabernet Sauvignon, Merlot, Petit Verdot, Petite Sirah, Teroldego, Pinot noir, and Zinfandel) established the dominance of mono-glucoside anthocyanins in all varieties. However, Napa Valley Cabernet Sauvignon contained elevated amounts of cyanidin 3,5-di-O-glucoside (up to 94.5 mg/L) and peonidin 3,5-di-O-glucoside (up to 78.9 mg/L). These results provide the potential to produce wine with improved color stability.

Funding Support: E & J Gallo Winery