Anthocyanin copigmentation and color attributes of bog bilberry syrup wine during bottle aging: Effect of tannic acid and gallic acid extracted from Chinese gallnut

Tannic and gallic acids, extracted from Chinese gallnut, were applied as copigments to bog bilberry syrup wine with two different mass ratios of 1:2.5 and 1:6 of anthocyanin to copigment. The effect of copigmentation on anthocyanins and the changes in non-anthocyanin compounds and color characters during 6 months of aging were studied. Addition of copigment significantly helped to retain redness while reduced increase in the yellow shade and lightness. After 6 months of aging, the syrup wines with added copigments had 1.4-1.8 times higher total anthocyanin content compared to the control. The percentage of polymeric anthocyanins in copigment treated wines was lower than in control wine. Oppositely, the copigment treated wines possessed a higher percentage of copigmented anthocyanins than the control. The highest value of redness, the lowest percentage of polymeric anthocyanins and the highest percent of copigmented anthocyanins were presented in the wines treated with a high dosage of gallic acid. Practical applications Bottle aging shows a negative effect on the appearance of bog bilberry syrup wine. Copigmentation between anthocyanins and copigments is an alternative approach to prevent the loss of color during aging. However, the high expense of pure copigments limits the application of this protocol in wine industry. The cheaper copigments of tannic acid and gallic acid, extracted from Chinese gallnut, were used in the present study and presented positive effects on remaining red hub of bog bilberry fermented products through the enhancement of anthocyanin copigmentation. The current study provides new insights on exploiting somewhat poorly utilized bog bilberry byproduct in wine industry. The findings also verify the practicable of the economical copigments of Chinese gallnut extracted tannic and gallic acids in bog bilberry fermented products. On the other hand, observations made with bog bilberry in this study may be exploited with other berry materials, as well.