Soluble tannins in plum fruit (Prunus domestica L.)

Intensive breeding of European plum (Prunus domestica L.) for resistance against various diseases, especially sharka virus, has resulted also in cultivars with an astringent taste. Astringency is a known consequence of the presence of soluble tannins. The aim of the present study was to determine the content of total soluble tannins in flesh and peel of fruit of three plum cultivars ('Poznaplava, 'Plumtastic, 'jojo'), and three maturity classes. Total insoluble phenolic content was also determined. These data show that total soluble tannins represent in average 93.3% and 90.2% of the total soluble phenolic content in plum flesh and peel, respectively. The content of total soluble tannins depended on cultivar, fruit tissue, and maturity. 'Pozna plava' showed the highest content of total soluble tannins, and 'jojo' the lowest. Ripening resulted in lower total soluble tannins. The content of all analyzed phytochemicals in flesh was lower than that of peel. The fruit of the investigated cultivars contained up to 12-fold (flesh) and 22-fold (peel) more total insoluble than total soluble phenolic content.