Sources and Health Effects of Dietary Ellagitannins - Chemistry and Biology of Ellagitannins - page 306

ellagic acid after acid hydrolysis, 360-910 mg/kg (Lee et al. , 2005). In
ripe grapes, more than 80% of the total ellagic acid compounds is
localized in the skin, and ripe grapes have higher levels than unripe
grapes (Lee and Talcott, 2004).
In muscadine grape juices prepared from different red and white
grape cultivars, total ellagic acid concentrations of 100-300 mg/L were
measured (Lee and Talcott, 2004). Concentrations of free ellagic acid
and ellagic acid glycosides were 4-23 mg/L and 10-30 mg/L,
respectively. Processing technologies (extraction and fermentation
techniques) and cultivar influence the concentrations of ellagic acid and
ellagitannins in juice and wine. Juices have higher levels compared to
wines, indicating loss of ellagitannins during wine production and
storage (Lee and Talcott, 2002).
During storage, muscadine juice and wine may produce a water-
insoluble precipitate of yellowish to red crystals. Sediments are usually
considered as quality defects and influence consumer acceptability of
muscadine grape products. Ellagic acid was identified as the
predominant component of the sediment (Boyle and Hsu, 1990). Due to
hydrolysis of ellagitannins during storage and poor solubility of free
ellagic acid, the content of free ellagic acid increases in the sediment
(Lee and Talcott, 2002). Only about 12% of the weight of the sediment is
ellagic acid, with the rest consisting of unidentified compounds and
traces of ellagitannins.
8.2.5 Oak-aged wine
Although the content of ellagitannins in common grapevine ( Vitis
vinifera ) is low, ellagitannins are common in wines aged in oak barrels.
Ellagitannins of oak heartwood, such as vescalagin and castalagin, are
potentially extracted into wine during aging and contribute to the sensory
properties of the wine (Puech et al. , 1999). The oak ellagitannins also
react with grape phenolics and ethanol producing flavano-ellagitannins
and other derivatives. In a Bordeaux red wine aged for 18 months in oak
barrels, the concentrations of oak ellagitannins were about 10 mg/L and
those of flavano-ellagitannins about 2 mg/L (Saucier et al ., 2006).