Abstract: Total phenolic content (TPC), total flavonoid content (TFC) and total proanthocyanin content (TAC) were determined in the whole berries, juice and pomace of strawberry, blackberry and blueberry. Meanwhile, their total antioxidant capacity (trolox equivalent antioxdant capacity, TEAC) was analyzed by an improved ABTS+ radical scavenging assay. The results showed that blueberry contained the highest levels of TPC, TFC and TAC, which were 9.44 mg gallic acid/100g dry , 36.08 mg rutin/g and 24.38 catechin mg/g, respectively. Blueberry also possessed the strongest total antioxidant capacity with a TEAC (trolox equivalent antioxidant capacity) value at 14.98 mmol Trolox /100 g. In contrast, strawberry contained the lowest levels of TPC, TFC and TAC as well as the lowest total antioxidant capacity. For all the three varieties of berries, the pomace contained the most TPC, TFC and TAC and revealed the highest level of TEAC, followed by the whole berry and juice. In addition, a significant linear correlation between TPC and TEAC was observed with a correlation coefficient (r)of 0.9704, suggesting that phenolic compounds in berries were mostly responsible for their antioxidant activity.

Key words: strawberry, blackberry, blueberry, phenolics, flavonoids, proanthocyanins, antioxidant capacity