Abstract: Changes in the contents of total phenolics, total flavonoids and anthocyanins and antioxidant activity of blueberry incorporated in yoghurt were determined during 21 d of storage at 4 ℃ and digestion in vitro. The antioxidant activity was evaluated by total antioxidant capacity, DPPH radical scavenging and ABTS radical scavenging assays. The results showed that the contents of total phenolic compounds, total flavonoids and anthocyanins, total antioxidant capacity, and DPPH and ABTS radical scavenging activity were 46.14, 41.63, 9.01, 44.51, 59.49 and 61.39 mg/100 g at the beginning of storage, which decreased by 10.20%, 9.86%, 15.54%, 6.52%, 7.23% and 6.03% at the end of storage, respectively. These decreases were smaller than those (1.93%, 3.46%, 0.03%, 3.58%, 4.17% and 4.91%, respectively) observed for blueberry alone indicating that yoghurt decreased the stability of phenolic compounds and had a negative effect on antioxidant activity. A decrease in all these parameters was observed comparing blueberry added to yoghurt with blueberry alone, and after in vitro digestion, the comparison showed a decrease in total flavonoids content and DPPH radical scavenging activity but an increase in the contents of total phenolics and anthocyanins, total antioxidant capacity and ABTS radical scavenging activity, which indicated that simulated gastrointestinal digestion could promote the release of antioxidant substances from blueberry incorporated in yoghurt.

Key words: blueberry incorporated in yoghurt, stability of polyphenols, antioxidant activity, storage time, in vitro digestion