Incorporation of strawberries preparation in yoghurt: impact on phytochemicals and milk proteins.

An immediate decrease in the total antioxidant activity (23%) and total phenolic content (14%) was observed after addition of strawberry preparations to yoghurt. The total anthocyanin content did not change immediately, but decreased 24% throughout the yoghurt shelf-life. The individual compounds, (+)-catechin (60%), (-)-epicatechin (60%), kaempferol (33%) and quercetin-3-rutinoside (29%) decreased after 24h in the yoghurt made with the strawberry preparation. During the remaining period of storage these compounds increased by 47%, 6%, 4% and 18%, respectively. Pelargonidin-3-glucoside decreased 49% after 28 d. Immediately after the addition of the strawberry preparation to yoghurt, β-lactoglobulin decreased to values lower than the limit of detection and α-lactalbumin by approximately 34%, and was reduced further slowly throughout yoghurt self-life. An immediate interaction between the carrageenan present in the strawberry preparation and β-LG was observed. The variations of both polyphenols and protein in the presence of carrageenan and the potential interactions were discussed.