Optimising anthocyanin extraction from strawberry fruits using response surface methodology and application in yoghurt as natural colorants and antioxidants.

The aim of the present study was to optimise the extraction conditions of anthocyanins from strawberry fruits and incorporate them in yoghurt to achieve a natural coloration as well as enrich the product with antioxidants. The response surface methodology (RSM) based on Box-Behnken design was studied to assess the influence of the three factors being agitation speed (400-800 rpm), sample to solvent ratio (0.5-2 g/40 mL), and extraction time (1-15 min) on total anthocyanin content and antioxidant activity of strawberries. According to the results, the linear, quadratic and interaction effects of the studied factors on total anthocyanin content and antioxidant activity were determined by the response surface methodology, and the optimal conditions for anthocyanin extraction were 586 rpm for agitation speed, 1.26 g/40 mL for sample to solvent ratio, and 9.36 min for extraction time. Under these extraction conditions, the total anthocyanin content and antioxidant activity recorded by the two validated models were 38.04 mg C3GE/100 g FW and 21.38 mg AAE/100 g FW, respectively. The enriched natural yoghurt contains anthocyanins with a content of 36.50 µg C3GE/100 g and an antioxidant activity of 21.22 µg AAE/100 g. The anthocyanin enriched yoghurt developed in this study may be considered as a functional food with an interesting source of natural antioxidants, and these anthocyanins can substitute synthetic (industrial) colorants.