Colour and antioxidant capacity stability in grape, strawberry and plum peel model juices at different pHs and temperatures

The aim of the study was to evaluate the anthocyanin sources potential as natural food colouring. Model juices (MJs) of grape, strawberry and plum peel were stored during 8 weeks in darkness at 6 and 23 °C. The colour stability was evaluated at pH 2.4, 3.1, 4.0, 5.0, 6.0, 7.0 and 8.1, and the antioxidant capacity at pH 4.0. The plum peel MJ showed the best and more stable colour parameters. The grape MJs presented a high stability although the chroma values were very low. The storage of strawberry MJ demonstrated a low stability at 23 °C. The vitamin C equivalent antioxidant capacity in grape, strawberry and plum peel MJs was 7, 40 and 50 mg/L, respectively. The strawberry MJ stability was very low. Total phenolics and anthocyanins ranged between 18–101 and 2–62 mg/L of MJ, respectively. The determination coefficient was R2 = 0.745 between the antioxidant capacity and total phenolics.