Effects of PH and sucrose concentration on butterfly pea (Clitoria ternatea) flower extract / Siti Hajar Mohd Noor

There are many factors influencing the stability of natural colourant anthocyanin in which sucrose concentration and pH is among the most significant factor. This study aims to determine the effects of pH, sucrose concentration and heat treatment on the total anthocyanin content, DPPH scavenging activity, ferric reducing antioxidant power, total phenolic content, and colour of Clitoria ternatea aqueous extract. The fresh Clitoria ternatea extract was found to have total anthocyanin content of 8.68±0.10 mg/L, DPPH scavenging effects 49.9±0.26%, ferric reducing antioxidant power 429.5±0.97 mg/100 g, total phenolic content 220.8±1.89 mg GAE/100 g, total colour difference 8.04±0.46 and the initial pH of 5.26±0.42. The extracts were then adjusted and evaluated at pH 2, 3 and 4; sucrose concentration of 10%, 20% and 30%; also after pasteurisation at 90 ºC for 60 minutes. The result shows that the highest value of total anthocyanin content (6.77±0.01 mg/L) was obtained at pH 3 with 30% sucrose concentration. The highest value of DPPH scavenging effects (63.52±0.57%) was obtained at pH 4 with 30% sucrose concentration. The highest value of ferric reducing antioxidant power (403.3±0.73 mg/100 g) was obtained at pH 4 with 10% sucrose concentration. The highest value of total phenolic content (160.9±0.95 mg GAE/100 g) was obtained at pH 3 with 10% sucrose concentration. The colour of the extract was found to shift from light red at pH 2 to light purple at pH 3 and light dark blue at pH 4; and the colour observed was intensified by the increase in sucrose concentration. In general, heat treatment caused reduction in total anthocyanin, antioxidant properties, total phenolic content and colour of the extract. Total anthocyanin content was found to decrease by 35.66% to 90.02%with the increase in pH and 35.66% to 90.23% with the decrease in sucrose concentration after heat treatment. DPPH scavenging effects was found to reduce 26.19% to 46.81% with the decrease in pH and 26.19% to 46.81% with the decrease in sucrose concentration. Ferric reducing antioxidant power was decrease by 10.50% to 28.38% with the increase in pH and 10.50% to 28.38% with the decrease in sucrose concentration. Total phenolic content was found to reduce by 6.47% to 31.70% with the increase in pH and 17.34% to 27.10% with the increase in sucrose concentration. The total colour difference was also found to decrease between 0.23% to 11.55% with the decrease in pH and 0.23% to 10.86% with the increase in sucrose concentration after heat treatment. Overall, the results obtained in this study can be use by the food and beverages industry in manipulating the natural colourant obtained from Clitoria ternatea to suits to their products properties.