Identification of the anthocyanin profile from butterfly pea (Clitoria ternatea L.) flowers under varying extraction conditions: Evaluating its potential as a natural blue food colorant and its application as a colorimetric indicator

Abstract

This study aims to extract anthocyanins from BPF (Butterfly Pea Flower) to determine an effective solvent combination resulting in higher total anthocyanin content. Various solvent combinations were utilized to discern crucial characteristics of the obtained BPFE (Butterfly Pea Flower Extract). The BPFE from the optimal treatment was utilized as a pigment in colorimetric indicators, which were then evaluated for their initial response to seafood spoilage stored at room temperature for 24 h. The color change response of the colorimetric indicators employing BPFE pigment was compared with the pH and TVBN (Total Volatile base Nitrogen) values of the seafood initially and after 24 h. The highest total anthocyanin content was achieved with the combination of 96 % ethanol/1.5 N HCl (85:15, v/v) at 551.06 mg/L, followed by the combination of 96 % ethanol/distilled water (70:30, v/v) with pH adjustment to 1 using 1.5 N HCl at 484.27 mg/L. Subsequent combinations, in decreasing order, were 96 % ethanol/1.5 N HCl (99:1, v/v), 96 % ethanol/distilled water (70:30, v/v), and lastly, 96 % ethanol/distilled water (30:70, v/v), with total anthocyanin content of 275.53 mg/L, 200.39 mg/L, and 125.24 mg/L, respectively. BPFE applied in colorimetric indicators demonstrated responsiveness to seafood spoilage through color changes, with tested spoilage indicators being pH and TVBN. The initial (first hour) pH and TVBN values for each tested seafood were 5.5 and 9.42 mg/100 g (Scylla serrata), 6.4 and 4.23 mg/100 g (Litopenaeus vannamei), 5.4 and 11.29 mg/100 g (Uroteuthis sibogae), and 6.5 and 10.26 mg/100 g (Restrelliger kanagurta). Meanwhile, the pH and TVBN values after 24-h storage at room temperature became 7.9 and 57.01 mg/100 g, 7.4 and 76.65 mg/100 g, 7.5 and 216.44 mg/100 g, and 7.8 and 51.86 mg/100 g, respectively. The conclusion drawn is that the extraction of BPFE is more efficient when utilizing acidified ethanol solvent, and the resulting BPFE holds promise as a reliable pH indicator.