Effects of Metal Ions on the Stabilization of Anthocyanin Pigments Powder from Butterfly Pea Flowers

¹ Department of Industrial Chemistry, Faculty of Applied Science, King Mongkut’s University of Technology North Bangkok, Wongsawang, Bang Sue, 10800 Bangkok, Thailand
² Integrated Chemistry Research Center for Sustainable Technology, King Mongkut’s University of Technology North Bangkok, Wongsawang, Bang Sue, 10800 Bangkok, Thailand

^* Corresponding author: voranuch.s@sci.kmutnb.ac.th
^† Corresponding author: sarinya.s@sci.kmutnb.ac.th

Abstract

Butterfly pea (Clitoria ternatea L.) flowers have been recognized as a natural source of anthocyanins, particularly delphinidin, which is used as a natural colorant but is highly susceptible to degradation influenced by environmental factors such as pH and temperature. In this study, the co-pigmentation of butterfly pea anthocyanins with metal ions (Al³⁺, Fe²⁺, Zn²⁺, Mg²⁺, and Ca²⁺) was evaluated under pH conditions of 4, 7, and 10, using a non-metal control for comparison. Total anthocyanin content (TAC), percentage of yield, and color measurement (L*, a*, b*, ΔE) were analyzed before and after accelerated heat and cooling cycle stability testing. The highest TAC (35.8 mg/L) and percentage of yield (98.95%) were obtained with Al³⁺ at pH 4. Minimal ΔE values (0.11–0.17) were observed in Al³⁺treated samples across all pH levels, indicating excellent color stability, whereas significant color degradation (ΔE 4.64–8.29) was observed in the control group. These results indicate that anthocyanin stability can be significantly enhanced by Al³⁺, followed by Fe²⁺ and Zn²⁺, suggesting the potential of metal-assisted co-pigmentation in improving the stability and functionality of natural colorants for applications in food, cosmetics, and related industries.