Abstract:

A solvent extraction technique was developed to extract the pigment from the wild cactus fruit in Hainan and optimized using the L₉ (3 ⁴) orthogonal test. The stability of the pigment to pH, temperature, light, metal ions and so on was also investigated. The optimal extraction conditions using distilled water were 10 min at pH 7.5 and 30 ℃ with a solid/liquid ratio 1∶20 (g/mL). Under the conditions, the yield of pigment was up to 7.75%. The pigment had good stability under pH 4~10, temperature less than 30 ℃, darkness conditions. The metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺ had no obvious effect on the stability of the pigment. However, metal ions Cu²⁺, Fe²⁺, Fe³⁺, Al³⁺ could worsen its stability, especially Cu²⁺ and Fe³⁺. Oxidizing agent, reducing agent Na₂SO₃ and Vc reduced the stability of the pigment.

Key words: cactus fruit pigment, solvent extraction, process optimization, orthogonal design, stability