The Study Of Physicochemical Property Of Anthocyanidin In Purple Pakchoi

Pakcho(iBrassica campestris L. ssp. chinensis Makino)blongs to colewort of cruciferae, which is one of the most popular cultivated vegetable in China. Purple pakchoi (ZiLuoLan) with purple leaf, rich in anthocyanidin, is a potential source of natural pigments.The distribution, component, extraction technology and physicochemical property of anthocyanidin in purple pakchoi leaves were studied. The results are as follows:1. Based on the hand-sliced technique, it was determined that the anthocyanidin of purple pakchoi mainly exist in the upper epidermis of leaf.2. The elemental component of anthocyanidin in purple pakchoi leaves is cyanidin-malonyl-glucoside through HPLC-ESI-MS/MS analysis.3. The freeze-drying powders(grain size≤0.46 mm) of leaf were used as experimental material. The extrcting method of anthocyanidin was set up through single factor parallel experiment: the best extracting solvent is 35%(volume percentage) acetic acid, the better extracting method is lixiviating way, solid(g)-liquid(mL)ratio 1:10, extracting temperature 25℃, extracting time 1 min and extracting twice, the accumulative extraction rate reached to 92.61%.4. Based on the spectral scanning of anthocyanidin solution treated with light, temperature, pH values, oxidization-reductant, metal ions and food additives, the physicochemical property of anthocyanidin in purple pakchoi were studied.(1) Spectral characteristics: the anthocyanin in purple pakchoi had 2 absorption peaks at 529 and 328nm respectively.(2) Solubility: the anthocyanin in purple pakchoi is easier soluble in water, then methanol, ethanol and acetic acid, but insoluble in acetone, toluene and acetidin. The colour and spectral characteristics of the anthocyanin were different in different solvents.(3) Light stability: the scattered light and fluorescent lamplight less influenced the stability of anthocyanidin, but the sunlight and ultraviolet strongly influenced it. The remainder ratio of anthocyanin dropped to 84.28% in sunlight for 8 h and 90.65% in ultraviolet for 8 h.(4) Thermal stability: high temperature influenced severely the stability of anthocyanidin. The remainder ratio dropped to 72.75% in boiling-water bathing for 2 h. (5) pH value Stability: the colour and spectral characteristics of the anthocyanin are different at different pH values. The treatment with pH 3, 5, 7, 9 respective had less effect on the stability of anthocyanidin, but pH 11 and pH 13 both had more effect on it. The remainder ratio of anthocyanin dropped to 29.80% at pH 11 for 2 h and 26.12%(without regard to the change of spectral characteristics) at pH 13 for 2 h, further more, the pH 13 treatment induced a blue shift of wavelength about 13 nm.(6) Oxidization-reductant stability: oxidant H₂O₂ influenced severely the stability of anthocyanidin. The remainder ratio of anthocyanin dropped to 34.56% in 0.2%(volume percentage) H₂O₂ for 2 h and 0% in 0.6% H₂O₂ for 2 h. A red shift of wavelength about 57 nm happened in reductant Na₂SO₃ for 2 h.(7) Metal ions stability: K⁺, Ca²⁺, Al³⁺, Na⁺, Mg²⁺ and Ba²⁺ had no influence on the stability of anthocyanidin; Cu²⁺ changed the colour of anthocyanin from deep red to purple; Fe³⁺ influenced severely, it not only changed the colour of anthocyanin from deep red to yellow, but also led to the disappearance of the characteristic absorption peak of anthocyanidin.(8) Food additives stability: sucrose, glucose, citric acid, NaCl, ascorbic acid all had little influence on the stability of anthocyanidin, but sodium benzoate had little hyperchromicity on it.