Study On Extraction And Stability Of Red Pigment In TaiWan's XiangLong Hylocereus Undutus Fruit

Study on extraction and stability of red pigment in the pulp and peel of Taiwan's XiangLong Hylocereus undatus is applied in this paper. The result showed that different solvent effect the extraction obviously. The maximum absorption wavelength of water solution of the pigment in the pulp and peel were 538nm and 536nm respectively. The pigment could be melt by distil, pure water, waterworks, alcohol, acetone, iso-propylalcohol, acetic acid, citric acid, tartaric acid and 0.2 N HC1. The pigment was polarity or mini-polarity, next was distil and acetone. The best solvent was alcohol which concentration was 20%. Acetic acid, citric acid and tartaric acid, which are applied widely in the food industry , could deepen the pigment's color without changing its stability obviously. Acid condition was helpful to extract the pigment and stabilize the pigment, while alkali condition decreased its stability. According to the pulp and peel, the optimum pH were 6.5 and 5.0. The ratio of material to solvent had effect on the extraction . According to the pulp and the peel, the optimum ratio were 8.0:1 and 6.4:1. Mono-factor experiments and orthogonal experiments indicated that that solvent pH and ratio of material to solvent had obvious effect on the extraction, while the extraction was affected less by extracting temperature and time .As to the pulp, the optimum pH was 6.5, ratio of material to solvent was 8.0:1, extracting temperature was 40℃ extracting time was 1.5h. As to the peel, the optimum pH was5.0, ratio of material to solvent was 6.4:1, extracting temperature was 40 ℃ extracting time was 1h. The pigment was stable below 60 ℃ and turn to be yellow above 60 ℃. The pigment deepened its color and strengthened its stability in acid while it converted from bright red to yellow, maximum absorption wavelength changed from 536nm or 538nm to shortwave in alkali. Organic acids and carbohydrates could also deepen the pigment's color but could not effect its stability. Scatter light and darkness had no effect on the stability of the pigment, but sunrays and ultraviolet light could turn it to be yellow and decrease its stability. Oxidants and reducers could make the pigment discolor or fade. Some mental ions such as Mn2+, Na+ and K+ made the pigment deepen its color and raise its stability, but others such Zn2+ and Fe2+ made it fade and decreased its stability.