Lutein in Fruit Peel of Trichosanthes kirilowii Maxim. by Supercritical CO_2 Extraction and Its Stability

Supercritical carbon dioxide(SC-CO2) fluid extraction of lutein in fruit peel of Trichosanthes kirilowii Maxim.and the physical and chemical properties of lutein were investigated.The response surface methodology(RSM) was employed to optimize the process variables of three major factors.Experimental data were analyzed by solving the regression equation with the Design Expert Software.Fixed the particle size(0.25～0.42) mm and time 150 min,φ(ethanol)=95% as the entrainer.The optimum process parameters were obtained as:pressure,26.6 MPa;temperature,52.8 ℃;CO2 flow rate,15.7 L/h,at which the yields were 4.76 g/100 g and lutein mass fraction was 14.99%.The maximum absorption spectrum of the lutein was 445 nm.Light has a great influence on the stability of lutein.The absorbance of lutein decreaced 86.57 % under the sunlight 7 days.The lutein were relatively stable against heat but lutein degradation could be accelerated with the decreased preservation rate under long time and high temperature,90 ℃ heating for 3 h,the absorbance of lutein decreaced 17.48%.The lutein could degrade significantly under acid conditions(pH=1～4),but more stable in the neutral and alkaline conditions.The lutein were unstable with decreased preservation rate with Fe3+,Fe2+,Cu2+,Al3+,Mg2+ solution to place 4 d,lutein absorbance values decreased 29.23%,20.70%,30.80%,23.53%,30.93%.a small amount of flocculent precipitate appears in Mg2+ solution and while stable with Zn2+,Ca2+,K+,Na+.H2O2,ascorbic acid and citric acid has minor damage,sodium benzoate and low concentration ρ(Na2SO3)=0.2～0.4 g/L can enrich its color.In addition,sucrose has no effect on the lutein.