Study On The Extraction And Purification Technology Of High-purity D-Limonene From Citrus

D-limonene is a member of cyclohexanoid monoterpenes,which is especially found in citrus,vegetables and spices.It has great development-perspectives for its anti-cancer,antibacterial and other physiological functions,is widely used as flavour and fragrance additive in food and perfume industry,and also used in pharmaceutical industry for its physiological function.The thesis is about the extraction and purification of d-limonene aming at acquiring d-limonene product with high-content limonene. Taking citrus essential oil and citrus peel residues as raw materials,the vacuum distillation extraction,water steam distillation,Supercritical Fluid Extraction-CO₂ and chemical purification were used;and also the content of d-limonene in different citrus varieties juices and peels,concentration juices and fresh orange juices were determined and analyzed,and the statistic datas of d-limonene content in Citrus fruits were obtained.For getting safty and highly purified limonene product,the various procedure effects on the extraction and purification were studied and the best procedure parameters were acquired.The results is:1.The d-limonene content in juices and peels of 90 different citrus varieties is analyzed by distillation titration.The results showed that different citrus juices have different limonene content.The d-limonene content in Sweet orange,Tangerine,Tangor and grapefruit juices is obviously different,whose average levels is 0.0824‰,0.2785‰,0.1063‰,0.0450‰respectively.In our experiments the d-limonene content of 9 concentrated juices and 15 fresh juices from company also had been studied,the results showed that concentrated juices have a very low limonene levels,the average content is 0.0018‰;and the average content of fresh juices is 0.1125‰.The d-limonene content in Sweet orange,Tangerine,Tangor and grapefruit peels is obviously different,whose average levels is 4.527g/kg,2.115g/kg,4.994g/kg respectively.It is found that after storage the limonene content in citrus juice and peels all decreased,and as well as found in different varieties of citrus from different harvest-period. 2.The differences of two extraction methods were studied,The parameters having effect on vacuum distillation extraction for food-grade limonene include vacuum, distillation time,distillation temperature.Take the cold-pressed orange oil as raw material,by orthogonalexperiment,the optimistic combination is:vacuum 0.08MPa, distillation time 10min,liquidte-mperature170℃.The concentration of limonene reached 95%.At the meantime,also the steadistillation technology for technology-grade limonene was studied,the parameters aredistillation temperature,distillation time. Taking Citrus Peels slurry as raw material,byorthogonal experiment,the optimistic combination is:distillation temperature 110℃,distillation time 45min.The concentration of limonene reached 95.46%.3.Taking food-grade Limonene as raw materials,the purification technology was studied.The 98.2%limonene was obtained by a process including the step of mixing d-Limonene with an oxidizer and separating the oxidizer from the d-Limonene,and then mixed with an acid and separated and finally with a wash water step.The optimistic combination:3%sodium hlorite- oxidants and 2%phosphoric acid.The concentration of limonene reached 90.38%.4.Supercritical Fluid Extraction-CO₂ technology was studied.The parameters having effect on d-Limonene extraction include extraction-temperature and extraction-time.By single factor experiments,it was found that the maximum d-Limonene will be extracted under the extraction temperature 55-60℃and the extraction pressure 8-10MPa.The parameters having effect on d-Limonene extraction by supercritical fluid extraction-fractionation include the extraction-pressure,extraction -time,extraction-temperature and temperature gradient.Taking citrus oil as raw material,by the orthogonal experiment,regarding the extraction rate as the index,the optimistic combination is:extraction pressure 8MPa,extraction temperature 60℃, extraction time 80min,the temperature gradient 40℃-55℃-60℃-65℃.The extraction rate reached 94.16%;regarding the content of limonene as the index,the appropriate combination is:extraction pressure 8MPa,extraction temperature 55℃,extraction time 80min,temperature gradient 40℃-55℃-60℃-65℃.The concentration reached 975.7μl/ mL.