Studies On Purification Of Garlic Essential Oil By Molecular Distillation

Garlic, Allium sativum L., is the perennial herb of lily family. Garlic essential oil is one of the functional components in the garlic. The sulfide in the garlic essential oil has distinct effects of pharmacology such as tumour-counteracting, vein-protecting, blood sugar-reducing and so on in which diallyl disulfide(DADs), diallyl trisulfide(DATs) are the primary components.The difference of components in the garlic essential oil extracted by hydrodistillation and SFE-CO2 was analysed by GC-MS. And the effects of temperature, pressure, feed rate, rotating speed and frequency on the molecular distillation were studied and the technologic condition of multi-molecular distillation was established. The main results were as follows:1. Difference of components in the garlic essential oil extracted by hydrodistillation and SFE-CO2It showed that DADs and DATs were distinct in garlic essential oil by hydrodistillation, in which the contents of DADs and DATs were 36.21% and 24.75% respectively. But DADs, 3-Vinyl-1,2-dithiacyclohex-5-ene and 3-Vinyl-1,2-dithiacyclohex-4-ene were found to be the characteristic flavor components in garlic essential oil by SFE-CO2, in which the total content of 3-Vinyl-1,2-dithiacyclohex-5-ene and 3-Vinyl-1,2-dithiacyclohex-4-ene was 33.25%. The relative contents of total sulfide composition of garlic essential oil by hydrodistillation were distinctively higher than that by SFE-CO2.2. A method for quantitative analysis of effective components of garlic essential oil by GCIt showed that the retention times of DADs and DATs were 11.212 min and 16.228 min respectively. This method reached to a higher precision (DADs 2.041% and DATs 4.805%) and recovery (DADs 100.449% and DATs 101.795%)3. The optimum conditions of fist-stage molecular distillationThe effects of distillation temperature, distillation vacuum degree, feed flow rate, rotator rate on the organic sulfide purity and yield were studied. On the basis of single factor experiments, the technological parameters were optimized by orthogonal tests that include 4 factors and 3 levels. The optimum condition of molecular distillation temperature, distillation vacuum degree, feed flow rate and rotator rate in first-stage were 50℃, 200Pa, 2.0mL﹒min-1, 200 rpm respectively.4. The technological conditions of the second-stage molecular distillationThe effects of disillation temperature and distillation vacuum degree on the organic sulfide purity and yield were studied. On the basis of single factor experiments, the technological parameters were optimized. The optimum conditions of molecular distillation temperature, distillation vacuum degree in second-stage were 45℃and 150Pa respectively.5. The technological conditions of the third-stage molecular distillationThe effect of disillation temperature on the variation trend of distillation quantity of DADs and DATs was studied. The technological condition of third-stage molecular distillation was distillation temperature 40℃and distillation vacuum degree 100Pa.6. The effects of distillation frequencyThe purity and yield of DADs and DATs were 85.03% and 54.35% obtained after 5 stages of molecular distillation.