Preparation And Application Of Mint Oil Microemulsion

Microemulsion of O/W type is an effective approach for envelop mint oil in attempt to obtain controlled, sustained and prolonged delivery of mint oil. Simple method was demonstrated to evaluate the encapsulation efficiency of mint oil microemulsion. The formulation and preparation method of mint oil microemulsion was developed. Herein, the stability of mint oil microemulsion was also evaluated. Furthermore, the solidification of mint oil microemulsion by porous starch was investigated. Finally, the studies on the application of mint oil microemulsion and its solidification in tobacco were determined.Static HS-GC, SPEM-HS-GC and spectrofluorimeter were employed to analysis the un-encapsulated mint oil. When 2μL of mint oil was equilibrated for 30min at 60℃, the encapsulation efficiency of mint oil microemulsion was 78%. The 4μL solution of mint oil, ethanol and water preheated for 10min and extracted by CAR/PDMS-75μm fibre for 40min at 40℃, result of encapsulation efficiency of mint oil microemulsion was 67%. Fluorescence spectra had a good linearity correlation with spectrofluorimeter over a range of 0 120μg·L^-1 for pyrene concentration in water (R2=0.9986) and the encapsulation efficiency evaluated by Spectrofluorimeter was 79%. Compared upon three methods, Static HS-GC has proved to be convenient, sensitive and accurate.Influence of surfactant type and processing parameters on the formation of MO-MEs were studied by comparing the area of monophase ME regions in pseudoternary phase diagrams, mixed surfactants of AOT and Cremophor EL at 1:1 ratio, S/CS=1:1, processing temperature of 30℃and addition order of mint oil+ water+ mixed surfactants were found to be the most effective ones. Microemulsion types within the momophase region were analyzed by conductivity measurement and dye and the modified phase diagrams showed the optimal formulation for the mint oil microemulsions: mint oil/ AOT/ Labrasol/ ethanol/ water= 12:7:7:14:60 (w/w). As tested with dynamic light scattering and TEM, the microemulsion employing the optimal formulation and preparation parameters had 98%(v/v) homogeneous shape with particle size ranging from 9 38nm, and average particle size was about 20nm. After storage at room temperature for twelve months, the encapsulation efficiency of mint oil microemulsion was greater than 77% with retention ratios higher than 90% and average particle size remain around 20nm. The results indicated that the optimized formulation of mint oil microemulsion may be a promising vehicle for the protection of mint oil. The oral LD₅₀ in rats was 7.94g·kg_bw^-1 and 95% convinced ranges of LD₅₀ were 4.89 12.90 g·kg_bw^-1, indicated that mint oil microemulsion was one of non-toxic substances.Oil absorption capacity and yield of porous starch was taken as criteria, optimization of the preparation of solidified mint oil microemulsion with porous starch was achieved by single factor experiments. The best preparation parameters was as follows: Mixed enzymes (α-amylase/glucoamylase=1:2, enzymatic activity was 547.6 and 948 IU·mL^-1) was added by 0.75% (v/v) into corn maize starch solution (starch: buffer=1:5, w/w, pH=4.5), incubated at 45℃for 10h. The obtained porous starch was blended with mint oil microemulsion at 5:1(w/w), adsorbing for 1h at room temperature and vacuum dry at 40℃for 24h. Encapsulation efficiency of solidified mint oil microemulsion with porous starch was evaluated by Static HS-GC, of which result was 18% higher than that by microemulsion alone. Compared with mint oil microemulsions, solidified microemulsion by porous starch showed more controlled and stable. Finally, smoking machine and sensory panel tested showed sustainable release of mint oil during cigarette burning after microemulsification and porous starch solidification.