The Study On Microcapsule Preparation Of Lutein And Its Stability

Lutein is a kind of natural pigments with strong colouring power, rich nutrition and health care role. As the number of conjugated double bonds it has vivid color and inhibiting ability of free radicals, which in recent years has been widely used in food and pharmaceutical industries. However, due to unstable and vulnerable to light, oxygen and other environmental conditions which accelerate degradation, its applications are limited greatly. In recent years, as microencapsulation can protect the sensitive components from the external conditions, the microencapsulation technology developed rapidly in the food industry. Coacervation microencapsulation method is the classic method with simple operation, suitable for insoluble drugs or food. In this paper, microcapsules of lutein were made with complex coacervation method in order to raise the stability of lutein and make it more convenient in storage and applications.In this paper, lutein was microencapsulated using complex coacervation of gelatin and gum arabic. The preparation processing, physical and chemical properties and storage stability were studied. Main contents and results are listed as follows:The technological parameters were investigated using single factor experiments:the wall material concentration is 0.5%-1.5%, core-wall ratio is 2:1-1:2, reaction temperature is 40℃-50℃, pH value is 4.1-4.7.On the basis of single factor experiment, response surface analysis was used to optimize the process conditions including three independent variables the wall material concentration, the ratio of core material to wall material, and the pH value. The optimal conditions were obtained for the lutein microencapsulation by complex coacervation method:wall material concentration 1.0%, the ratio of core material to wall material wall 1.25:1, pH value of 4.2. The theoretical optimal embedding rate was 86.41%, the embedding rate in practice by verifying was 85.32%±0.63%.The physical and chemical properties of lutein microcapsules were investigated using Laser particle size analyzer, FT-IR spectrum, scanning electron microscope (SEM), differential scanning calorimetry (DSC). The results showed that particle size of microcapsules was widely distributed in the range 0-30μm, and the average volume diameter was 14.198μm. It was proved the coacervate was formed by the physical interaction between gelatin and gum arabic using FT-IR spectrum, not chemical interaction. Glass transition temperature (Tg) of lutein microcapsules by DSC was at 40.5℃which indicated it had good storage stability.The influence of light, temperature, oxygen and relative humidity on the stability of lutein microcapsules was studied. Microcapsules products stored stably in low humidity (relative humidity=33%), when relative humidity rised to 80% or above, the reservation rate was decreased dramatically. Compared with the condition in light, the losing rate of lutein in light-proof condition was lower. Lutein microcapsules were stable in in 4℃,25℃, but the stability was reduced in 50℃. Compared with the condition in the presence of oxygen, the losing rate of lutein decreased in absence of oxygen.