| Micro-algal Oil is the functional oil which is abstracted from marine unicellular algae, whose main functional active components are polyunsaturated fatty acids which have important physiological function, such as linolenic acid,arachidonic acid,docosahexaenoic acid (DHA) and so on. Compared to deep-sea fish oil, its fatty acid composed more simply and poor in EPA which inhibits the growth of infants. So the Micro-algal Oil is more safe for pregnant women,lactating women,infant and children. But the DHA in Micro-algal Oil belongs toω-3 PUFAs. It is unsTab because of light, heat, oxygen.and it can be oxidized easily, which make the property of nutrition healthcare and physiological activity lose. Therefore, it should be settled immediately that improving the stability of micro-algal oil. It is a key question to study on the stability of Micro-algal Oil. Micro-algal Oil Microcapsule can protect its DHA effectively.Response surface experiments designed by Box-Behenken were conducted in our work to optimize the wall-materials of micro-algal oil microcapsules. On the basis of single-factor test with the content of emulsifier, casein, cyclodextrin, and core material, the response surface experiments with four factors and three levels was designed. By comprehensive analysis of the obtained linear regression equation and the operational cost, the ultimate conditions were selected as follows:emulsifier 3.98%, casein 3.52%, cyclodextrin 11.1%, and core-material loading 30%. Using the formulation predicted above, the actual encapsulation efficiency of the microcapsules could reach 93.37%.The storage stability of the micro-algal oil microcapsule was investigated by determining the physicochemical properties. The results were as follows:the moisture content, the encapsulation efficiency, the average particle size and the solubility of the samples were 3.68%,94.30%,497.9 nm and 94.37%, respectively. And all of them were relatively stable during the storage period. The infared spectrum indicated that the original structure and nutritive value of micro-algal oil can't be destroyed by microencapsulation. The results of SEM also confirmed that the core material can be protected by microcapsulated technology. The high Tm of the microcapsule was observed by DSC and TG. The structure of microcapsule could be exist stably during most productions. Though the thermal stability of the microcapsule declined during storage, there was no obvious change. With the temperature increasing, the damage rate of microcapsule increased in the test of heat resistant strength, which suggested that microcapsule should be stored at lower temperature.The stability of the self-made microcapsules was determined by measuring the peroxide value (POV) and DHA retention ratio in different conditions of light, temperature and humidity, taking the purchased microcapsules as the control group. At the same time, the Avrami's equation was used to providing kinetic parameters such as release mechanism parameter and release rate constant (K). The results indicated that the POV and K of the two kinds of samples increased as the intensity of the conditions enhanced. While the temperature and light tolerance of the self-made samples were better than that of the purchased ones. However, the self-made ones were very sensitive to humidity, the POV and K increased obviously as the humidity-increasing, after 12d's storage at 90% humidity, the DHA retention ratio and POV were 3.45% and 18.92 meq/kg, respectively.Through investigating the effects of the changes of DHA content during the making process of micro-algal oil microcapsule, the optimum addition level of algal oil in the milk powder was 0.426% in order to ensure 0.5% DHA in the total fatty acids. The retention rate of DHA in the formula milk powder was 91.06% after storage for 360 days under vacuum packing and dark condition. It shows that the product still has high retention rate of DHA after a year.
|
PDF Full Text Request