Preparation Of β-carotene Microcapsules And Their Stability

The results of some recent studies indicated that as a food additive, because of its possible good biological effect on human health, p-carotene has been used in the precaution and curation of many diseases frequently. However, for the existence of many double bonds in its molecular structure, the degradation and isomerization of P-carotene will speed up as a result of the exterior surroundings' influence, such as temperature and illumination. Thus, in order to improve the stability of P-carotene, making it easy to store and transport, microencapsulation technology has been applied to prepare P-carotene microcapsules.First, Spray-Starch-Fluidized-bed-Drying and Freeze-Drying were used to prepare the P-carotene microcapsules respectively. Then, the process of preparation and the quality of products were compared. The results showed that although freeze-dried powder had better encapsulation field and stability;spray-dried powder was more uniform and orbicular with shorter production cycle. In short, nowadays the latter is still more applicable to the industrial producton of p-carotene microcapsules.Based on the comparison of the spray-dried powders' encapsulation yield (EY), encapsulation efficiency (EE) and storage stability (SS) which was studied at different temperature under visible light, the gelatin (50PS) was chosen to be the primary wall-material. Then p-carotene was encapsulated in a wall system consisting of different ratios of gelatin (50PS), sodium caseinate and acacia. Through the same comparison process, the powder with gelatin: sodium caseinate (2:1) as wall material was selected for its good values of EY, EE and SS.In order to know the effect of exterior surroundings such as oxygen, temperature, illumination and relative humidity on the degradation and isomerization reaction of P-carotene microcapsules, the changes of stability of some powders and crystal were studied at in different storage conditions. It can be concluded that the application ofmicrocapsule technology could greatly improve the stability of P-carotene;oxygen could accelerate the degradation of P-carotene greatly;in the range from 25 to 55 °C, the effect of temperature on P-carotene was not remarkable as expected;the higher the illumination intensity, the larger the degradation rate of p-carotene;when relative humidity is larger than 50%, the degradation rate of crystal increased as the increasing of relative humidity, that of powders with gelatin as primary wall material decreased at the same time.At last, RP-HPLC was explored and set up to separate and detemine cis- / trans-isomers of p-carotene in its microcapsules. A mobile phase of methanol-methylene chloride (99:1) with a sample solvent of methonal-chloroform(45:55) was chosen to separate the isomers of p-carotene in powders which had been stored in refrigeratory for a period of time. The results showed that the amount of all-trans-P-carotene decreased largely;of 15-cis isomer decreased a little;of 9-cis and 13-cis isomers increased a little;the increasing amount of 13-cis isomer was higher than that of 9-cis isomer;and it's hard to detect 13,15-di-cis-P-carotene.In conclusion, according to the research results of the stability of P-carotene microcapsules, all of the degradations of the total amount of all-trans and cis forms of p-carotene during storage fit a first-order model. In order to prolong their half life, the p-carotene microcapsules should be stored at low temperature(4°C), low relative humidity and in dark, airproof or vacuum conditions.