| Conjugated linoleic acid(CLA) is an active substance with multiple physiological functions. However, CLA has a strong activity because of the special conjugated double bonds, therefore its applications are limited by instability, being oxidized easily and other defects. More importantly, the best absorption site of CLA is small intestine. This paper aims to use octenyl succinic anhydride modified starch(OSA starch) and xanthan gum as a complex carrier of CLA, protecting it and reducing its losses in the stomach(non-absorption site of CLA) and improving its utilization in intestinal tract of humans. The main contents of research are as follows:Firstly, the emulsion of which OSA starch-xanthan gum complex carrier acts as aqueous phase, CLA acts as dispersed phase was prepared. The rheological properties, particle size, stability of emulsion were studied. The solids contents of emulsion and ratio of OSA starch and xanthan gum in wall materials(wall material compound ratio) were initially identified. After comprehensively analyzing of the above factors, the solid content of emulsion were determined to be 5~20 g/100 g, wall material compound ratio to be 1:100~1:60.Secondly, CLA microcapsules were prepared by spray drying. The interaction between OSA starch and xanthan gum are measured by FTIR, the result showed that no new complex groups appeared and there was only hydrogen bonding between them. By further optimizing the preparation process, the final process parameters were determined as the ratio of core material and wall material 1:4, the solids content of emulsion 10 g/100 g, inlet air temperature 160°C. Then changing wall material compound ratio(1:60, 1:80, 1:100 and 0:100(control), the mass ratio) to prepare four microcapsules. The encapsulation efficiencies were all higher than 97%(w/w), indicating that CLA effectively entrapped within the internal structure of the microcapsules. Laser particle size analyzer showed that the median diameter of the particles increased significantly with the increasing amount of xanthan gum. Besides, specific surface area of microcapsules was the largest when the wall material compound ratio was 1:100. The microstructure of the microcapsules was observed by scanning electron microscope. The microcapsules had intact particle morphology and different degree shrinkage on the surface, which was consistent with the typical characteristics of the spray dried microcapsules.Finally, the thermal stability, oxidation stability, CLA release characteristics of the microcapsules in-vitro and in-vivo were studied. The thermal stability of the microcapsules and wall material were analyzed by thermal analysis system. The results showed that xanthan gum in the wall material could improve its thermal stability, microcapsules behaved the high thermal stability under operating temperature(100°C~160°C) of the spray-drying, thermal degradation did not occur. Oxidation protection was determined by headspace gas chromatography. It confirmed that microencapsulation significantly improved the stability of CLA against oxidation, and anti-oxidative stability of the microcapsule increased with the addition of xanthan gum in wall material. CLA cumulative release percentage in simulated gastric fluid was very low-between 3.6% to 6.1%(w/w). A positive correlation was observed between the extent of microcapsule stability and the proportion of xanthan gum in the wall material. The small intestine simulation results showed CLA release percentage was between 12.1%~50.1%. An increase in the proportion of xanthan gum could enhance the ability of wall material to protect CLA, making it harder to release the CLA in simulated small intestine. Fluorescently labeled tracer method was taken to study the transportation of CLA in the digestive tract of animals indirectly. It was proved that CLA was rarely released in the stomach of rat, but majority of CLA was released into the small intestine, demonstrating good property of controlled release. |
PDF Full Text Request