PCATALOG
Mannitol Is a Good Anticaking Agent for Spray-Dried Hydroxypropyl-Beta-Cyclodextrin Microcapsules
Pubdate：2024-01-12 Click：70
Agglomeration is an undesirable phenomenon that often occurs in spray-dried microcapsules powder. The objective of this work is to determine the best solution for spray-dried hydroxypropyl-β-cyclodextrin (HP-β-CD) microcapsules from four anticaking agents, namely calcium stearate (CaSt), magnesium stearate (MgSt), silicon dioxide (SiO2), and mannitol (MAN), and to explore their anticaking mechanisms. Our results showed that MAN was found to be the superior anticaking agent among those tested. When the MAN ratio is 12%, the microcapsules with a special Xanthium-type shape had higher powder flowability and lower hygroscopicity and exhibited good anticaking properties. Mechanism research revealed that CaSt, MgSt, and SiO2 reduce hygroscopicity and caking by increasing the glass transition temperature of the microcapsules, while MAN prevents the hydroxyl group of HP-β-CD from combining with water molecules in the air by a crystal outer-layer on the microcapsule surface.
Keywords:
spray drying; microcapsules; mannitol; crystallisation; caking
Conclusions
This study showed that MAN was the superior anticaking agent among those tested, including CaSt, MgSt, and SiO2. Microcapsules with anticaking agents exhibited a lower moisture content, hygroscopicity, angle of repose, and HR than HP-β-CD microcapsules without a caking agent. CaSt, MgSt, and SiO2 reduced hygroscopicity and caking by increasing the glass transition temperature of the microcapsules. In contrast, the anticaking effect of MAN can be attributed to the hygroscopicity of HP-β-CD being hindered by the crystallisation of MAN. In addition, microcapsules with higher MAN ratios showed lower hygroscopicity and higher powder flowability. However, MAN ratios of 16% and 20% caused the undesirable ‘hard agglomeration’ of HP-β-CD/MAN microcapsules. Considering all tested properties, a 12% MAN ratio provided the optimal HP-β-CD/MAN microcapsule with high powder flowability and low hygroscopicity, reflecting excellent anticaking properties. Notably, the microcapsules exhibited a special Xanthium-type morphology. During spray drying, the concentration of MAN and HP-β-CD increased continuously with moisture evaporation. Given the higher solubility of HP-β-CD, it tended to migrate to the inner layer of the droplet. Conversely, the relatively low solubility of MAN led to its migration to the outer layer of the droplet, where it formed crystals as the concentration became saturated. Thus, the crystallisation of MAN hindered the agglomeration of microcapsules owing to the moisture absorption of HP-β-CD.
