Impact of trehalose on physicochemical stability of β-carotene high loaded microcapsules fabricated by wet-milling coupled with spray drying

Solvent-free β-carotene high loaded microcapsules formulated by octenyl succinic anhydride (OSA)-starch and trehalose were prepared by a combination of wet-milling and spray drying. The influence of different mass ratios of OSA-starch to trehalose on the particle size distribution, storage stability, hygroscopicity and redispersibility of β-carotene microcapsules was investigated. The optimized microcapsules exhibited a small average diameter (228.2 nm) after rehydration with high encapsulation efficiency and loading capacity (99.06% and 10.32%, respectively). The phase separation in the OSA-starch and trehalose composite matrix was observed in the presence of trehalose at a high level, which was favorable for the prominent storage stability of β-carotene (96.16% for 50 days). The half-life of rehydrated β-carotene microcapsules was also extended by 2.23- and 1.25- folds during the thermal- and photo-degradation treatments. The crystallinity of β-carotene microcapsules was largely reduced due to the enhanced hydrogen bonding interaction between OSA-starch and β-carotene as analyzed by FTIR. SEM images showed that the morphology of β-carotene microcapsules was regulated by the level of trehalose. Confocal Raman spectrum microscopy and hygroscopic variation jointly verified the entrapment of β-carotene into a glassy matrix formed at a high level of trehalose. Moreover, a high level of trehalose could improve the spontaneous sinkability and dispersibility of β-carotene microcapsules, which were completely rehydrated in less than 1 min.