Preparation and Structure Characterization of Ramulus mori Oligosaccharides Microcapsules with Antibacterial Activity

In order to reduce the hygroscopicity of Ramulus mori oligosaccharides, improve its stability and broaden the scope of application in product development, microcapsules of Ramulus mori oligosaccharides with good stability and inhibitory against Streptococcus mutans were prepared by spray drying using maltodextrin and whey protein isolate as wall materials. The antibacterial rate, hygroscopicity, molecular structure, microscopic morphology, thermal stability and storage stability of microcapsules were comprehensively evaluated. The results showed that the microcapsules had high antibacterial rate (61.31%±3.34%), low hygroscopicity (12.31%±1.47%) and small particle size (6.58±1.76 μm) when prepared by maltodextrin/whey protein isolate ratio 2:1 and the core/wall ratio 1:2. Scanning electron microscopy showed that the microcapsules had complete particle morphology and smooth surface structure. FITR showed that the microcapsules were formed by the electrostatic interaction between maltodextrin and whey protein, and the oligosaccharides were embedded into the microcapsules. X-ray diffraction analysis proved that the crystalline structure of Ramulus mori oligosaccharides microcapsules had been changed. The glass transition temperature of the microcapsules was 96.10 ℃, which was higher than the general storage temperature. What's more, the stability of Ramulus mori oligosaccharides was significantly improved at the temperature of 40.0, 60.0 ℃, and the humidity of RH 75.0%, RH 92.5% when embedded into the microcapsules. This research was expected to provide a theoretical basis for Ramulus mori oligosaccharides as functional ingredients.