Preparation of gelatin/sodium carboxymethyl cellulose-based probiotic controlled-release tablets via complex coacervation and the double emulsification method

To increase the survival and controlled-release properties of probiotics during storage and gastrointestinal digestion, this study develops a novel probiotic intestinal-targeted controlled-release tablet using a gelatin/sodium carboxymethyl cellulose (CMC)-based complex coacervation and double emulsification method integrated with spray drying and direct compression technology. The effects of three different CMCs on the complex coacervation process, as well as the microstructure, physicochemical characteristics, gastrointestinal controlled-release behavior, and storage stability of the resulting microcapsule tablets, were systematically evaluated. The results demonstrated that the complex coacervates formed from medium-viscosity CMC and gelatin exhibited the highest probiotic encapsulation efficiency (EE) (87.27%) in the double emulsion system. Following spray drying, the microcapsule powders exhibited favorable physicochemical properties. Second, the microcapsule tablets formulated with medium-viscosity CMCs provided the most effective protection for probiotics, with a survival rate of 48.74%, which was significantly higher than that of the unencapsulated tablet group (21.09%, p < 0.05). These advantages can be attributed to the moderate molecular chain length and steric hindrance exhibited by medium-viscosity CMC, which enable the coacervate to achieve sufficient emulsification performance and protective capability. In simulated gastrointestinal digestion experiments, the survival rate of probiotics in the microcapsule tablets at the end of intestinal digestion ranged from 75.41% to 85.68%, which was also markedly higher than that of the unencapsulated group (11.46%, p < 0.05). Furthermore, after storage at 37°C for six months, the viable bacterial count in the microcapsule tablets decreased by only 0.9×10 9 to 1.57×10 9 CFU/tablet. This study systematically investigated the impact of CMC viscosity on the encapsulation and controlled-release performance of a gelatin/CMC (G/CMC) complex coacervation system, leading to the successful development of a probiotic controlled-release tablet with high survival rates, enhanced stability, and targeted delivery.