Optimizing 3D-printed core-shell hydrogel system for probiotic protection: stability under in vitro digestion conditions and during storage

This study aimed to develop a novel pH-sensitive core-shell delivery system to improve probiotics' viability during simulated digestion and storage. A 10-strain premix of Lactobacillus and Bifidobacterium was encapsulated within a pregelatinized starch-based gel core, while alginate/pectin (Al/P) gel was employed as the shell using a 3D food printing (3DFOODP) process. The survival rates indicated that the 3DFOODP process did not compromise probiotic viability. To evaluate efficacy, a long-term storage stability study was conducted over a 33-day period under 4 °C and 23 °C, and at 50 °C for 2 h. Storage at 4 °C was most favorable, maintaining a survival rate of 64.37% after 33 days. In contrast, unencapsulated probiotics exhibited significantly reduced viability, falling below 5% by day 18 at 4 °C (3.55%) and by day 15 at 23 °C (2.75%), and reaching negligible survival by the end of the 33-day storage period. Under simulated digestion, the retention of encapsulated probiotics was 97.22% in the oral phase, 83.33% under gastric conditions, and 82.70% in the intestinal phase. Conversely, unencapsulated probiotics showed 93.62%, 10.92%, and 6.30% retention, respectively. These findings provided strong evidence supporting the protective function of the core-shell gel system, thereby facilitating the targeted functionality and colonization.