How tooth loss and food texture impair egg white gel digestion in the elderly: Insights from the integrated bio-inspired oral mastication simulator and dynamic human stomach-intestine system.

Traditional static in vitro digestion models neglect the critical role of oral processing, leading to poor physiological relevance, particularly for vulnerable populations such as older adults with impaired chewing function. Here, we present a closed-loop system that couples a bio-inspired oral mastication simulator (iBOMS-III) with a dynamic human stomach-intestine system (DHSI-IV), replicating the complete sequence of mechanical chewing, bolus formation, gastric emptying, and intestinal digestion under physiologically relevant conditions. Using egg white gels (EWG) cooked at 75 °C (soft, 75-EWG) and 95 °C (firm, 95-EWG) as model protein foods, we simulated declining masticatory capacity in the elderly with 3D-printed dental molds representing intact dentition (M0T), loss of 3 teeth (M3T), and loss of 6 teeth (M6T). Progressive tooth loss dramatically reduced masticatory performance: median bolus particle size (d₅₀) increased from 1.40 mm (M0T) to 2.05 mm (M3T) for 75-EWG and from 2.13 mm to 2.67 mm for 95-EWG. This larger particle size directly delayed gastric emptying (dry-matter half-time t₁/₂ lengthened from 105 to 117 min for 75-EWG and from 147 to 169 min for 95-EWG) and significantly lowered terminal small-intestinal protein hydrolysis after 3 h of digestion, with free amino acid release dropping from 50.1 to 39.9 mg/g (75-EWG) and from 40.6 to 29.8 mg/g (95-EWG). These findings demonstrate that both impaired mastication due to tooth loss and increased food hardness synergistically hinder bolus breakdown, delay gastric transit, and reduce protein hydrolysis in the elderly. The integrated iBOMS-III/DHSI-IV platform represents a promising in vitro tool that reliably replicates the entire upper gastrointestinal process, offering unprecedented physiological fidelity for designing texture-modified, digestion-friendly foods tailored to older adults.