Abstract Sandwiches are widely consumed, yet the mechanics of bread–filling interaction during biting remain unstudied. Texture mismatch can cause filling loss, high bite force, and poor eating experience. We developed a model system using toasted breads of varying firmness and fillings spanning a range of yield stresses, alongside common breads and fillings. Bread indentation hardness and filling apparent yield stress were quantified mechanically, and a custom bite rig simulated standardized bites to measure filling delivery, spillage, and peak bite force. From these data we defined a stress shielding ratio and a composite YUM Score capturing filling retention per unit bite force. Stiff breads paired with runny fillings performed worst, exhibiting high stress shielding, low delivery, and greater spillage, while well-matched bread–filling pairs achieved superior efficiency. Real sandwiches generally followed similar trends. These results show that minimizing stiffness mismatch, a core materials principle, improves sandwich performance and eating satisfaction.
Schudel et al. (2026) studied this question.