Microwave drying induced 4D-printed elderly dysphagia diet with Tremella fucitormis

Although Tremella fucitormis is a kind of nutritious edible fungi, wildly accepted by the public, its original elastic texture and appearance are not suitable for the growing elderly people with dysphagia. This work aimed to use microwave drying to fabricate suitable appearance and textural properties of 4D printed nutritious Tremella fucitormis-based food with high shape fidelity for the elderly people with dysphagia, considering the amount of sodium alginate addition (0.86%, 0.97%, 1.08%, 1.18% and 1.29%), and the microwave drying duration (0, 10, 20, 30 and 40 s). Results showed that sodium alginate addition obviously increased the apparent viscosity, hardness, elasticity, chewiness, adhesion, cohesion and shape stability of such foods; however, higher flow behavior showed negative impact. The sample with 1.08% sodium alginate exhibited the best shape fidelity (>95%). As the microwave drying duration increased, the deformation degrees of the printed flower with four petals simultaneously increased, showing an expected deformable 4D printing “blooming” behavior. Morphological differences between printed and cast samples suggested that, to the preparation of such highly viscoelastic materials, microwave drying and 4D food printing was helpful. International dysphagia diet standardization initiative (IDDSI) tests indicated that such food could be classified as level 5-minced and moist diet, which was suitable for people with dysphagia.