Ultra-Fast Wetting of the Fresh Popcorn

Without chewing, the fresh popcorn dissolves immediately upon being put in the mouth. Such good taste decay dramatically with increasing the exposure time in air, especially in humid air. However, the involving mechanism of the saliva wetting the popcorn remains unclear. Here, it is revealed that the ultra-fast wetting property of the fresh popcorn is the key for its good taste. For the fresh popcorn, the unique 3D throughout micro-porous structure facilitates capillary flows both in-plane and off-plane at micro-/nano- scale, and the water-soluble crystalized starch further prompts the water spreading, which cooperatively leads to an immediate structural collapse. The unique ultra-fast wetting of the fresh popcorn is therefore featured as the wetting with dissolving. After cooling down, the crystalized starch changes gradually into an insoluble amorphous state by absorbing water molecule, as is confirmed by the in situ XRD and infrared spectroscopy. As a result, the ultra-fast wetting decays drastically with prolonging the in-air exposure time, as well as the taste, which makes immediate cooking vital for the good taste. It is demonstrated that heating can partially restore the ultra-fast wetting. It is envisioned that the result will inspire the innovative micro-fabrication of various starch food by engineering the starch crystalline structure.