Why do mushrooms in vinegar squeak?

Mushrooms in vinegar can produce a squeaking sound due to the interaction of the vinegar with the water and air pockets within the mushrooms. When you bite into or chew the mushrooms, the pressure causes these air pockets to collapse, releasing the trapped air and creating a squeaking noise. This phenomenon is more pronounced in certain types of mushrooms that have a spongy texture. The acidity of the vinegar may also enhance this effect by altering the mushroom's structure slightly.