Edible items need to be moved to the top of the screen, and inedible items need to be moved to the bottom. If you release the object without bringing it to the desired part of the screen, then it will take the place where it would be without stopping its path. Leaving an item off the edge of the screen is considered a loss, and erroneous sorting is also considered a loss.
Grab the object with your mouse pointer (or finger on a mobile device) and move it to the top or bottom of the screen.