Is unflavored gelatin supposed to smell bad?
Simply so, does gelatin taste bad?
All of them smell bad, but as a general rule they don't taste bad when used in something. I did notice a faint taste to the Great Lakes gelatin in the gummies, but it wasn't overpowering. Knox gelatin is the strongest of the three.
Hereof, why do marshmallows smell bad?
If your common store-bought marshmallow has any smell at all, it'll typically be a meager whiff of imitation vanilla. The other ingredients are gelatin and a few types of sugar, and those don't tend to have strong scents. “Upscale” or home-made marshmallows may have a deeper aroma depending on ingredients, though.
At room temperature, it is a solid. Heat it up to body temperature, and it becomes a liquid. So, when you eat it, it literally melts in the mouth. When you heat the gelatin up, these bonds between the chains loosen, turning the chemical into a liquid as they slide away from each other.