The scientific name for baking soda is sodium bicarbonate. It is a weak base that can act as an acid depending on what it comes in contact with. The smells in your fridge are made up of food particles that float around and eventually settle into your other meals. Putting a box of baking soda in your refrigerator gives those smelly particles something other than your leftovers to bond with. The unique characteristics of sodium bicarbonate make it very attractive to both acidic and base particles, once these particles bond with the baking soda the odor is neutralized. Just remember while baking soda is used in many recipes, you should not cook with baking soda that has been used to neutralize odors. Part of the neutralization process means the baking soda has absorbed the food particles, which does change the taste of the baking soda.