The reaction produces iron hydroxide. Official website of Huaxi Hospital introduced that sodium propionate is a colorless transparent crystal or granular crystal powder, which is used as a food preservative, a preservative in cakes and a bread mildewproof agent. Sodium propionate is almost non-toxic to human body, and reacts with oxygen and water to generate iron hydroxide to absorb the oxygen in the packaging bag, thus prolonging the shelf life of food.