Sorbic acid is a common food preservative that is used to prevent the growth of harmful bacteria and fungi. However, sorbic acid can contain impurities that may be harmful to human health. These impurities can include 2,4-hexadienoic acid, 2,4-heptadienoic acid, and 2,4-octadienoic acid. It is important to ensure that sorbic acid used in food products is free from these impurities and meets the necessary safety standards.