Inedible Azo Dyes and Their Analytical Methods in Foodstuffs and Beverages

Edible colorants, as an important part of food additives, can not only enhance the sensorial attributes of foodstuffs, but can also increase one's appetite. They hold a very important position in food processing. In the past decades, the illegal addition of the inedible colorants has become one of the major issues of food safety. Industrial dyes, especially some azo dyes, are illegal additives frequently found in foodstuffs. They cannot provide any nutrients for the human body and even have toxicity, carcinogenic, or mutagenic effects, which may cause serious damage to consumers' health. There is an increasing demand to detect the inedible azo dyes in foodstuffs for health and safety reasons. In this review, the types and the physicochemical properties of the inedible azo dyes adulterated in foodstuffs and beverages are summarized, and the emphases are focused on the sample pretreatment methods and analytical techniques for monitoring of these dyes in foodstuffs and beverages.