Is e921 vegan?

E921 is the additive code for L-cystine, a non-essential amino acid used primarily as a dough conditioner and flour treatment agent in commercial baked goods. It modifies gluten structure to improve the elasticity and handling of dough, and it also appears in certain nutritional supplements and processed savory flavorings. Manufacturers produce L-cystine either through the extraction of keratin from animal proteins, chemical synthesis, or microbial fermentation using plant-derived carbohydrates.

This ingredient is classified as possibly vegan because product labels rarely indicate whether the source is plant or animal. Animal-derived L-cystine is traditionally extracted from duck feathers, poultry waste, or hog hair. Plant-based alternatives are generated through bacterial fermentation from glucose or through synthetic production methods. Because standard packaging does not differentiate between these origins, confirming that a product is vegan requires checking for an official vegan certification on the package or contacting the food manufacturer directly.