Riboflavin
The short version
Vitamin B2 — used both as a yellow-orange colorant and as a nutritional fortifier.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Isolated from milk whey in the 1920s; structure elucidated by Richard Kuhn (Nobel Prize 1938) and Paul Karrer. Commercial production today is mostly by fermentation of microorganisms (Bacillus subtilis, Ashbya gossypii) on plant-derived substrates.
How it's used
Used to color sauces, cereals, dairy desserts, and ice cream a soft yellow-orange. Also added to fortified flours and supplements to meet nutritional B2 needs. Riboflavin-5'-phosphate (E101(ii)) is more water-soluble and is used in clear beverages.
Safety profile
No ADI required — essential nutrient. Excess is excreted in urine, producing the characteristic bright yellow color. Considered safe at any food-relevant level.
Physical & chemical properties
Yellow-orange crystalline powder, sparingly soluble in water (the phosphate form is more soluble). Fluorescent under UV. Sensitive to light — can degrade quickly in clear-glass packaging.
Regulation worldwide
Permitted globally without restrictive limits for food use.
Educational information only. Not medical or dietary advice.