E101A - Riboflavin-5'-phosphate

At a glance

• What it is: The phosphorylated, water‑soluble form of vitamin B2 used as a food color and nutrient.
• E-number: E101A (often listed in EU rules as E101(ii)); related to riboflavin.
• What it does: Colors foods yellow to orange-yellow; also contributes vitamin B2.
• Where you’ll see it: Drinks, dairy-style products, soups and sauces, bakery and desserts, and fortified foods.
• Solubility: More water‑soluble than plain riboflavin, so it works well in beverages.
• Label names: “Riboflavin-5'-phosphate,” “riboflavin phosphate sodium,” “E101a,” or “E101(ii).”

Why is Riboflavin-5'-phosphate added to food?

Food makers use it mainly as a colorant to give a clean yellow shade, and secondarily as a source of vitamin B2 in fortified foods. Because the phosphate form dissolves better in water than plain riboflavin, it is especially handy for coloring and fortifying drinks and other high‑moisture foods.¹

What foods contain Riboflavin-5'-phosphate?

Riboflavin-5'-phosphate is authorized in the EU as a color in a wide range of foods, generally at “quantum satis” (use as needed, without a fixed maximum, provided good manufacturing practice is followed). Typical products include soft drinks, dairy and dairy‑analog drinks, bakery and dessert mixes, sauces, and cereals.¹

What can replace Riboflavin-5'-phosphate?

When formulators need a yellow/orange hue, common substitutes include:

• Curcumin from turmeric (warm yellow)
• Carotene or annatto (yellow to orange)
• Plain caramel (brownish yellow)
• Synthetic azo dyes like tartrazine or sunset yellow FCF where permitted

Swaps depend on desired shade, solubility, light/heat stability, and label preferences.

How is Riboflavin-5'-phosphate made?

Food‑grade riboflavins in the EU are specified either from fermentation (for example, using selected microorganisms) or by approved chemical routes. Riboflavin is then converted to its 5'-phosphate form—commonly the sodium salt—to improve water solubility and handling. The identity, purity, and manufacturing specifications for riboflavins, including the 5'-phosphate, are laid out in EU additive specifications.²

Is Riboflavin-5'-phosphate safe to eat?

The European Food Safety Authority (EFSA) re‑evaluated riboflavins (E101(i) riboflavin and E101(ii) riboflavin‑5'-phosphate) and found no safety concern at reported uses and use levels as food colors, and did not consider it necessary to set a numerical acceptable daily intake (ADI).¹ In EU law, riboflavins are permitted as colors under the general food additives framework and detailed specifications, which include purity criteria.²

Does Riboflavin-5'-phosphate have any benefits?

Yes. Riboflavin is vitamin B2, which the body uses to make the coenzymes FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide). These help enzymes release energy from food and support normal cell function, skin, and vision. When used in fortified foods, riboflavin‑5'-phosphate contributes to dietary riboflavin intake in the same way as riboflavin itself.³

Who should avoid Riboflavin-5'-phosphate?

There is no tolerable upper intake level (UL) set for riboflavin because of its low toxicity, and most people do not need to avoid it. Individuals under medical advice to manage vitamin B2 intake or with specific dietary restrictions should follow their clinician’s guidance and check labels.³

Myths & facts

• Myth: It’s a harsh synthetic dye. Fact: It is vitamin B2. Food‑grade material is produced under strict specifications, often by controlled fermentation, and may be used for both color and nutrition.²
• Myth: It’s different from “real” vitamin B2. Fact: The phosphate form is a vitamin B2 derivative that functions as riboflavin in the body.³
• Myth: It isn’t widely allowed. Fact: The EU authorizes riboflavins, including the 5'-phosphate, as colors in many food categories under good manufacturing practice.¹

Riboflavin-5'-phosphate in branded foods

On ingredient lists, look for “riboflavin-5'-phosphate,” “riboflavin phosphate sodium,” “E101a,” or “E101(ii).” If used mainly for nutrition, it may also appear near other added vitamins. If used for color, it may be grouped with other color additives. Placement varies by local labeling rules.

References

Footnotes

1. Re-evaluation of riboflavins (E 101(i), E 101(ii)) as food additives — EFSA Journal. https://www.efsa.europa.eu/en/efsajournal/pub/3357 ↩ ↩² ↩³ ↩⁴

2. Commission Regulation (EU) No 231/2012 — EU specifications for food additives (includes riboflavins, E 101). https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩² ↩³

3. Riboflavin Fact Sheet for Health Professionals — NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/ ↩ ↩² ↩³