E101 (ii) Food Additive: What It Is, Safety & Uses

You are reading an ingredient label on a multivitamin drink, a fortified cereal, or an energy product and you see E101 or E101(ii) listed. Most people scan past it. Some stop and wonder what it actually is, whether it is safe, and whether it belongs in food at all.

This post answers all of that clearly, in one place.

The Short Answer

E101(ii) is riboflavin-5'-phosphate sodium. It is the water-soluble, active form of vitamin B2, used in food both as a natural yellow colorant and as a nutrient source. It is derived from riboflavin and is considered safe by every major food safety authority in the world.

It is not an artificial chemical. It is a phosphorylated form of a vitamin your body already makes and uses every day.

Understanding the E101 Group

The E101 designation covers a group of riboflavin-based compounds authorised as food additives in the European Union. The E101 group contains two sub-types: E101(i), which is riboflavin (plain vitamin B2), and E101(ii), which is riboflavin-5'-phosphate sodium.

E101(ii) is also sometimes referred to as E101a in older documentation. Outside the EU, the same compound carries the INS number 101(ii) under the Codex Alimentarius system used internationally.

The two forms are closely related but not identical. E101(i) (plain riboflavin) has low water solubility, which limits its use in liquid applications. E101(ii) (riboflavin sodium phosphate) is significantly more water-soluble, which is why it appears more frequently in beverages and liquid formats.

What Does It Actually Do in Food?

E101(ii) serves two roles simultaneously, which is relatively unusual for a single additive.

As a colorant, it imparts a natural yellow to orange-yellow colour. The food dye riboflavin is often responsible when foods look yellow — appearing in products such as puddings, cake fillings, biscuits, mayonnaise, ice cream, and cooking oil. Multivitamin drinks and tablets also contain the same substance, declared as vitamin B2. As a nutrient, it contributes to the vitamin B2 content of the product. Riboflavin is an essential component of two major coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which play major roles in energy production, cellular function, growth, and development, and metabolism of fats, drugs, and steroids.

This dual function makes E101(ii) particularly practical for manufacturers of fortified foods and beverages, where meeting nutritional claims and achieving a consistent yellow colour can be done with a single ingredient.

Where You Will Find It

Riboflavin can be used to colour convenient foods, soft drinks, cheese and cheese products, dairy products, bakery goods, fish products, canned fruits and vegetables, confectionery, dessert powders, sherbets, jams and jellies, soups, mayonnaise and salad dressings, fats and oils, mustard, and flavorings.

Beyond food, E101(ii) also appears in dietary supplements, particularly in multivitamins and B-complex products where the active phosphorylated form of B2 is used instead of plain riboflavin. It is not permitted in foods intended for infants and young children.

Is E101(ii) Safe?

Yes, and this has been evaluated thoroughly at the regulatory level.

In the EU, riboflavins are authorised food additives at quantum satis in all foodstuffs, with the exception of aromatized wines and aromatized wine-based drinks where concentrations are capped at 100 mg/L. EFSA conducted a full re-evaluation in 2013 and allocated no numerical ADI, meaning there is no established upper limit of concern when used as intended. JECFA assigned a group ADI of "not specified" for riboflavin and related riboflavin sources at its 92nd meeting in 2021.

A "not specified" ADI from JECFA is the highest possible safety classification. It means the available evidence does not identify a level of concern that requires a numerical cap.

EFSA's 2013 scientific opinion noted that riboflavin-5'-phosphate sodium is rapidly dephosphorylated to free riboflavin in the intestinal mucosa and is then metabolised using normal metabolic pathways. The committee found no adverse effects in 90-day rat studies and concluded that riboflavin and riboflavin-5'-phosphate do not raise concerns with respect to genotoxicity.

Normal doses are considered safe during pregnancy. Riboflavin is a water-soluble vitamin, meaning excess is excreted through urine rather than accumulating in tissue. This is also why high intakes produce bright yellow urine, a well-known and harmless effect.

E101(ii) vs E101(i): What Is the Difference?

Both are forms of vitamin B2 authorised as E101.

For solid dose applications where solubility is not a constraint, E101(i) is commonly used. For beverages, liquid formulations, and any application requiring meaningful dissolved concentration, E101(ii) is the practical choice.

For a full technical comparison of the two forms, see our post on Riboflavin 5-Phosphate vs Regular Riboflavin: What's the Difference?

Is E101(ii) Vegan?

Yes. Riboflavin-5'-phosphate is produced industrially by synthesis from certain yeasts, making it plant-derived and suitable for vegan products. It contains no animal-derived components in its commercially produced form. It is widely used in vegan multivitamins and plant-based fortified products.

Is E101(ii) Halal and Kosher?

The compound itself is derived from fermentation or synthesis and contains no animal-derived components, which makes it generally considered halal and kosher in its standard commercially produced form. However, halal and kosher status ultimately depends on the specific production process and certification of the individual supplier. Manufacturers seeking halal or kosher claims on finished products should confirm certification with their ingredient supplier directly.

E101(ii) and Riboflavin Sodium Phosphate: Same Thing

If you are a formulator or buyer researching this ingredient, E101(ii) and riboflavin sodium phosphate are the same compound referenced under different naming systems. The E number is the EU food additive designation. The full chemical name used in pharmacopoeial and technical documents is riboflavin-5'-phosphate sodium, also known as riboflavin sodium phosphate.

For full technical specifications, grades, and supplier information, visit our Riboflavin Sodium Phosphate product page or read our detailed guide on What is Riboflavin Sodium Phosphate: Uses, Grade and Applications.