Due to fast growth of clean label movement, the term natural colour was defined by “Regulation (EC) No 1333/2008” which explains the detailed rules on the use of food additives. This regulation was updated in 2010 (Commission Regulation 257/2010) and established a program for re-evaluation of approved natural colours. Natural colorants are preparations obtained from a wide range of sources like vegetables, fruits, plants, minerals and other edible natural sources by physical and/or chemical extraction resulting in a selective extraction of the pigments relative to the nutritive or aromatic constituents. The natural colorants can be divided into dyes (colour that is soluble in a medium) and pigments (finely ground particles of colour which are suspended in a medium).

BonuPrint® (BP) is a fine, homogenous, liquid pigment dispersion for solid oral dosage form which provides possibilities to print logos, brand names or barcodes onto oral dosage forms. Natural pigments can play an important role to increase the availability of the BP in different nutraceutical fields. Therefore, development of a BP with clean label approved natural pigments which provides similar characteristic like the standard BP can increase the range of its applications.

Printing inks such as BP are composed of liquid phase and solid phase. The liquid phase is used as a vehicle system to carry solid contents, adjust viscosity and drying time of the ink, whereas the solid phase is a polymer responsible for film formation, a covering agent to provide enough opacity and colour pigments to produce different colours. Depending on the used liquid phase, they can be divided into water based and solvent based inks. Generally, the water based inks are a mixture of mainly water and a small amount of alcohol as vehicle system, whereas the solvent based inks are a mixture of alcohols as vehicle system. The two types of inks have similar applications but the main difference is the easier handling and cleaning process of water based inks.

Download the full scientific study (poster) here:
BIOGRUND_BonuPrint®, a natural printing ink for the food and nutraceutical industries

Two examples of natural dyes and ingredients that are also vitamins:

Riboflavin (lactoflavin, vitamin G) is a natural dye and vitamin B2.

Beta-carotene is an active ingredient from the group of carotenoids and a natural colouring and ingredient of many fruits and vegetables, such as spinach, almonds and carrots. It can be converted into vitamin A (Axerophtol, Retino) in the intestine.

Vitamins – Definition: Vitamins, so-called organic compounds, are not needed by the human body as energy sources, but for vital functions that cannot be sufficiently synthesized by the metabolism. Vitamins are taken up with food by the human body.

Natural dyes – Definition: The natural dyes are of vegetable or animal origin. Plant examples are: Chlorophyll, indigo, blue wood, saffron, curcuma, alizarin and madder. Animal examples are: Cochineal, purple and haemoglobin, the red blood pigment.



Synthetic dyes are industrially produced artificial dyes. Most of them have been newly developed by industry. However, various natural dyes are now also produced on an industrial scale for cost reasons. From a chemical point of view, synthetic dyes can basically be divided into 3 groups: Azo dyes, triphenylmethane dyes and anthraquinone dyes.

  1. azo dyes:

In numerical terms, azo dyes are the largest dye class of synthetic dyes. They can be characterized by the general formula R1-N=N-R2. An azo group is particularly typical for azo dyes. This is -N=N- and has chromophoric nitrogen double bonds.

Amines and in the simplest case aniline are used as starting materials. The variety of the azo dyes is justified by the simple substitution of the hydrogen atoms on benzene rings, which then influence the azo bond auxochrom and allow an exact adjustment of the colour nuances.

The representatives of these dyes are often lightfast, colour stable and can have particularly strong colours.

  1. triphenylmethane dyes:

The second group consists of triphenylmethane dyes. They have a triphenylmethane basic body and their phenyl rings carry at least one activated substituent in the para- or ortho-position, such as the amino groups. A well-known example would be here: Critical violet or phenolphthalein.

Phenolphthalein in the colorless leukoform is coloured deep pink by deprotonation. They are very popular in food colouring and cosmetics.

  1. anthraquinone dyes:

Almost any colour can be produced using hydroxy and amino groups as substituents. There are two ways to synthesize anthraquinone. The first is oxidation or the second is electrophilic substitution using a catalyst.

Indanthrene blue is a particularly wash and light-resistant anthraquinone dye. The name Idanthren can also be derived from this, which is used today as a trademark for particularly high-quality dyes.


As the name suggests, natural dyes can be extracted from nature (e.g. from animals or plants). Plant dyes include chlorophyll and saffron. Animal origin are, for example, cochineal and purple, as well as haemoglobin, the red blood pigment.

Colouring foods are natural raw materials that are used as colouring agents due to their colouring properties. The colouring foods include beetroot, spinach, hibiscus, curcuma, tomatoes, grapes, peppers, carrots, etc.

Colouring foods are considered as ingredients with colouring properties and not as colouring agents. Therefore, they are not subject to any quantitative limit. They are used, for example, in ice cream, confectionery, fruit preparations and dairy products.



In the EU, iron oxides are currently the subject of discussion. France and Belgium, for example, are discussing whether the use of iron oxides should be avoided because they contain nanoparticles. Nanoparticles are classified as dangerous here. There is a suspicion that individual particles settle in the human body and cannot degrade.

However, very little is known about the effects of nanoparticles on humans and the environment. It is unclear whether they can be absorbed by humans via the skin and respiratory tract if such nanoparticles are released uncontrollably. For reasons of uncertainty, several countries are already banning the use of iron oxides, while other countries are allowing them even in food products without hesitation.


For pigments and dyes there are different upper dosage limits. These even differ within the EU, the USA and other countries. Regulatories are therefore not harmonized, but differ from pigment to pigment and from country to country. France and Belgium, for example, often have different regulations to the rest of the EU.

The EU has set corresponding colour limits for synthetic dyes (e.g. Yellow 6, Blue 2 = Indigo Carmin). Dyes can be coated with aluminium hydroxide to form pigments. There are often different limit values for aluminium than for the pigment used. The resulting pigment again has different limits.