Natural food colourants are gaining ground because of their clean-label appeal. A 2025 review in Foods is direct about the catch: their practical use is often held back by instability under changes in pH, and under heat, light and oxygen.
The useful way to approach a switch is to know which of those stresses each pigment is most sensitive to, and then to ask which of them your product will actually expose it to.
The main pigment groups
The review classifies natural pigments in food into four main types: anthocyanins (red, blue and purple), betalains (red), chlorophylls (green) and carotenoids (yellow, orange and red). It also covers curcumin, from turmeric, and phycocyanin, a blue pigment from cyanobacteria and algae.
| Pigment | Typical sources | Weak points reported |
|---|---|---|
| Anthocyanins | Berries, red cabbage | Water-soluble; colour varies with pH; unstable to pH, temperature and light |
| Betalains | Beetroot, prickly pear | Water-soluble; stable between pH 3 and 7; sensitive to light and heat |
| Carotenoids | Carrots, tomatoes, paprika, algae | Fat-soluble and needs emulsifying for water-based products; sensitive to light and oxidation; stable in acidic conditions |
| Chlorophylls | Green leafy vegetables, algae | Sensitive to pH and heat; colour is lost when the magnesium in the molecule is replaced |
| Curcumin | Turmeric rhizome | Light-sensitive; poor water solubility; strong flavour |
| Phycocyanin | Cyanobacteria, red algae | Sensitive to light, pH and heat; costly to extract |
What each weak point means in a product
pH, and the anthocyanin question
Anthocyanins change colour with pH. The review explains that an acidic environment favours their stable flavylium form, which is why natural acids such as citric, malic and ascorbic acid are widely used to keep the pH low. Anthocyanins suit acidic beverages and confectionery well. In a product closer to neutral, the colour can shift.
Heat: betalains and chlorophylls
Betalains and chlorophylls are both listed as heat-sensitive. For chlorophyll, the review notes that colour is lost when the magnesium in the molecule is replaced, forming pheophytins. A product that is baked, retorted or held hot needs these pigments tested through the full process, not only as a finished sample.
Light and oxygen: carotenoids, curcumin and others
Carotenoids are highly vulnerable to oxidation because of their unsaturated structure, and curcumin is light-sensitive. Here packaging is part of the answer. The review cites work showing that packaging materials with UV-absorbing additives can substantially reduce light transmission in the 200 to 400 nm range, protecting light-sensitive compounds.
Trace metals
Metals can work either way. The review notes that some metal ions, such as aluminium, may improve stability, while copper and iron can catalyse oxidation. Water, equipment and mineral fortificants are all possible sources worth checking.
Ways to improve stability
The review describes both established and newer approaches: co-pigments, antioxidants and metal chelators; micro- and nanoencapsulation using biopolymers; drying technologies and particle size control; and protective packaging. An encapsulated or emulsified form of a pigment can behave very differently from the plain extract, so the form matters as much as the source.
Questions to answer before choosing
- What is the pH of the product, and does it change over shelf life?
- What heat does it see, and for how long?
- Is the pack transparent, and will it sit under shop lighting?
- Is the colour going into a water phase, a fat phase or a dry mix?
- Does the product contain iron, copper or other added minerals?
- What shade must be matched, and how much variation is acceptable?
Permitted colours are set by regulation. Which colours may be used, in which product categories and at what levels differs between markets and is revised over time. Confirm the current rules for your product before finalising a colour system.