The natural blue colouring problem
Blue is one of the hardest colours to achieve from natural sources in food. The dominant synthetic blue dye — FD&C Blue No. 1 (Brilliant Blue FCF, E133) — has raised concerns in some consumer markets. Natural alternatives are rare:
- Butterfly pea flower (Clitoria ternatea) — pH-sensitive, shifts from blue to purple in acidic conditions
- Gardenia (genipin-derived blue) — complex production, limited regulatory approval
- Phycocyanin from spirulina — the most commercially developed and widely regulated natural blue
Phycocyanin’s vivid turquoise-blue colour, combined with spirulina’s “natural superfood” positioning, has made it increasingly attractive to food manufacturers seeking clean-label blue colouring.
EU regulatory status: E3 spirulina extract
In the European Union, spirulina extract (standardised for phycocyanin content) is approved as a natural food colouring under Regulation (EC) No 1333/2008 as “spirulina extract” or E3 (as part of the “natural colours” category in some member state implementations).
The approval specifies that the extract may be used in specific food categories including confectionery, non-alcoholic beverages, desserts, and decorations. Maximum use levels are set per food category.
In the United States, phycocyanin from spirulina has a more complex regulatory path — not approved as a colour additive by the FDA, though spirulina extract containing phycocyanin may be used as an ingredient (not declared as a colouring) in some products. This distinction has commercial implications for US food manufacturers.
How phycocyanin colouring is produced
Commercial phycocyanin for food use is produced through:
- Aqueous extraction: spirulina biomass is mixed with water, which extracts the water-soluble phycocyanin protein
- Filtration: cell debris is removed, leaving a deep blue solution
- Purification: depending on the purity grade required, various chromatography and precipitation steps follow
- Concentration and drying: spray-dried at low temperature to produce a powder (at higher temperatures, phycocyanin decomposes — defeating the purpose)
Purity is expressed as the ratio A620/A280 — the absorbance at 620 nm (phycocyanin) divided by total protein absorbance at 280 nm. Food-grade phycocyanin is typically 0.5–1.5; pharmaceutical/ research-grade reaches 4.0+.
Stability limitations
The fundamental limitation of phycocyanin as a food colouring is its instability:
- Heat: Phycocyanin degrades rapidly above 60°C. It cannot survive pasteurisation, baking, or cooking. This restricts applications to cold-processed, chilled, or ambient-temperature products.
- Light: UV and visible light cause bleaching over days to weeks. Products using phycocyanin require opaque packaging or short shelf lives.
- pH: Phycocyanin is stable at pH 5–7 but degrades at pH below 4 (common in acidic beverages). It shifts from blue-green to colourless in low-pH environments, limiting use in juices and carbonated drinks.
- Oxidation: Exposure to air accelerates degradation. Products must be formulated with antioxidants or minimal headspace.
These limitations explain why phycocyanin colouring is most commonly found in frozen products (ice cream, frozen desserts), chilled products (yoghurt coatings, chilled confectionery), and candy coatings rather than shelf-stable beverages or baked goods.
Commercial applications
- Confectionery: Blue hard candy shells, cake decorations, marshmallows — the most stable application category for phycocyanin
- Ice cream and frozen desserts: Stability in frozen conditions is good; the colour performs well in dairy and non-dairy ice cream bases
- Sports drinks and cold beverages: Limited to products with near-neutral pH and short shelf lives; more common in refrigerated formats
- Powder mixes: Dry spirulina/phycocyanin powder incorporated into powdered beverages, supplement mixes, and smoothie bowls — shelf-stable in powder form, colour activates on addition of cold liquid
The “blue spirulina” supplement market
The growth of food-grade phycocyanin has driven the “blue spirulina” supplement market — isolated phycocyanin powder sold at significantly higher prices than whole spirulina, primarily for social media-friendly blue smoothie bowl applications.
From a nutritional standpoint, this is a poor trade-off: the protein, iron, minerals, beta-carotene, and full phycocyanin complex of whole spirulina are absent in isolated phycocyanin extract. See the case against blue spirulina for the full analysis.
Implications for whole spirulina consumers
The food colouring applications do not directly affect supplement consumers, but they have two indirect implications:
- Growing phycocyanin demand from the food industry has incentivised producers to develop better quality processing methods that preserve phycocyanin — which benefits supplement quality overall
- The same heat-stability limitations that restrict food colouring use apply to home cooking: spirulina added to hot dishes loses its blue-green hue and phycocyanin bioactivity (though protein and minerals remain) — consistent with the advice to add spirulina to cooled dishes