Have you ever wondered why strawberry-flavored candy is always red, but once you bite into it, that red sometimes fades, darkens, or turns into an indescribable grayish pink?
The answer is: that red comes from certain "pigment molecules" – a group of diva-like performers who are afraid of light, heat, acid, and oxygen. Change the environment even slightly, and they go on strike.
But in recent years, a group of scientists has been asking a very rebellious question: Can we give food color without using any pigment at all?
The answer is yes. And the method is based on the same principle that gives butterfly wings and peacock feathers their brilliant hues.
Part I: Two Ways to Create Color – One Is Chemistry, the Other Is Physics
Molecular Pigments: Like Dyeing Fabric, But for Food
The various "natural pigments" we eat – anthocyanins from purple cabbage, beta-carotene from carrots, betanin from beets – all work on a simple principle: these molecules absorb some wavelengths of light and reflect others.
Think of a beta-carotene molecule as a "blue light vacuum cleaner." It sucks up the blue part of white light and reflects the remaining red and yellow light back to your eyes. That's why you see orange.
This approach is straightforward – just add it to the food and you're done. But the downside is: these "vacuum cleaners" are fragile.
- Exposed to acid, anthocyanins shift from red to purple to blue;
- Exposed to high heat, betanin breaks down into colorless compounds;
- Exposed to sunlight, many natural pigments slowly fade;
- Exposed to metal ions (like cooking in an iron pot), colors can turn dull and muddy.
That's why your strawberry candy, left sitting in the sun for too long, gradually loses its appeal.
Structural Color: Like Butterfly Wings That "Trick" Your Eyes
Now let's talk about the method that sounds a bit like science fiction.
Some things have no color of their own, yet they display vibrant hues – butterfly wings, peacock feathers, soap bubbles, the rainbow sheen of a CD.
The secret lies in their surfaces, which contain incredibly tiny structures – so small they're a thousand times thinner than a human hair. These microscopic structures are arranged in orderly patterns, acting like tiny mirrors that only reflect specific wavelengths of light.
This is physical structural color. It needs no pigment molecules at all. It's pure physics – manipulating light through structure alone.
Imagine stacking ping-pong balls into a neat cube and shining a flashlight on it. You'll notice certain angles look much brighter than others. That's structural color in its simplest form.
Scientists have now brought this principle into the food world. They use plant polysaccharides (the edible stuff in plants – cellulose, starch, etc.) to self-assemble into these microscopic structures in water, then fix those structures onto the surface of candy. The result: colorful candy without adding a single pigment molecule.
And here's the magical part: this color isn't afraid of light, heat, acid, or oxidation. Because it doesn't come from a fragile molecule – it comes from a physical structure. As long as the structure stays intact, the color stays put.
Part II: Two Completely Different Personalities
If molecular pigments are the "all-rounder," then structural color is the "gifted specialist."
Molecular Pigments: Can Do Everything, But Gets Tired Easily
Molecular pigments can be used in almost any food:
- Add a drop to a drink, and it instantly looks like fruit juice;
- Stir it into yogurt, and it turns a lovely strawberry pink;
- Knead it into bread dough, and it holds its color after baking;
- Mix it into sausage, and it gives that appetizing reddish tint.
From liquids to solids, from acidic to alkaline, from cold dishes to hot meals – molecular pigments can handle it all. They just perform better in some environments than others – like someone who can do any job, but whose performance varies depending on where they are.
Plus, molecular pigments have a hidden bonus: they can double as nutrients. Beta-carotene converts into vitamin A in your body. Lycopene is an antioxidant. When you eat them, you're not just getting color – you're getting health benefits too.
Structural Color: Unbeatable in Specific Scenarios, But Very Limited
Structural color isn't nearly as versatile. It has several "fatal flaws":
First, it hates water. Those carefully assembled microscopic structures collapse when exposed to lots of moisture, like a Lego tower hit by a wave. So you can't put it in drinks, yogurt, or sauces – the color vanishes instantly.
Second, it hates oil. Grease seeps into the gaps between structures, changing how light reflects, and the color goes haywire.
Third, it hates being manhandled. Stirring, squeezing, chewing – all these mechanical actions destroy the microstructures. So it can't go into bread dough or sausage filling.
Fourth, it has a narrow temperature window. Too hot, and the structure melts away like ice.
So where can it actually be used? Answer: candy shells, decorative sugar sheets, edible films on chocolate, freeze-dried fruit coatings.
These scenarios share common traits: low moisture, low temperature, minimal handling, thin layers. They're exactly where structural color shines brightest.
And in these scenarios, structural color can do something molecular pigments never can: it changes color depending on the viewing angle. Like the rainbow sheen on a CD – gold from one side, green from another. This "iridescent effect" is a killer selling point for premium desserts and chocolates.
Part III: Which One Is More "Natural"? It's Trickier Than It Looks
You might think: structural color uses plant polysaccharides and adds no pigment at all – surely it's more "natural" than molecular pigments, right?
It's not that simple.
The "Natural" Dilemma of Molecular Pigments
Molecular pigments come in two types: synthetic (like Yellow 5, Red 40) and natural (like anthocyanins, beta-carotene).
Synthetic ones are a non-starter – consumers hear "petroleum-derived" and immediately say no. Natural ones sound better, but they have their own problems:
- To extract these pigments, factories use organic solvents (hexane, acetone, ethanol). Trace residues are a concern;
- The definition of "natural" varies by country. Beta-carotene made by yeast fermentation is considered natural in the US, but requires a lengthy novel food approval in Europe;
- Most importantly, no matter how natural the source, seeing "color added" on the ingredient list already puts consumers on guard.
The "Natural" Trap of Structural Color
Structural color's ingredients are indeed clean – just cellulose, starch, pectin – things already present in food. The ingredient list won't say "Red 40" or "Yellow 5"; it'll say "cellulose" or "modified starch." Consumers read that and think: "Oh, that's just what flour is made of. No problem."
But here's the catch most people miss: structural color uses nanoparticles.
Cellulose nanocrystals (CNC) are only tens to hundreds of nanometers wide – barely larger than a virus. When you eat particles this small, can they cross your intestinal wall into your bloodstream? Can they accumulate in organs? We don't yet have definitive answers.
The European Union already requires additional safety data for nanomaterial-based food additives. China's food safety standards haven't specifically addressed nanomaterials yet, but it's only a matter of time.
So structural color's "natural" label is currently a temporarily valid pass – in the long run, more scientific evidence will be needed to back it up.
Part IV: Cost – Who Wins on Price?
On this front, molecular pigments are way ahead.
After decades of industrial optimization, production costs for molecular pigments are very low. Especially in recent years, as yeast fermentation technology for carotenoids has matured, costs have dropped dramatically:
- Extracting lycopene from tomatoes used to cost over $1,000 per kilogram;
- Now, fermenting it with yeast costs just $100–200 per kilogram;
- Some companies are even using CO₂ captured from steel mills as feedstock, driving costs even lower.
By contrast, structural color is still stuck at "lab scale" pricing:
- Turning cellulose into nanocrystals requires strong acid treatment, repeated washing, and dialysis purification – driving costs to 5–10 times that of molecular pigments;
- The self-assembly process is extremely sensitive to temperature, concentration, and ionic strength – yield rates are low;
- The hardest step is drying – how do you remove water without destroying the microstructure? Air drying causes deformation, freeze drying cracks it, spray drying destroys it entirely. This remains a major engineering challenge.
So today, structural color works, but it's expensive. It's commercially viable only in high-end chocolates, premium candies, and other scenarios where customers pay a premium for visual appeal.
Part V: Regulation – One Has a Clear Path, the Other Is Making Its Own
Molecular pigments have well-established regulatory pathways in every major market:
The US FDA maintains a clear list of permitted color additives, specifying which can be used, in what amounts, and in which foods;
- The EU has a unified additive numbering system (E-numbers), with E100 through E180 covering colors;
- China's GB 2760 standard lists approximately 70 permitted colorants.
If you want to launch a new molecular pigment (say, a novel red pigment produced by a newly discovered yeast strain), you simply submit safety data following each country's requirements. The process takes time and money, but the path is clear.
Structural color faces an awkward situation: no food safety regulation anywhere in the world has a category called "structural color."
Just imagine trying to explain it to regulators:
"I'd like to add a substance to candy that has no color itself, but creates color when applied to the surface."
Regulator asks: "What is this substance?"
"It's cellulose."
"We know cellulose – that's a thickener, not a color additive."
"But it does make the candy change color..."
"How do you prove the color comes from this 'structure' you describe, rather than from impurities or contamination?"
"Uh..."
That's the regulatory dilemma facing structural color today. It's not that it can't be approved – it's that nobody knows which pathway to use. File it as a color additive? A thickener? A novel food ingredient? Each option has problems.
Colorolicious, the UK startup behind this technology, is taking an unconventional approach: no patent filings, no regulatory submissions yet. Instead, they're signing NDAs and doing collaborative R&D with food companies. Essentially, they're betting – betting they can get the technology and market running before the regulatory framework catches up.
Part VI: So, Who Wins?
That's the wrong question. They're not rivals – they're teammates.
Think of molecular pigments as your everyday chef – can cook anything, delivers reliably every day, affordable prices, dependable flavors. Think of structural color as a Michelin-star dessert artist – only makes one dish, but that dish is breathtaking and impossible to replicate.
The smartest approach is: let them collaborate.
Picture this: a premium chocolate with a shell that shimmers using structural color – gold, green, blue flashing as you turn it in your hand, begging to be photographed and shared. Then you bite into it, and the filling inside is colored with betanin or beta-carotene – a uniform, rich red that looks beautiful when you break the chocolate in half.
This is the "hybrid architecture": physics on the outside, chemistry on the inside. Each plays to its strengths. Perfect teamwork.
Part VII: What's Next? When Will We Eat It?
Based on current technology progress and industrialization timelines, here's a rough roadmap:
2026–2027: First structural-color candies hit the European market (likely a niche product from a startup);
2027–2028: The US FDA provides preliminary guidance on how to classify structural color products;
2028–2029: China's GB 2760 may indirectly cover structural color through revisions or expanded interpretations;
2029–2030: Production costs for structural color drop to 2–3 times that of molecular pigments, enabling adoption in premium candy and bakery decoration;
Post-2030: Structural color expands into edible packaging films, functional coatings, and adjacent fields – but never replaces molecular pigments as the mainstream solution.
One last thought,
Physical structural color isn't here to "kill" molecular pigments. It's here to fill the gaps – places where molecular pigments struggle (like candy shells that fade in sunlight), structural color steps in perfectly. For the vast majority of food applications, molecular pigments remain the reliable old friend.
The best food coloring strategy for the future isn't picking one over the other. It's using both hands.
