In a world striving for sustainability, the vibrant pigments of plants and microbes are becoming powerful allies, revolutionizing how we think about color, health, and environmental responsibility.
Imagine a world where the brilliant orange of a sunset, the vibrant red of a tomato, and the deep yellow of a marigold can be harnessed not just for their beauty, but for their power to promote health and protect our planet. This is the world of carotenoids.
These natural pigments, found in fruits, vegetables, and even some bacteria, are more than just nature's paintbrush; they are potent antioxidants with anti-inflammatory and even anticancer properties.
For decades, extracting these valuable compounds relied on methods that were inefficient and harmful to the environment. Today, a revolution is underway. Scientists are pioneering "green extraction" technologies—innovative, eco-friendly methods that efficiently recover these pigments while aligning with the principles of sustainability and a circular economy.
Carotenoids are a class of over 700 natural pigments synthesized by plants, algae, and some bacteria and fungi 8 . They are responsible for the stunning colors we see in carrots, pumpkins, salmon, and flamingos. Chemically, they are tetraterpenoids, which means their structure is built from eight isoprene units, forming a long polyene chain 5 .
This chain is the secret to their function; it allows them to absorb light and act as powerful antioxidants by neutralizing harmful free radicals in the body 5 8 .
Natural colorants, eyesight protection, immunity boost
Provides color to farmed salmon and shrimp
Antioxidant and UV-protection properties
Used as natural colorants and for their health benefits, such as protecting eyesight and boosting immunity 5 . Beta-carotene, for instance, is a crucial precursor to vitamin A 5 .
Astaxanthin is added to feed to provide the characteristic pink color in farmed salmon and shrimp 8 .
Leveraging their antioxidant and UV-protection properties for skincare products .
Traditional methods for extracting carotenoids often involve large volumes of hazardous organic solvents like hexane and petroleum ether, which pose risks to both human health and the environment 4 . Furthermore, these methods can be inefficient, with long processing times that risk degrading the heat- and light-sensitive carotenoids 5 .
Green extraction technologies address these challenges head-on. They aim to reduce energy consumption, use non-toxic alternative solvents, and ensure the safety and quality of the final extract 3 . The core principle is to align with green chemistry, minimizing environmental impact while maximizing efficiency.
| Aspect | Traditional Methods (e.g., Solvent Maceration) | Modern Green Methods (e.g., SFE, UAE) |
|---|---|---|
| Solvents | Often hazardous organic solvents (e.g., hexane) 4 | Green solvents (e.g., supercritical CO₂, vegetable oils, SUPRAS) 3 4 7 |
| Energy Consumption | High (e.g., prolonged heating in Soxhlet) 4 | Generally lower and more efficient 3 |
| Processing Time | Long extraction times (hours) 4 | Significantly faster (minutes) 3 |
| Environmental Impact | High, due to solvent toxicity and waste 4 | Greatly reduced, with better sustainability profiles 7 |
| Carotenoid Degradation | Higher risk due to heat and long exposure 5 | Lower risk, as many methods operate at mild temperatures 3 4 |
SFE, particularly using supercritical CO₂, is a flagship green technology. CO₂ is made to behave like both a gas and a liquid by heating and pressurizing it beyond its critical point (31.1°C and 73.8 bar) 4 .
It is non-toxic, non-flammable, and easily removed from the final extract, leaving no harmful residues 1 4 . SFE is excellent for extracting non-polar carotenes like lycopene and β-carotene.
UAE uses high-frequency sound waves to create cavitation bubbles in a liquid solvent. When these bubbles collapse near plant cells, they generate intense shockwaves that disrupt cell walls 3 4 .
This method drastically reduces extraction time and solvent consumption and can be performed at lower temperatures, preserving the sensitive compounds.
A compelling 2025 study perfectly illustrates the power and potential of green extraction 7 . Researchers tackled the problem of citrus peel waste—which makes up 55-70% of the fruit's weight—by comparing two green methods for recovering carotenoids from citron, orange, and tangerine peels.
The same peel material was mixed with a solvent made from water, ethanol, and octanoic acid, which self-assembles into nanostructures that efficiently capture carotenoids 7 .
The carotenoid-rich extracts from both methods were then encapsulated using chickpea protein isolate via freeze-drying to protect them from degradation.
| Citrus Peel | Extraction Method | Total Carotenoid Content | Antioxidant Activity |
|---|---|---|---|
| Orange | CPE | Highest Yield | Strongest Activity |
| SUPRAS | Moderate Yield | Moderate Activity | |
| Tangerine | CPE | High Yield | High Activity |
| SUPRAS | Moderate Yield | Moderate Activity | |
| Citron | CPE | High Yield | High Activity |
| SUPRAS | Moderate Yield | Moderate Activity |
CPE consistently outperformed SUPRAS in both carotenoid yield and antioxidant activity across all citrus types. Orange peel was identified as the most potent source.
The encapsulation process was highly successful, with efficiencies between 82.4% and 89.0%, meaning the protective protein coat effectively trapped the carotenoids.
When evaluated with the EcoScale tool, CPE scored an excellent 92 points, while SUPRAS also achieved a satisfactory 70 points 7 .
Working with sensitive compounds like carotenoids requires specific tools and reagents to ensure accurate and reproducible results.
| Reagent / Material | Function and Importance in Research |
|---|---|
| Butylated Hydroxytoluene (BHT) | An antioxidant added to extraction solvents to prevent the oxidation and degradation of carotenoids during the extraction process 6 9 . |
| Acetone, Methanol, Petroleum Ether | Common solvent systems used in different combinations to efficiently dissolve and separate carotenoids based on their polarity 2 6 9 . |
| Magnesium Carbonate | Added during tissue homogenization to neutralize plant acids that can otherwise degrade carotenoids 9 . |
| C30 Chromatography Column | A specialized type of column used in High-Performance Liquid Chromatography (HPLC) that provides superior separation of the various carotenoid isomers compared to standard C18 columns 6 . |
| Tetrahydrofuran (THF) | An effective solvent for disrupting plant tissues and extracting a wide range of carotenoids, including the non-polar lycopene 9 . |
| Trans-β-apo-8'-carotenal | A compound frequently used as an internal standard during HPLC analysis to quantitatively measure the recovery and concentration of target carotenoids 6 . |
The shift to green extraction methods is more than a technical improvement; it is a fundamental step towards a more sustainable and circular economy. By transforming agricultural waste, like citrus peels, into high-value, health-promoting products, we reduce waste and create new value chains 7 . The use of food-grade, GRAS (Generally Recognized As Safe) solvents means the resulting extracts can be directly incorporated into functional foods, nutraceuticals, and cosmetics, simplifying production and enhancing consumer safety 7 .
As research continues, the synergy between green extraction and synthetic biology promises an even brighter future. Scientists are engineering microorganisms to produce carotenoids efficiently through fermentation, offering a controlled and scalable source that is independent of climate and season 8 . When combined with clean, efficient extraction technologies, this paves the way for a new era of natural pigment production.
The journey of a carotenoid, from a molecule hidden within a piece of fruit waste to a potent ingredient safeguarding our health, exemplifies how scientific innovation can harmonize human well-being with planetary sustainability. The future, it seems, will be colored in nature's most vibrant and sustainable hues.