Sustainable Green Extraction of Thermostable Antioxidants from Banana Flower Waste

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Every year, the global banana industry produces over 44 million tons of waste, including stems, leaves, and flower clusters known as inflorescences. For every ton of bananas harvested, 160 kilograms of these floral structures are discarded.

However, recent research reveals that banana inflorescences are far from useless, they contain valuable bioactive compounds like antioxidants, flavonoids, and phenolic acids, which have significant health benefits.

A groundbreaking 2025 study published in Food and Bioprocess Technology demonstrates how eco-friendly extraction methods can transform this agricultural waste into a source of natural antioxidants, offering sustainable solutions for food, medicine, and environmental conservation.

The Global Challenge of Banana Waste

Bananas are among the most widely consumed fruits globally, with top producers like India (34.5 million tons), China (11.8 million tons), and Brazil (6.85 million tons) contributing to massive annual harvests.

However, banana farming generates staggering amounts of waste. For every ton of fruit produced, farmers discard 100 kilograms of unused bananas, 3 tons of pseudostems , 480 kilograms of leaves, and 160 kilograms of inflorescences.These inflorescences are particularly rich in nutrients.

They contain phenolic compounds, which act as antioxidants to combat oxidative stress linked to diseases like diabetes and cancer. Flavonoids, another key component, are celebrated for their anti-inflammatory and heart-protective properties.

Additionally, banana inflorescences have a protein content of 12.3%, making them a potential ingredient for plant-based foods. Despite this potential, most inflorescences end up in landfills due to the lack of efficient extraction methods.

Eco-Friendly Extraction Methods: A Closer Look

To address this waste, researchers tested three green extraction techniques. Steam distillation, a traditional method using water vapor, yielded only 0.012% extract, proving unsuitable for large-scale use.

Soxhlet extraction, a laboratory technique where solvents are heated and cycled through raw material, was more effective. The team tested four solvents: water, ethanol, 2-methyltetrahydrofuran (2-MeTHF), and hexane.

Water-based extraction (AE) achieved the highest yield (26.4%) and immediate antioxidant activity but lost 57% of its phenolic content after six months.

Ethanol, a renewable alcohol, balanced yield (11.1%) and stability, retaining most antioxidants over time. Meanwhile, 2-MeTHF, a biodegradable solvent from sugarcane, preserved 100% of phenolic compounds during storage. Hexane, effective for fats, failed to extract antioxidants.

Supercritical fluid extraction (SFE), an advanced method using carbon dioxide (CO₂) heated and pressurized to a supercritical state, produced a modest yield (3.9%).

But excelled in extracting flavonoids—32.1 milligrams per gram of extract, the highest ever reported for banana inflorescences. It also prevented thermal degradation, ensuring long-term stability.

Optimizing Extraction: Yield, Antioxidant Power, and Long-Term Stability

The study revealed critical insights into optimizing antioxidant extraction. Water-based extraction (AE) delivered the highest yield (26.4%) and immediate antioxidant potency, with a FRAP (Ferric Reducing Antioxidant Power) value of 61.1 milligrams of Trolox equivalent per gram.

However, its phenolic content halved after six months, making it ideal for short-term applications like natural food preservatives. Ethanol and 2-MeTHF struck a balance between efficiency and stability.

Ethanol yielded 11.1% extract and retained 97% of its phenolic content over six months.

Meanwhile, 2-MeTHF preserved 100% of phenolic compounds and showed the highest Trolox Equivalent Antioxidant Capacity (TEAC), a measure of radical-neutralizing power.

Supercritical CO₂ (SFE) had the lowest yield (3.9%) but outperformed other methods in flavonoid concentration (32.1 milligrams per gram) and stability. Unlike water-based extracts, SFE’s output showed no degradation over six months, making it ideal for pharmaceuticals requiring long shelf lives.

The Science Behind Solvents and Stability

The effectiveness of each method hinges on solvent polarity—a measure of how well a substance dissolves compounds based on their electrical charge. Polar solvents like water and ethanol excel at extracting hydrophilic (water-loving) antioxidants like phenolic acids.

In contrast, nonpolar solvents like hexane target fats but ignore antioxidants. Mid-polarity solvents like 2-MeTHF bridge this gap, preserving both yield and stability.

Temperature and pressure also play vital roles. For example, supercritical CO₂ extraction relies on high pressure (up to 35 MPa) to increase solvent density, boosting yield by 113% compared to low-pressure conditions.

Interestingly, at high pressures, raising the temperature improved yield  a phenomenon called retrograde solubility, where solubility increases with temperature under extreme pressure.

Long-Term Storage: Which Extracts Survive?

After six months of storage at -18°C, water-based extracts (AE) retained only 43% of their phenolic content. In contrast, 2-MeTHF and SFE extracts maintained 100% stability, making them ideal for supplements or medicines.

Ethanol extracts kept 97% of their antioxidants, striking a practical balance for food and cosmetic uses. These results highlight the importance of matching extraction methods to product goals.

For instance, water extraction suits perishable goods, while SFE or 2-MeTHF better serve shelf-stable products.

Industrial Applications: From Food to Fuel

Banana inflorescence extracts could replace synthetic antioxidants like BHT (butylated hydroxytoluene), which are linked to health risks. With a FRAP value of 61.1 mg ET/g, water-based extracts could preserve snacks, oils, and beverages naturally.

Additionally, the inflorescence’s 12.3% protein content offers a sustainable base for plant-based meats.In pharmaceuticals, SFE’s flavonoid-rich extracts (32.1 mg CE/g) hold promise for heart disease and inflammation treatments.

Previous studies show ethanol extracts from banana flowers inhibit harmful bacteria like E. coli and S. aureus, suggesting potential for antimicrobial drugs.With 60% carbohydrate content, banana inflorescences could feed bioethanol production, reducing reliance on fossil fuels. This aligns with circular economy principles, where waste becomes a resource.

Repurposing banana waste reduces landfill use and methane emissions, a potent greenhouse gas. Supercritical CO₂ extraction, which recycles solvents, minimizes chemical pollution compared to hexane. Economically, farmers could profit from selling wast to extraction facilities, while industries gain affordable, natural antioxidants.

Challenges and Future Directions

Despite its promise, scaling these methods faces hurdles. Soxhlet extraction consumes large amounts of water and energy, while SFE requires costly high-pressure equipment.

Future research could explore hybrid techniques, such as ultrasound-assisted SFE, to improve efficiency. Additionally, optimizing solvents for specific climates or cultivars may enhance yields.

Conclusion:

This groundbreaking study transforms banana inflorescences from agricultural waste into a valuable source of antioxidants, offering a sustainable solution for industries worldwide.  Hot water extraction stands out for its high yield, making it ideal for short-term applications like natural food preservatives.

Meanwhile, 2-methyltetrahydrofuran (2-MeTHF) excels in stability, preserving antioxidants over long periods, which is perfect for dietary supplements and medicines. Supercritical CO₂ extraction, though lower in yield, leads in flavonoid concentration and shelf life, making it indispensable for pharmaceuticals requiring long-term stability.