The research team, led by Snigdha Homroy and Rajni Chopra at the National Institute of Food Technology Entrepreneurship and Management in Kundli, Haryana, collected discarded Tagetes erecta flowers from a local temple within six to eight hours of generation and processed them within a day to minimise the loss of volatile phytochemicals. The flowers, which had a moisture content of approximately 88 percent, were gently crushed rather than milled to preserve the delicate glandular trichomes that house the oil-bearing volatiles. From this waste stream, the researchers extracted marigold essential oil using four different approaches: conventional hydro-distillation, ultrasound-assisted hydro-distillation, freeze-thaw-assisted hydro-distillation and solvent-free microwave extraction.

The choice of extraction route proved decisive. Hydro-distillation in a Clevenger-type apparatus for four hours yielded 0.0164 grams of oil per 100 grams of fresh flowers. When the flowers were first pre-treated with ultrasound at 500 watts and 20 kilohertz, acoustic cavitation, the violent formation and collapse of microscopic bubbles, tore open cell structures and improved solvent penetration, raising the yield by roughly 25 percent. A freeze-thaw pre-treatment, in which flowers were cycled between minus 80 degrees Celsius and room temperature three times, boosted the yield by about 17 percent, because ice crystals physically rupture cell walls and membranes during freezing, enlarging the porous network available to the extracting water.

Solvent-free microwave extraction, by contrast, performed poorly in this matrix, delivering a yield 85.3 percent lower than conventional hydro-distillation. The authors attribute this to the absence of added water and the limited intrinsic free moisture of the flowers, which restricted internal heating and volatilisation of the essential oil. The result is a useful reminder that green extraction technologies are not universally interchangeable: microwave methods that excel with aromatic herbs, as previous work on rosemary showed, can falter with high-moisture, fibrous floral waste. The relatively low absolute yields across all methods also reflect the use of whole flowers, which mix oil-rich tissues with fibrous, low-oil material, and the reporting of yields on a fresh-weight basis.

Chemical profiling by headspace gas chromatography-mass spectrometry identified 41 phytochemical constituents across the oils, with a profile rich in compounds prized for antioxidant, antimicrobial and anti-inflammatory activity. Nootkatone, limonene, tagetone, piperitone, ocimene, beta-caryophyllene and isoeugenol dominated, although their proportions shifted with the extraction method. Ultrasound-assisted hydro-distillation produced the highest overall content of key volatiles, enriching oxygenated sesquiterpenes and ketones such as nootkatone, which reached 11.15 percent, while freeze-thaw treatment similarly favoured sesquiterpenes. Microwave extraction skewed toward lighter hydrocarbons and phenolics, including isopentane and isoeugenol, which contribute aroma but are less relevant to oxidative protection.

The second half of the study tested whether this waste-derived oil could defend perilla seed oil, a cold-pressed, omega-3-rich oil whose high polyunsaturated fatty acid content makes it exceptionally vulnerable to rancidity. The researchers fortified the oil with marigold essential oil at 500, 1000 and 1500 parts per million and compared the results against 200 parts per million of tert-butylhydroquinone, or TBHQ, the synthetic antioxidant benchmark, and an untreated control. Samples were then subjected to a 20-day Schaal oven test at 60 degrees Celsius, an accelerated storage protocol that compresses months of ambient shelf-life degradation into weeks by speeding the same radical chain reactions that occur in normal storage.

Across every measure, the 1500 ppm marigold treatment performed impressively. Rancimat analysis showed a statistically significant, concentration-dependent extension of the induction period, indicating delayed oxidation onset. Viscosity, which climbs as oxidation generates polymeric degradation products, rose only to 37.1 centipoise in the marigold-fortified oil, compared with 40.3 centipoise in the untreated control. The untreated oil’s peroxide value, a gauge of primary oxidation, soared to 28.63 milliequivalents of oxygen per kilogram by day 20, whereas the marigold-supplemented oil held at 10.03 and TBHQ at 9.71. Acid value, p-anisidine value and conjugated triene content, which track hydrolysis and secondary aldehyde and ketone formation, followed the same pattern, with the highest marigold dose approaching TBHQ performance throughout.

Antioxidant capacity assays reinforced the picture. Untreated perilla oil lost radical-scavenging capacity rapidly, with DPPH inhibition falling from 84.42 to 74.35 percent and ABTS inhibition from 80.15 to 66.40 percent over the storage period. The 1500 ppm marigold sample, by contrast, retained 83.86 percent DPPH and 72.94 percent ABTS inhibition after 20 days, losses of less than seven percent, comparable to TBHQ-treated oil. The oil also preserved its golden carotenoid pigments better, retaining a yellow Lovibond value of 12.2 against 9.1 for the control. Hierarchical cluster analysis of all stability parameters grouped the control and 500 ppm samples together as low-stability outliers while placing the 1500 ppm marigold oil in the same high-stability cluster as TBHQ, a statistical confirmation that the floral waste extract can match a regulated synthetic preservative at its maximum permitted concentration.

The protective mechanism stems from the oil’s constellation of bioactive volatiles, which scavenge free radicals, chelate pro-oxidant metals and interrupt lipid peroxidation chain reactions, with synergy among compounds such as beta-caryophyllene, nootkatone and isoeugenol likely amplifying the effect. The study’s significance extends beyond food chemistry. It couples two sustainability goals at once: diverting a vast, culturally generated waste stream from landfill and offering food manufacturers a clean-label alternative to synthetic antioxidants such as BHA, BHT and TBHQ, whose potential carcinogenic, genotoxic and endocrine-disrupting effects have drawn increasing scrutiny in animal and mechanistic studies. The authors note that future work should clarify the underlying preservation mechanisms and extend testing to other oxidation-sensitive oils such as flaxseed and chia. If those trials succeed, the garlands left behind at temples across India could become a genuine industrial resource, turning ritual offerings into shelf life for the world’s healthiest cooking oils.

Subject of Research: Extraction of essential oil from marigold floral waste and its use as a natural antioxidant to stabilise polyunsaturated fatty acid-rich perilla seed oil.

Article Title: Valorisation of marigold floral waste for essential oil extraction and its application in stabilisation of PUFA rich perilla seed oil

Article References: Homroy, S., Madan, H., Sharma, S., Chopra, R., & Kumari, R. (2026). Valorisation of marigold floral waste for essential oil extraction and its application in stabilisation of PUFA rich perilla seed oil. Discover Green Chemistry, 1(1), Article 16. https://doi.org/10.1007/s44509-026-00015-1

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00015-1

Keywords: marigold floral waste, Tagetes erecta, essential oil, hydro-distillation, ultrasound-assisted extraction, solvent-free microwave extraction, perilla seed oil, natural antioxidants, oxidative stability, TBHQ, omega-3, waste valorisation