The starting materials were far from glamorous. Grape seed oil is a secondary product of winemaking, extracted from the pomace left behind after pressing. A large share of olive oils, meanwhile, never make the grade for extra virgin classification; roughly 41 percent of collected oils in some seasons are downgraded because of defects or excessive acidity, then refined and blended into cheaper commercial products. Refining stabilizes these oils, but it strips out most of the aromatic and bioactive compounds that give premium oils their complexity, leaving behind a neutral-tasting lipid with little antioxidant punch. Aromatization offers a route to upgrade these bland carriers, and pairing the process with food by-products multiplies the sustainability payoff.

The Italian team turned to ultrasound-assisted extraction, a green technology that accelerates the transfer of lipophilic compounds from plant material into oil. A 38 kHz probe-type system operating at 70 percent of a 1000 W generator delivered cavitation bubbles that collapse violently in the oil, rupturing plant cell walls and driving phenolics, capsaicinoids, and pigments into the surrounding fat in minutes rather than days. Dried chili peppers and basil leaves, both rejected from normal sale channels for failing size or shape standards, were ground and processed at carefully controlled low temperatures of 30 to 35 degrees Celsius for just 10 minutes each. Conventional infusion methods can take days at room temperature, exposing the oil to oxidation throughout; the ultrasound route compresses that window dramatically.

Chemically, the transformation was striking. Basil flavoring pushed total phenolic content more than 30 percent higher than chili flavoring, with basil-infused olive oil reaching levels comparable to unflavored extra virgin olive oil. Chili pepper, by contrast, was the star of carotenoid enrichment: both chili-flavored oils showed significant carotenoid uptake, while the controls and basil versions showed little or none. These pigments are largely lost during refining, which can strip as much as 98.6 percent of carotenoids from an oil, so their recovery via ultrasound represents a meaningful restoration of both color and nutritional value. Radical-scavenging activity measured by the DPPH assay rose significantly in all flavored oils except chili-flavored olive oil, suggesting that non-polyphenolic antioxidants such as tocopherols and capsaicinoids also migrated into the oils.

Quality parameters told a more nuanced story. Peroxide values and free fatty acid levels remained essentially unchanged after chili flavoring, but basil flavoring raised peroxide values considerably, from around 3 to over 13 meq O2/kg in olive oil and above the Codex reference threshold of 10 for refined seed oils in grape seed oil. The researchers attribute this difference to the flavoring matrix rather than the oil itself, pointing to the varying endogenous enzymes and pro-oxidant compounds that different herbs carry. Still, the dramatically shortened processing time offers an advantage over traditional infusion, which in one published comparison caused a sevenfold rise in free fatty acids and a doubling of peroxide values over six days. The takeaway is that processing conditions and storage need to be tailored to each specific herb and oil combination.

Chemistry, however, is only half the battle. A functional oil nobody wants to buy is a commercial failure, so the team recruited 70 untrained consumers for a rigorous sensory trial at the University of Camerino under controlled ISO-standard conditions. In a first blind phase, participants rated appearance, odor, flavor, and pungency on hedonic scales without knowing anything about the samples. Chili-flavored oils came out on top, earning overall liking scores of 6.23 and 6.14 for olive and grape seed versions respectively, while basil versions scored 5.49 and 4.86. Interestingly, the unfamiliarity of grape seed oil did not drag its scores down relative to olive oil, suggesting that intrinsic sensory performance can compensate for limited consumer knowledge when no other cues are available.

Just-About-Right scales and penalty analysis pinpointed exactly where each formulation fell short. For both chili-flavored oils, pungency and flavor were frequently rated as too intense, with more than 60 percent of consumers finding the spiciness of chili-flavored grape seed oil excessive, making it the main driver of lost liking. Basil oils suffered the opposite problem: over half of participants rated their aroma and flavor as too weak, indicating a need for higher herb loading or longer extraction. These findings give product developers a concrete reformulation roadmap: tame the capsaicin burn, amplify the basil bouquet, and the oils themselves matter less than the flavoring matrix.

The most psychologically intriguing results came in the second phase, an informed expectation test in which participants learned the oil type, the flavoring matrix, and the polyphenol and antioxidant content of each basil oil before re-rating them. Flavor liking jumped by 15.37 percent for basil olive oil and 20.37 percent for basil grape seed oil compared to blind scores, a statistically significant assimilation effect consistent with expectation-disconfirmation theory. Overall liking rose 11.66 and 13.79 percent respectively, though those gains did not reach statistical significance. The effect was strongest for grape seed oil, the less familiar product, supporting the idea that positive sustainability and health information fills the knowledge gap that unfamiliar products typically suffer from.

Purchase intention shifted even more dramatically. Willingness to repurchase climbed from 46 to 64 percent for basil-flavored olive oil and from 29 to 46 percent for basil-flavored grape seed oil once the enrichment story was disclosed. Under expectation-disconfirmation theory, the positive cues about bioactive content and by-product valorization generated expectations that consumers then integrated into their hedonic judgments, even though the oils themselves were identical between the blind and informed rounds. The researchers note this pattern aligns with earlier work showing that nutritional and health-related claims can reshape sensory perception, and they caution that their same-session design, though mitigated by randomization and palate cleansing, may have introduced memory effects.

The study has limitations that the authors openly acknowledge: spectrophotometric assays captured overall antioxidant enrichment but not individual compounds, storage stability and batch variability remain untested, and the panel was overwhelmingly Italian, which matters given the cultural variability of spice tolerance. Future work should add chromatographic profiling, complementary antioxidant assays, shelf-life studies, and broader consumer panels. Still, the core message stands: a 10-minute burst of ultrasound can convert two discounted oils and two categories of agricultural waste into antioxidant-rich flavored products that consumers actively want, provided the label tells them why it matters. For an industry under pressure to cut waste and add value, the sound of sustainability may well be a 38 kHz hum.

Subject of Research: Ultrasound-assisted enrichment of refined olive and grape seed oils with basil and chili pepper by-products and its effect on consumer perception

Article Title: From By‐Products to Flavored Oils: Ultrasound‐Assisted Enrichment of Refined Olive and Grape Seed Oils and Consumer Perception Under Blind and Informed Conditions

Article References: Corsetti, S., Bailetti, L. I., Calzolari, S., Floridi, M., Sagratini, G., & Alessandroni, L. (2026). From By‐Products to Flavored Oils: Ultrasound‐Assisted Enrichment of Refined Olive and Grape Seed Oils and Consumer Perception Under Blind and Informed Conditions. Food Science & Nutrition, 14(9), Article e72374. https://doi.org/10.1002/fsn3.72374

Image Credits: AI Generated

DOI: 10.1002/fsn3.72374

Keywords: ultrasound-assisted extraction, grape seed oil, olive oil, food by-products, basil, chili pepper, antioxidants, polyphenols, carotenoids, consumer perception, circular economy, sensory evaluation

The research, led by Ibrahim Selvikaya and Abdurrahim Yilmaz at Bolu Abant Izzet Baysal University in Türkiye, together with colleagues at Atatürk University, Kocaeli University, Igdir University, and Recep Tayyip Erdogan University, set out to test whether foliar nano-micronutrition could fortify basil (Ocimum basilicum L.) against water deficit. The team chose a greenhouse factorial design that crossed two irrigation regimes—full watering at 100 percent field capacity and severe deficit at 50 percent field capacity—with four foliar treatments: an untreated control, zinc oxide nanoparticles at 100 milligrams per liter, iron oxide nanoparticles at 100 milligrams per liter, and a combined zinc-plus-iron spray delivering 50 plus 50 milligrams per liter. These doses were deliberately selected to reflect concentrations that could plausibly be applied in the field rather than the exaggerated levels sometimes used in laboratory proofs of concept.

A defining feature of the work is the green synthesis route. Instead of relying on synthetic reducing and stabilizing agents, the researchers used an aqueous extract of common sage (Salvia officinalis) to convert metal salt precursors into zinc oxide and iron oxide nanoparticles. Plant extracts are rich in polyphenols, flavonoids, and other biomolecules that can both reduce metal ions and cap the growing particles, making the process cleaner, cheaper, and more compatible with sustainable agriculture. The resulting nanoparticles were characterized using scanning electron microscopy paired with energy dispersive X-ray spectroscopy, which confirmed particle morphology and elemental composition, ensuring that what reached the basil leaves were genuine nano-scale zinc and iron oxide materials rather than aggregated bulk powders.

The growth results were unambiguous. Under the 50 percent field capacity regime, untreated basil plants suffered the expected stunting and tissue loss, but nanoparticle supplementation substantially mitigated the damage. Compared with drought-stressed controls, nanoparticle-treated plants grew up to 26.7 percent taller, produced 30.6 percent more leaves, and accumulated 22.6 percent more biomass. Those are not marginal effects; they represent a meaningful recovery of canopy and yield potential in plants enduring nearly half their normal water allocation. For a high-value herb marketed on leaf quality and aromatic intensity, preserving leaf number and biomass under deficit irrigation has direct agronomic and economic significance.

Beneath the visible growth rescue lies a detailed biochemical story about reactive oxygen species. When stomata close to conserve water, photosynthetic electron transport becomes unbalanced and chloroplasts, mitochondria, and peroxisomes leak electrons onto oxygen, generating superoxide radicals and hydrogen peroxide. Left unchecked, these molecules attack membranes and produce malondialdehyde, a canonical marker of lipid peroxidation. In the nanoparticle-treated drought plants, the oxidative burden dropped dramatically: malondialdehyde and hydrogen peroxide levels each fell by nearly 50 percent relative to untreated drought controls, evidence that the sprays had re-equilibrated the plant’s redox state rather than merely masking stress symptoms.

The mechanism behind that protection differed between the two metals, and this is where the study makes its most interesting contribution. Zinc primarily strengthened the non-enzymatic antioxidant arm of the defense system. Zn-treated plants showed a 135 percent increase in cupric reducing antioxidant capacity, a 48 percent increase in ferric reducing antioxidant power, and a 17 percent increase in DPPH radical-scavenging activity compared with drought controls. These assays collectively indicate an expanded pool of small-molecule antioxidants—phenolics, flavonoids, and related compounds—that can chemically neutralize radicals before they damage cells. Consistent with that, the combined zinc-plus-iron treatment lifted total phenolic content by 53 percent and flavonoid content by 48 percent, effectively arming basil with a denser chemical shield.

Iron, by contrast, emerged as the enzyme specialist. Fe-treated plants recorded a 27 percent increase in superoxide dismutase activity, the front-line enzyme that dismutates superoxide radicals into hydrogen peroxide. Meanwhile, the combined treatment produced the most dramatic enzymatic activation of all: catalase activity surged by 204 percent and ascorbate peroxidase by 86 percent relative to drought controls. Catalase and ascorbate peroxidase are precisely the enzymes responsible for detoxifying the hydrogen peroxide that superoxide dismutase generates, so the combined spray appears to have coordinated a complete detoxification pipeline—converting dangerous radicals into hydrogen peroxide and then efficiently splitting that peroxide into water and oxygen. The two nutrients thus act on complementary arms of the antioxidant system rather than redundantly.

Statistical analysis reinforced this interpretation. Correlation analysis revealed strong positive associations among antioxidant capacity, photosynthetic pigment levels, and growth traits, suggesting that plants with the most robust redox buffering also preserved their chlorophyll and built the most biomass. Principal component analysis separated the treatment groups in multivariate space, with zinc-plus-iron-treated plants clustering distinctly within an antioxidant-rich, high-biomass region. That clustering pattern is the statistical fingerprint of coordinated redox regulation: rather than a scattered collection of independent biochemical changes, the nanoparticle treatments triggered an integrated physiological program linking pigment stability, antioxidant mobilization, and growth maintenance.

The practical implications extend beyond basil. Zinc and iron are essential plant micronutrients whose deficiency is widespread in agricultural soils worldwide, and foliar delivery of them as nanoparticles offers dual benefits: correcting micronutrient nutrition and priming stress defenses in a single intervention. The green synthesis route adds another layer of appeal, since sage extract is inexpensive, non-toxic, and readily available, and the process avoids the hazardous solvents associated with conventional nanomaterial manufacture. The concentrations tested—100 milligrams per liter for single-metal sprays and a 50 plus 50 split for the combination—are within ranges already considered field-applicable, which lowers the barrier to eventual on-farm trials.

Caveats remain, as the authors themselves frame the work as greenhouse-scale evidence rather than a finished field prescription. Open questions include how nanoparticle sprays behave under open-field UV and rainfall, how repeated applications affect soil microbial communities, whether nanoparticles accumulate in the harvested leaves and at what levels, and how the treatment interacts with the essential oil profile that gives basil its market value. Nonetheless, the study provides rigorous physiological and biochemical evidence that nanoparticle-mediated modulation of stress responses is real, measurable, and mechanistically coherent. As droughts deepen and water for irrigation grows scarcer, the idea that a few milligrams of sage-made zinc and iron, misted onto leaves, can cut a plant’s oxidative damage in half while boosting its antioxidant machinery by double digits is precisely the kind of elegant, testable solution that modern stress physiology has been looking for—and it suggests that the future of drought resilience may be not only in the genome, but in a spray bottle.

Subject of Research: Green-synthesized zinc and iron oxide nanoparticles enhancing drought tolerance in basil through antioxidant regulation

Article Title: Green-synthesized zinc and iron nanoparticles enhance basil drought tolerance via antioxidant regulation

Article References: Selvikaya, I., Karataş, R., Karakuş, M., Yilmaz, H., Demirel, F., Güler, E., Tutar, Y., & Yilmaz, A. (2026). Green-synthesized zinc and iron nanoparticles enhance basil drought tolerance via antioxidant regulation. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09935-3

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09935-3

Keywords: basil, drought stress, green synthesis, zinc oxide nanoparticles, iron oxide nanoparticles, antioxidant defense, catalase, superoxide dismutase, foliar application, Ocimum basilicum, redox regulation, stress physiology