The motivation behind the study reflects a broader shift in the food industry. Synthetic antioxidants such as butylated hydroxytoluene, or BHT, have been workhorse additives for decades, but growing safety and regulatory concerns have pushed manufacturers to seek plant-based alternatives. Essential oils from aromatic plants are attractive candidates because they are biocompatible and biodegradable, and mastic resin in particular is known to be rich in bioactive terpenes. The problem has always been the extraction. Conventional hydro-distillation and steam distillation subject delicate compounds to prolonged heating in the presence of water and oxygen, which can degrade heat-labile molecules and strip away antioxidant activity before the oil ever reaches the bottle. Long processing times and high fuel costs compound the difficulty.

Superheated steam extraction offers a way around these limitations. The technique uses steam heated to between roughly 101 and 180 degrees Celsius, well above the temperature at which water would condense. This dry vapor carries very little oxygen but conducts heat efficiently, and at elevated temperatures its low polarity and altered dielectric properties help it pull out both non-polar and polar constituents from plant tissue. The intense heat also helps rupture plant cell walls, releasing volatile molecules that conventional methods leave behind. The approach has previously been applied to thyme, black pepper, and frankincense resin, but no one had systematically optimized it for mastic resin with the goal of maximizing antioxidant capacity.

To do so, the team, led by Muhammad Adnan Ayub of the University of Okara, combined the extraction technology with response surface methodology, a statistical framework that maps how multiple variables interact to shape an outcome. Using a central composite design, they ran eighteen experimental combinations spanning extraction temperatures of 140 to 180 degrees Celsius, extraction times of 90 to 150 minutes, and resin particle sizes of 0.5 to 1.0 millimeters. Each run was performed in triplicate, and the resulting oils were tested with three complementary antioxidant assays: DPPH free-radical scavenging, ferric reducing antioxidant power, and hydrogen peroxide scavenging.

The statistical analysis revealed a clear optimum at the midpoint of the design space. At 160 degrees Celsius, 120 minutes, and 0.75 millimeter particles, the oil achieved a DPPH radical-scavenging activity of 88.64 percent, a ferric reducing power of 120.54 milligrams per 100 grams, and a hydrogen peroxide scavenging activity of 78.64 percent. The quadratic models fitted to these responses explained more than 96 percent of the variation in the DPPH and hydrogen peroxide data, and the gap between adjusted and predicted coefficients of determination stayed below the 0.2 threshold that signals a trustworthy predictive model. Adequate precision values, a measure of signal to noise, exceeded 4 for all three responses, confirming that the models could reliably navigate the experimental range.

The shape of the response surfaces tells a chemically sensible story. Moderate temperatures outperform both extremes: at 160 degrees Celsius, the kinetic energy of the system is high enough to vaporize and release essential oil molecules efficiently, yet the heat-sensitive antioxidant compounds are not yet pushed into thermal decomposition. Extraction time follows a similar arc. Activity climbs as antioxidants diffuse out of the resin over the first two hours, but beyond that point the process begins co-extracting less desirable components that dilute the antioxidant fraction, so activity declines. Particle size proved counterintuitive. Rather than the finest grind winning, the intermediate 0.75 millimeter fraction performed best. Over-grinding, the authors note, can alter surface characteristics and produce unusable fines, while larger particles limit the surface area available for mass transfer.

When the optimized superheated steam oil was compared head-to-head with oils from conventional hydro-distillation and steam distillation, the advantage was unmistakable. Hydro-distillation yielded the weakest oil, with 71.56 percent DPPH scavenging, 101.12 milligrams per 100 grams of ferric reducing power, and 66.79 percent hydrogen peroxide scavenging. Steam distillation landed in the middle at 76.71 percent, 108.62, and 71.41 respectively. The superheated steam oil topped all three measures, approaching but not exceeding the performance of the synthetic and pure-compound standards BHT, gallic acid, and ascorbic acid used as benchmarks in the assays.

Gas chromatography-mass spectrometry explained why. The superheated steam oil contained 98.41 percent identifiable compounds, compared with 94.71 percent for steam-distilled oil and 90.18 percent for hydro-distilled oil, and it was markedly richer in alpha-pinene, which rose from 49.5 percent in the hydro-distilled oil to 60.3 percent in the superheated steam product. Alpha-pinene, the dominant monoterpene, scavenges free radicals by donating hydrogen atoms to stabilize them. Limonene suppresses lipid peroxidation and neutralizes reactive oxygen species, while beta-myrcene and cis-verbenone contribute through electron donation and metal chelation. Verbenol, an oxygenated monoterpene, carries a reactive hydroxyl group that reacts directly with radicals. Together these five constituents, alpha-pinene, verbenol, cis-verbenone, limonene, and beta-myrcene, form the chemical backbone of the oil’s antioxidant power.

The composition shifts also reveal the chemistry happening inside the extractor. Under heat, alpha-pinene can partially oxidize first to verbenol and then to cis-verbenone, which is why the proportions of these oxygenated derivatives differ across methods. Hydro-distillation, running at lower temperatures, preserves thermolabile compounds but extracts them inefficiently because of constant water contact. Steam distillation offers a moderate compromise. Superheated steam, with its dry heat and higher temperature, ruptures cell walls more aggressively and drives a fuller release of volatiles, which shows up both in the total identified compound percentage and in the antioxidant assays.

For the food and nutraceutical industries, the implications are practical. The study demonstrates that extraction method is not a neutral variable but a lever that can be tuned to concentrate functional activity, and it provides manufacturers with validated operating conditions for producing an antioxidant-rich mastic oil without solvents. The resin itself was harvested by tapping a mature tree in the semi-arid Zhob District of Baluchistan, Pakistan, and authenticated with a voucher specimen, underscoring the botanical traceability behind the chemistry. The authors caution that more work is needed to establish the oil’s efficacy in real food matrices and to optimize additional parameters of the superheated steam process, including energy consumption at scale. But the central finding stands: a green, solvent-free extraction technology can coax measurably more antioxidant value out of one of the Mediterranean’s oldest natural products, and statistical design made that optimum visible.

Subject of Research: Optimization of superheated steam extraction for antioxidant-rich Pistacia lentiscus oleo-gum resin essential oil

Article Title: Improved Antioxidant Properties of Pistacia lentiscus L. Oleo‐gum Resin Essential Oil Extracted by Superheated Steam: Process Optimization and Chemical Characterization

Article References: Ayub, M. A., Iram, I., Mammadova, K., Mohammed, O. A., Waseem, R., Ramadan, M. F., Zubair, M., Abbas, M., & Choobkar, N. (2026). Improved Antioxidant Properties of Pistacia lentiscus L. Oleo‐gum Resin Essential Oil Extracted by Superheated Steam: Process Optimization and Chemical Characterization. Food Science & Nutrition, 14(10), Article e72383. https://doi.org/10.1002/fsn3.72383

Image Credits: AI Generated

DOI: 10.1002/fsn3.72383

Keywords: Pistacia lentiscus, essential oil, superheated steam extraction, antioxidant activity, response surface methodology, DPPH, FRAP, alpha-pinene, GC-MS, green extraction, food science, mastic resin