Supercritical Carbon Dioxide Extraction: Antioxidant Activity and Lipid Composition of Hemp Seed Oil in Thailand

In this study, we examine the factors affecting the quality of supercritical carbon dioxide (SC-CO₂) extraction, as well as the antioxidant and lipid compositions of hemp seed oil from Thailand. Supercritical CO₂ extraction was conducted under different pressures (74–400 bar), temperatures (32°C–150°C), and extraction times (30–120 min) to evaluate their effects on hemp seed oil yield and antioxidant properties. Using the SC-CO₂ extraction technique on recently harvested hemp seeds (with an initial moisture content of ~7%–8% prior to oven drying), and under optimized conditions of 32°C, 400 bar, and 120 min, the process achieved an extraction yield of 26.26% ± 0.24% (dry weight basis). This corresponds to 85.82% of the yield obtained through hexane extraction. The total phenolic content reached its peak, measuring 163.2 ± 0.4 mg GAE/g extract. The antioxidant activity, assessed from the DPPH radical scavenging activity, displayed the most favorable results, with an IC₅₀ of 1.5 ± 0.1 mg/mL. Furthermore, the recently harvested hemp seed samples contained a significant quantity of cannabidiol, measuring 0.22 mg/g. Additionally, the FRAP of extract from recently harvested hemp seeds exceeded that from dry seeds (moisture 1%–2%), measuring 148.6 ± 1.4 and 139.3 ± 0.3 μmol FeSO₄/g extract, respectively. These results highlight that hemp seed extract is a rich source of polyunsaturated fatty acids, constituting 72.91% of the content, with linoleic acid (C18:2n6c) having the highest 51.45% concentration.