Microwave-Assisted Extraction of Hemp Seed Oil: Process Optimization for Enhancing Oil Yield and Bioactive Compound Extractability.

Hemp seed oil is a valuable source of unsaturated fatty acids. However, its high degree of unsaturation makes it highly susceptible to oxidation, which can compromise its quality and nutritional value. Enhancing its stability can be achieved by incorporating antioxidant compounds naturally present in the seeds. A deeper understanding of the interactions between the extraction process and the oil's composition would provide valuable insights for optimizing both its stability and bioactive properties. In this context, this study was aimed at investigating and optimizing the microwave-assisted extraction of hemp seed oil, enriched with bioactive compounds, using response surface methodology. Three extraction factors were investigated: microwave power (600, 750, and 900 W), cosolvent percentage (0%, 5%, and 10% ethanol relative to hexane), and extraction time (5, 10, and 15 min). Several responses were studied, including oil yield, total phenolic content (TPC), total tocopherols, oxidative stability index (OSI), chlorophylls, carotenoids, quality indices (peroxide value and conjugates [diene and triene]), and color (L∗, a∗, b∗, C∗⁣_ab, and h _ab). The optimum extraction conditions were 800 W, 7.5% EtOH, and 13.60 min, reaching a maximum yield of 30.69%. The resulting oil showed a high OSI (28.60 h) and a richness in TPC, tocopherols, carotenoids, and chlorophylls (88.55, 510.64, 27.21, and 99.68 mg/kg oil, respectively) along with an acceptable oxidation quality and intense color parameters (L∗ = 33.54, a∗ = -4.01, and b∗ = 3.17). Furthermore, a detailed analysis of phenolic compounds using HPLC-DAD/ESI-MS was carried out on microwave-extracted oils. The finding showed that both variables (power and %EtOH) resulted in notable fluctuations in the phenolic profile of the extracted oil. The contents of phenolic acids (13.48 mg/kg), hydrocinnamic acid amides (9.97 mg CTE/kg), and lignanamides (16.18 mg CTE/kg) identified in the hemp seed oil were highest under 600 W, 10% ethanol, and 10 min.