Influence of extraction methods and temperature on hemp seed oil stability: A comprehensive quality assessment

Hemp seed oil's increasing popularity demands a comprehensive understanding of the impact of processing on its quality and stability. This study investigated the effects of extraction methods (hydraulic pressing, Bligh and Dyer method, and Soxhlet extraction) combined with storage temperatures (45 degrees C and 55 degrees C) on oil characteristics over 60 days. The oil extraction processes were conducted using standard protocols, followed by storage under controlled conditions. Analysis encompassed color changes, oxidation indicators (peroxide value, p-anisidine value, TBARS), free fatty acids, moisture content, and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy for molecular-level changes. Hydraulic press extraction demonstrated superior stability with minimal linoleic acid reduction (0.75 %) compared to Bligh and Dyer method (1.43 %) at 55 degrees C (p < 0.05) and Soxhlet extraction method (1.09 %). Higher storage temperature (55 degrees C) accelerated quality degradation significantly faster than 45 degrees C (p < 0.05), affecting oxidation markers and sensory attributes. Color darkening intensified at elevated temperatures, particularly in Bligh and Dyer extracted oils. ATR-FTIR spectroscopy analysis revealed significant changes in characteristic bands (2923.78 and 2854.07 cm-1), with hydraulic press-extracted oils showing better stability in peak intensities at 45 degrees C compared to other methods at 55 degrees C (p < 0.05). While most fatty acids remained stable, polyunsaturated fatty acids showed temperature and extraction-dependent degradation. These findings highlight the critical role of extraction method selection and temperature control in preserving hemp seed oil quality, suggesting hydraulic pressing as the preferred commercial extraction method. Implementation of appropriate storage conditions and the potential incorporation of natural antioxidants could further enhance oil stability.