Pumpkin (Cucurbita maxima) by‐products: Obtaining seed oil enriched with active compounds from the peel by ultrasonic‐assisted extraction

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Ultrasonic‐assisted extraction (UAE) of the oil from the seeds/peel mixture of pumpkin using ethanol as solvent was investigated. The effects of the ultrasound, solvent volume, time, and temperature on the oil yield were evaluated. Oil extraction from the seeds by ultrasound and the mixture by Soxhlet extraction (SE) was also performed. The use of ultrasound and higher availability of ethanol (up to 6 mL g−1 sample) favored the oil removal. In the extraction kinetics, the washing step was verified in the first 20 min, corresponding to 79–89% of the total oil yield. The diffusion coefficient increased from 30 to 75°C, as well as the spontaneity of the extraction, achieving 71% of the SE. Linoleic and oleic acids were found in higher concentrations in the oils. UAE made possible the greater extraction of β‐carotene, tocopherols, and fistosterois, and the peel addition provided higher contents of these compounds. Practical application The simultaneous extraction of compounds from the pumpkin by‐products arouses interest, for obtaining an oil of the seeds enriched with the active compounds present in the peel. Ultrasound‐assisted extraction was employed because it showed relevant benefits in relation to Soxhlet extraction, such as operations with reduced time, mild temperatures, and low amounts of solvent. Aiming at the use of solvents considered as “green,” in the present study we opted for the use of ethanol, since it is considered a safe solvent and comes from renewable sources. In addition, the determination of the diffusion coefficient and the thermodynamic properties of the process helped to understand the mechanisms that characterize the extraction.