Extract Process Optimization and Component Analysis of Pumpkin Seed Oil by Continuous Phase Transition Extraction

In order to efficiently extract pumpkin seed oil and fully realize its application value, continuous phase transition extraction (CPE) was applied to extract pumpkin seed oil in this study. The effects of extraction temperature, extraction time, extraction pressure and separation temperature on the extraction efficiency of pumpkin seed oil were studied with extraction rate and content of active ingredients as indicators. The optimum extraction process parameters were determined by response surface design. The results were compared with supercritical fluid extraction (SFE) and screw pressing (SP) methods in terms of extraction rate, active ingredient content, physicochemical properties, and fatty acid composition of pumpkin seed oil. The results showed that the optimum extraction process parameters of pumpkin seed oil by CPE were obtained as follows: Extraction temperature of 46 ℃, extraction time of 72 min, extraction pressure of 0.51 MPa and separation temperature of 65 ℃. Under these process parameters, the extraction rate of pumpkin seed oil reached 96.75%, which was 14.49% and 35.24% higher than SFE and SP, respectively. The contents of total phenols, carotenoids, sterols and zinc were 1333.80 mg/kg, 8.41 mg/kg, 2.59 mg/g and 9.61 mg/100 g, respectively. These values were 1.56, 2.29, 1.17 and 1.40 times higher than SFE, and 1.54, 2.56, 1.89, and 2.46 times higher than SP, respectively. The pumpkin seed oil obtained by CPE was a clarified transparent and viscous liquid, with a delicate fragrance. Its physicochemical indicators of acid value, iodine value, and peroxide value met the requirements of LS/T 3250-2017 standard. Seven kinds of fatty acids were identified by gas chromatography-mass spectrometry (GC-MS). Linoleic acid and oleic acid accounted for 82.32% of the total fatty acid content, which was 5.66% and 8.99% higher than SFE and SP, respectively. This study showed that CPE could effectively alleviate the degree of oxidative rancidity of oil and increase the content of unsaturated fatty acids while taking into account the extraction rate and active ingredient content of pumpkin seed oil, which provided a reference for the industrial continuous production of highly active pumpkin seed oil.