Effects of different extraction methods on extraction effect and functional properties of Korean pine seed oil

  Objective  Based on solvent method, by comparing the yields of Korean pine seed oil separately treated by ultrasonic method, microwave method or light wave method, and the soaking yields of Korean pine seed oil after separate method treatment, the dominant method in the extraction process of Korean pine seed oil was identified. At the same time, the effects of four extraction methods on physicochemical indexes, fatty acids and antioxidant capacity of Korean pine seed oil were confirmed.

  Method  According to the GB/T 5009.229−2016 Determination of Acid Value in Food, GB/T 5532−2008 Determination of Iodine Value of Animal and Vegetable Oils and GB/T 5009.227−2016 Determination of Peroxide Value in Food, the acid value, iodine value and peroxide value of Korean pine seed oil extracted by the four methods were determined. The type and mass fraction of fatty acids in Korean pine seed oil were determined by gas chromatography-mass spectrometry method, and the scavenging abilities of Korean pine seed oil to DPPH· and ABTS⁺· were determined by spectrophotometry.

  Result  The optimum extraction solvent was n-hexane. When the extraction temperature was 25 ℃, the liquid to solid ratio was 18 mL/g, the extraction time was 5 h, the yield of Korean pine seed oil was 65.52%. The yield of Korean pine seed oil was 67.63%, 62.26% and 58.25% by ultrasonic (300 W, 10 min), microwave (380 W, 100 s) and light wave (400 W, 11 min), respectively. After the three methods treated separately and the extraction was carried out with n-hexane individually, the yield increased by 2.18%, 4.50% and 6.10%, respectively after the total time reaching 5 h. The Korean pine seed oil extracted by the four methods can meet the limit standard of acid value (≤ 4 mg/g) and peroxide value (≤ 0.25 g/100 g) in GB/T 2716−2018 National Food Safety Standard Vegetable Oil. The acid value and peroxide value of Korean pine seed oil prepared by organic solvent method were the lowest (P < 0.05). The mass fractions of fatty acid from high to low were linoleic acid (44.54% − 46.32%), oleic acid (28.29% − 28.83%) and pinocyanic acid (13.15% − 14.51%). The DPPH· and ABTS⁺· IC₅₀ values of Korean pine seed oil extracted by solvent, ultrasonic, microwave and light wave methods were 9.41, 8.80, 9.43, 9.61 g/L and 5.10, 5.51, 6.10, 5.43 g/L, respectively.

  Conclusion  The yields of ultrasonic method, microwave method or light wave method separately, and soaking yields after the single treatment were compared. It is found that ultrasonic, microwave and light wave method play a leading role in the extraction process. Compared with the solvent method, microwave method and light wave method, Korean pine seed oil extracted by the ultrasonic method has a higher extraction percentage, a higher mass fraction of unsaturated fatty acid, a stronger antioxidant capacity, and can achieve better extraction effect. This method has some advantages in the Korean pine seed oil extraction industry.