Phenolic compounds and some quality parameters of pumpkin seed oil

Pumpkin seed oil has become a recognized source of phenolic compounds. The main aim of this paper was to evaluate the concentration of phenolic compounds and their extraction from pumpkin seed oil. The total phenolics content (TPC) measured in the pumpkin seed oil samples ranged from 24.71 to 50.93 mg GAE/kg of oil. The individual phenolics were tyrosol, vanillic acid, vanillin, luteolin and sinapic acid. Hexane and acetone were the best solvents for the washing step, and methanol for the elution of the phenolics in the solid-phase extraction (diol-SPE), whereas bleaching caused a significant increase in the TPC obtained (24.5-30.7%). Additionally, some other oil characteristics were evaluated. The mean oxidative stability of the oils (OSI) was around 4 h, with 5.43 h for the most stable oil. The maximum antioxidant capacity measured by the reduction of the DPPH radical was 62%, which was comparable to 0.16 mM Trolox equivalent. The color of the oil was expressed by L(star)a(star)b(star) coefficients and its hue and saturation. Whereas all samples had similar lightness, their rates of green, red, yellow and blue color were different. Moreover, TPC correlated negatively with lightness, b(star) and saturation (-0.49, -0.48, and -0.43), and positively with a(star) and hue (0.58 and 0.52).

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