Investigating the oxidative stability of grape seed oil using aqueous extract of pistachio green hull

In this study, ultrasound assisted enzymatic aqueous extraction was implemented for extraction of phenolic compounds from pistachio green hull (PGH). To obtain this aim, ultrasonic time (10-25, 40 min), incubation time (60, 150, 240 min), cellulase enzyme (1, 4, 7 U/ml) and pectinase enzyme (1, 3, 5 U/ml) were optimized using completely randomized factorial design (CRD). The optimal extraction was 25 min of ultrasonic time, incubation time of 150 min and cellulase/pectinase ratio 3:4 U/ml. The value of extraction yield (EY), total phenol content (TPC), total tannin content (TTC), total anthocyanin content (TAC), DPPH, ABTS and FRAP of this treatment were 33.419 +/- 0.154%, 58.110 +/- 0.471 (mg GAE/g dw), 9.476 +/- 0.287 mg/g, 25.292 +/- 0.274 mg CY/g dw, 81.791 +/- 0.937%, 54.451 +/- 0.531% and 448.68 +/- 1.43 mu mol Fe2+/g dw respectively. Scanning electron microscopy (SEM) of this treatment confirmed more cracks and pores in the cell wall as compared to the control. Then the oxidative stability of grape seed oil containing the selected treatment (100 ppm) was estimated during 90 days of storage and compared to the sample containing synthetic antioxidant (100 ppm TBHQ) as well as the control by measuring induction time, peroxide value (PV), p-anisidine value (AV). Color and sensory analysis were also evaluated. According to the results, selected treatment retarded the oil oxidation. In terms of oil color assessment, sample containing PGH showed lower values of the parameters (L*, a*, b*) than the control. However, the overall acceptability of the selected sample was significantly higher than the control (p <= 0.05). Finally, water extract of PGH could be recommended as a natural antioxidant to control the oil oxidation with high quality.