Main content area

Oxidative stability of enriched walnut oil with phenolic extracts from walnut press-cake under accelerated oxidation conditions and the effect of ultrasound treatment

Bakkalbaşı, Emre
Journal of food measurement & characterization 2019 v.13 no.1 pp. 43-50
alpha-tocopherol, antioxidants, maceration, oxidation, oxidative stability, phenolic compounds, ultrasonic treatment, ultrasonics, walnut oil, walnuts
In this study, the effect of phenolic extract obtained from walnut press-cake on oxidative stability of walnut oil was evaluated. Besides this, the oxidative stability of ultrasound applied walnut oil with added press-cake, as a valuable source of phenolic compounds, was determined. Oxidative stability of walnut oils upon addition of phenolic extracts (50, 100 and 200 mg/kg oil) and α-tocopherol (100 mg/kg oil) was monitored under accelerated oxidation conditions at 65 °C for 20 day. Total phenolic content (TPC) of walnut press-cake and phenolic extract from walnut press-cake were 58207.3 and 332679.8 mg GAE/kg, respectively. All concentrations of phenolic extracts significantly reduced the formation of oxidation products compared to control. Especially, the walnut oils enriched with 200 mg/kg phenolic extract showed the highest oxidative stability. While direct enrichment using ultrasonic maceration (1:100) (walnut press-cake:walnut oil) caused a significant increase in TPC of walnut oil (from 9.76 to 78.80 mg GAE/kg), ultrasonic macerated walnut oil had low oxidative stability. Results showed that 200 mg/kg oil phenolic extracts from walnut press-cake can be successfully used as a natural antioxidant preparate to improve the oxidative stability of walnut oil.