Effect of Cold Plasma-Treated Turmeric on the Oxidative Stability and Quality of the Oil From the Milk Thistle Seeds

Abstract

Many studies have been carried out on the antioxidant effects of medicinal plants in edible oils. One of those plants is turmeric, which, due to its biological and antioxidant compounds such as curcuminoids, has a strong antioxidant effect and prevents oxidation of unsaturated fatty acids (FAs). In this study, turmeric at different levels (5% and 10% w/w) was used to increase the oxidative stability of the milk thistle (Silybum marianum L.) seed oil (MTSO). Additionally, to improve the performance of turmeric, cold plasma (CP) treatment was used at different durations (5 and 10 min). The effect of turmeric on the quality parameters of MTSO was investigated during different storage times (1, 30, and 60 days). The results indicated that the addition of turmeric treated with CP significantly (p < 0.05) decreased the acidity value (AV) (1.00–0.62 mg NaOH/g oil) and the peroxide value (PV) (4.47–3.65 mEq O₂/kg oil) and also increased the total phenolic content (1003.23–1116.90 mg/GAE/100 g oil), antioxidant activity, α-tocopherol, and finally the oxidative stability compared to the control sample and oil containing untreated turmeric. Furthermore, gas chromatography (GC) analysis of the oil sample of the FA profile containing CP-treated turmeric revealed the higher ratio of unsaturated FAs (i.e., linoleic and arachidonic acid) and lower saturated FA content (palmitic and stearic acid) compared to oil samples containing untreated turmeric. To conclude, CP treatment increased turmeric performance and improved the quality characteristics of MTSO.