Oxidative Stability of Cooking Oil Blend Stabilized with Leaf Extract of Eucalyptus citriodora

Abstract

The present study was conducted to assess the effects of Eucalyptus citriodora (E. citriodora) leaf extract on the oxidative stability of blend of canola, rapeseed, and sunflower oils (45:20:35 v/v, respectively) under accelerated storage. The blended oil was stabilized with 300 mg/L ethanolic extract (source of total phenolic content and total flavonoid content [5.23 ± 0.19 and 1.18 ± 0.04 g/100 g d.wt. of extract]) of E. citriodora leaves. The oxidative stability was measured on the basis of parameters such as free fatty acid contents, peroxide value, sponification value, iodine value, color, cloud point, and refractive index. After a 100 day incubation period, the increase in refractive index, free fatty acid, and peroxide, and sponification values in stabilized and non-stabilized oil blends were 0.0028 and 0.0047, 0.20 and 2.37% as oleic acid, 12.54 and 21.12 meq/kg of oil and 10.04 and 17.01 meq of KOH/g of oil, respectively, as compared with initial values. However, a decrease of 10.0 and 16.9 g of iodine/100 g of oil was recorded in oil iodine values of both stabilized and non-stabilized blended vegetable oils. Results showed that E. citriodora leaf extract was found effective to maintain the oxidative stability of blended vegetable oils for long duration (6 months) as compared with control oil samples. Therefore, it can be concluded that E. citriodora leaf extract is a cheap rich source of natural antioxidants that can be easily used for the stabilization of vegetable oils in the food processing industries.