Evaluation of the Quality of Two Commercially Available Edible Oils in Arba Minch, Ethiopia

The physicochemical properties and extent of oxidative alterations in commercially available sunflower and palm oils subjected to ambient and sunlight storage conditions were analyzed using different physicochemical parameters. The result of physico-chemical properties shows that acid value (mg KOH/gm), peroxide value (meq/kg of oil), conjugated diene (g-1cm-1 mL), specific gravity (gmmL), refractive index and pH for sunflower oil are 3.366±0.5610, 1.933±0.7023, 3.166±0.0014, 0.9261±0.0005, 1.451±0.001 and 6.850±0.0015 respectively and for palm oil are 3.179±0.3238, 5.733±0.4618, 1.533±0.0080, 0.904±0.0001 and 7.184±0.0051 respectively. Peroxide and specific gravity values were within the acceptable rage set by CONDEX standards whereas acid value, refractive index and conjugate diene were not within the acceptable rage and also cholesterol is detected in both oils. The magnitude of oxidative changes subjected to ambient and sunlight storage for 24 days was monitored by the periodical measurement of peroxide value, acid value and conjugated diene value. The acid value, conjugate diene and peroxide value of Sunflower oil (SFO) subjected to ambient storage condition were found to be 3.366±0.561 mgKOH/gm, 3.166±0.0144 g-1cm-1 mL and 2.066±0.9018 meq/kg of oil respectively and this value is reached to 16.269±0.5611, 3.85±0.025 and 10.200±0.800 at the end of the storage period. But for sunlight storage condition this value is reached to 22.253±0.3238, 5.125±0.0250 and 12.666±0.3055 respectively. The values of palm oil subjected to ambient storage condition were found to be 17.578±0.8569 mgKOH/gm, 2.416±0.0320 g-1cm-1 mL and 14.066±0.6110meq/kg of oil respectively for acid value, conjugate diene and peroxide value and this values were raised to 24.123±0.561, 3.025±0.0250 and 16.133±0 when subjected to sunlight storage condition. Generally, with respect to standard requirement for physicochemical quality of cooking oils as specified by the Codex Alimentarius Commission(CX-STAN210-1999) the acid value, conjugated diene and refractive index value of both sunflower and palm oils are not in acceptable rage and it indicates there is possible rancidity in the oil sample.