IMPACT OF REFINING ON PHYSIOCHEMICAL, HEAVY METAL AND MINERAL PROFILES IN VEGETABLE OILS

Abstract

The present study was carried out to examine the changes in physiochemical properties, heavy metal and mineral concentrations after refining of soybean and palm oil. The results showed that specific gravity have decreased after refining process. The value of specific gravity ranged from 0.919-0.929 for crude soybean oil and 0.913-0.923 for refined soybean oil; 0.958-0.95 for crude palm oil and 0.938-0.95 for refined palm oil. Correspondingly, the chemical properties such as acid value, peroxide value, and saponification value were decreased and iodine value was increased. Peroxide values were 9.243 meq O2 /kg oil to 12.87 meq O2 /kg oil and 11.26 meq O2 /kg oil to 8.11 meq O2 /kg oil for crude soybean and palm oil respectively and decreased to 1.112 meq O2 /kg oil to 3.597 meq O2 /kg oil and 4.41 meq O2 /kg oil to 2.47 meq O2 /kg oil for refined soybean and palm oil. Comparatively low iodine value was noticed and the values varied from 117.96 to 120.66 g I2/100 g of oil for refined soybean oil. Iodine value for palm oil was found in acceptable range (66.75- 59.52 g I2/100 g). Saponification value was found in acceptable range 194.12-170.033 mg KOH/g and 195.27-189.76 mg KOH/g for refined soybean and palm oil respectively. Acid value was similar with standard value for both soybean and palm oil (0.647-0.271 mg KOH /g oil and 0.967- 0.76 mg KOH /g for refined soybean and palm oil respectively). Iron, copper, lead and cadmium were analyzed by using AAS. Refining of the samples decreased the concentration of heavy metals (Pb and Cd) and mineral (Fe& Cu). Concentrations of all trace metals were within the limits of the accepted values by regulatory bodies. Concentration of Fe was 1.24- 2.8 mg/L and 1.79-3.15 mg/L for refined soybean and palm oil samples respectively. Concentration of Pb and Cd were below detection limit in refined soybean and palm oil. Concentration of Cu was 0.193 -0.413 mg/L and 0.1 -0.357 mg/L for refine soybean and palm oil. Hence these oils were safe for human consumption.