Physicochemical parameters and heavy metal content in soybean oil from Bangladesh

Abstract

Nine familiar brands of soybean oil were selected to assess the quality of oil using standard methods of analyses. All branded oil showed satisfactory results regarding physical parameters such as moisture content, specific gravity and viscosity. However deviation from standard requirements was observed for most of the chemical parameters. Comparatively low iodine value was noticed and the values varied from 110±3.0 to 114±2.2 g/100 g oil. Saponification value was found in the range of 200±2.9 to 210±1.6 mg KOH/g which was relatively high. Five branded oil out of nine had reasonably high acid value. Peroxide value was found in acceptable range (0.85-1.42 meq/kg oil) but the value was increased rapidly by 91.2% on an average during five months storage. Cholesterol was detected in all samples and the concentration ranged from 220±0.7 to 505±2.1 mg/100 g oil. Lead (Pb), nickel (Ni), cadmium (Cd) and copper (Cu) contents were determined in Crude Degummed Soybean oil (CDSO) and in 9 different brands of soybean oils using atomic absorption spectrophotometer (AAS) after wet digestion. The accumulation trend for soybean oil was in the following order Cu>Ni>Pb>Cd. The concentration of Pb, Ni and Cu in some brands was found to be higher than the recommended legal limits. However, the estimated intakes of Pb, Ni and Cu from daily consumption of 25 g of the investigated oils should cause no risk to human health.