Toxicologie environnementale et analytique

Comparative Study of the Physicochemical Properties of Adulterated, Unadulterated, Crude and Bleached Palm Oil Samples

Abstract

Ngozi Jane Maduelosi*, E. G. Kingsly, C.M. Ekezie and J.U. Okwechime

The physicochemical properties of adulterated, unadulterated, crude and bleached palm oil samples were determined so as to access the impact of additives and bleaching on the oil samples. The adulteration was done by introducing Sudan dyes (azo dyes) in the sample. Physical properties of the samples, such as Free Fatty Acid (FFA), moisture content, peroxide value, Specific Gravity (S.G) and colour were measured using standard methods. Fourier Transform Infra-Red (FTIR) Spectroscopy was also carried out on the oil samples to determine the effects of the dye and bleaching on the chemical composition of the samples. From the results obtained, the values of the physical properties measured were higher in the adulterated samples than in the unadulterated samples. The value of the Free Fatty Acid (FFA) for Crude Unadulterated Palm Oil (CUPO) was 10.67% and that of the Crude Adulterated Palm Oil (CAPO) was 16.46% wherein the Nigerian Industrial Standards (NIS) value is 5.0 max. The value of the FFA for the adulterated palm oil was higher than that of the unadulterated palm oil sample, in which both did not fit into the standard. The FFA values of the Bleached Unadulterated Palm Oil (BUPO) were 7.75% and Bleached Adulterated Palm Oil (BAPO) was 14.64% which are within the range of the NIS permissible limit.

Moisture content values for CUPO was 0.69%), CAPO=0.79%, BUPO - 0.28% and that of BAPO was 0.45%. The NIS limit is 0.5max, so the values of CUPO and CAPO are above the limit. For the Peroxide values, CUPO had a value of 5.81 Meq/kg, CAPO=17.77 Meq/kg, BUPO=3.40 Meq/kg and that of BAPO was 12.69 Meq/kg, against the NIS of 10 Meq/kg. The values of the specific gravity of the different samples are: 0.905 for CUPO, 0.909 for CAPO, 0.911 for BUPO and 0.906 for BAPO. The values were all above the NIS standard value of 0.901. For the colour, CUPO and BUPO were within the NIS range while the values for CAPO and BAPO were over the maximum, whereas the values for the unadulterated sample were within the Nigerian Industrial Standard. The FTIR results revealed that unsaturation in the oil is lost by the reaction of the fatty acids in the oil with the dyes. Bleaching also results to bond breakages in the oil samples, therefore, adulteration destroys the quality of palm oil.