Comparative quality assessment of two oils from Elaeis guineensis in Juaben Municipality, Ghana.

Abstract

This study aimed at comparatively assessing the quality of two oils from Elaeis guineensis in the Juaben Municipality, in terms of their heavy metal content and physicochemical properties. Five samples each of the two oils which is palm and kernel oils were randomly collected in triplicates from five different small-scale oil palm processing sites in the Municipality for the study. The samples were subjected to heavy metals and physicochemical parameters analysis. The level of heavy metals (Fe, Cu, Zn, Cd, As, and Pb) were determined by atomic absorption spectrophotometric method after wet digestion and the physicochemical parameters such as saponification value, acid value, ester value, percentage free fatty acid, percentage moisture, odour, and Lovibond colour were carried out by standard methods. The heavy metals content in both samples ranged as follows; Fe (0.940 to 15.022 mg/L), Cu (0.964 to 2.267 mg/L), Zn (0.988 to 16.348 mg/L), Cd (0.042 to 0.158 mg/L), As (0.265 to 0.456 mg/L) and Pb (0.205 to 0.503 mg/L) in palm oil samples and Fe (3.710 to 41.780 mg/L), Cu (1.414 to 41.919 mg/L), Zn (1.092 to 6.207 mg/L), Cd (0.030 to 0.232 mg/L), As (0.122 to 0.494 mg/L) and Pb (0.105 to 0.268 mg/L) in palm kernel oil samples. The concentrations of heavy metals in all samples across the sampling sites were generally higher than the permissible levels by FAO/WHO except for cadmium. Statistical analysis of levels of the studied metals in palm and kernel oil samples showed a weak negative correlation in terms Cd, moderate negative relationship with regards to Fe, strong negative correlation in terms of Cu, and a very strong positive correlation in terms of Zn, As, and Pb. A t-test also revealed no statistically significant difference in terms of Fe, Cu, Zn, and Cd while a statistically significant difference was observed in As and Pb in both oils. The relative ranges of the physicochemical parameter values obtained were as follows; saponification values (192.960 to 216.320 mgKOH/g), acid value (12.973 to 28.300 mg KOH/g), ester values (166.650 to 198.045 mgKOH/g), percentage free fatty acid (6.857 to 15.091 %), %moisture Content (0.140 to 0.530 %), and Lovibond colour (17R + 27Y to 28R + 33Y) for palm oil samples and saponification values (230.410 to 260.740 mgKOH/g), acid value (8.816 to 25.085 mg KOH/g), ester values (212.677 to 246.049 mgKOH/g), percentage free fatty acid (3.014 to 13.245%), %moisture content (0.150 to 0.680 %), and Lovibond colour (21R + 25Y to 27R + 33Y) for palm kernel oil samples. The physicochemical parameters significantly varied (P< 0.05) across all sampling sites. In comparison to recommended standards, acid value, percentage free fatty acid, percentage moisture content, and Lovibond colour levels recorded were above the stipulated standards except for saponification values, and ester values. A statistical analysis showed a moderate correlation in saponification value, and ester value, moderate negative relationship in percentage moisture, a very strong negative correlation in terms of acid value and a strong correlation in percentage free fatty acid value in both oils. On a t-test, a significant statistical difference was observed in ester and saponification values whereas no statistically significant difference was observed in acid value, percentage free fatty acid and percentage moisture value in both oils. Consequently, the study's findings demonstrated that the palm and kernel oils produced by these small-scale processors do not satisfy the quality standards for dietary use, and can pose health threat to customers. Therefore, to ensure public food and health safety, regulatory bodies should bolster their supervision.