Evaluation of trace metals and quality of selected brands of vegetable cooking oils available on the Ghanaian market

Abstract

Background

Vegetable cooking oils are important ingredients for the cooking of food in every Ghanaian kitchen. The scarcity of studies on potentially toxic metals, and physicochemical properties in vegetable cooking oils globally necessitated this investigation. This study aims to contribute to consumer awareness by assessing the quality and safety of vegetable cooking oils in the Ghanaian market.

Methods

Vegetable cooking oils were obtained from Ayigya market, a popular and busy open-air market located in Kumasi, Ghana. Physicochemical parameters such as refractive index, acid, iodine, saponification, and peroxide values and trace metals such as Pb, Cd, Zn, Ni, Cr, As, Ca, and Fe were analyzed using standard analytical methods and flame atomic absorption spectrophotometer.

Results

The findings showed an acid value ranging from 0.817 to 1.699 mgKOH/g, iodine value, from 60.680 to 122.300 gI₂/100 g, peroxide value from 10.890 to 34.730 meq/kg, saponification value from, 189.060 to 202.310 mgKOH/g, and refractive indice ranged from 1.463 to 1.471, respectively. Concentrations of potentially toxic metals such as Ni, Cr, As, Pb, and Cd in all cooking oils were below detection limits. Concentrations of Fe, Zn, and Ca were found within the range of 1.690 to 2.480 mg.L⁻¹, 0.014 to 0.048 mg.L⁻¹, and 0.118 to 1.328 mg.L⁻¹ respectively.

Implications

While no trace metal contamination was detected, physicochemical parameters hinted at potential rancidity concerns. Pearson's correlation and principal component analysis identified poor storage and handling conditions as primary key factors to cooking oil spoilage.

Conclusions

The study recommends that regulatory bodies perform routine examinations to guarantee that commercially accessible vegetable oils satisfy the required quality and safety criteria. Furthermore, consumers should be educated on the importance of proper cooking oil storage and disposal.