Effect of Bleaching on the Physico-chemical Properties of Two Selected Vegetable Oils Using Locally Sourced Materials as Adsorbent

The quality and stability of palm kernel oil (PKO) and cottonseed oil (CTSO) as affected by bleaching using modified oyster shell powder (OSP) and periwinkle shell powder (PSP) were evaluated by analysing their physicochemical properties. The two adsorbents potential was improved on by modification using 5 M HCl and H2SO4. The determinations of the parameters were carried out by titration, while the refractive index was determined using a refractometer. The results indicate that the saponification values (SV) of PKO and CTSO increase after bleaching. However, the result further shows that the peroxide values (PV) of bleached PKO using OSP and PSP modified with 5 M HCl decreased (17.49±0.01 and 20.04±0.08 respectively) and also the iodine values decreased (3.15±0.13 and 3.41±0.02 respectively).

The same decrease in PV and IV values is observed in PKO bleached using 5 M H2SO4. The values of PV for OSP and PSP are 4.99±0.005 and 12.77±0.77 respectively while the IV values for OSP and PSP are1.85±0.01 and 12.53±0.09 respectively. Also, 5 M HCl and H2SO4 modified OSP and PSP reduced the IV content in CTSO. (5 M HCl OSP and PSP are; 3.15±0.13 and 3.41±0.02 respectively while 5 M H2SO4 OSP and PSP values are; 3.33±0.04 and 3.13±0.06 respectively). The study revealed that the bleaching through the use of OSP and PSP influenced the components and properties of the PKO and CTSO, improved on their qualities and therefore, the adsorbents can serve as alternatives to the costly adsorbents available in the markets.