Effects of Refining Processes on the Physicochemical Properties of Some Selected Vegetable Oils

Abstract

The post refining processes effects on the physicochemical properties of some selected vegetable oils were studied using standard analytical procedures. The results obtained showed that specific gravity were unaffected after refining with values 0.900 (crude and refined palm oil), 0.916 (crude and refined palm kernel oil), and 0.917 (crude and refined soybean oil). Refractive index was 0 for all the vegetable oils as well as melting points of palm kernel oil and soybean oil which remained unaffected post refining. Drastic colour reduction after refining was also noted as well as the melting point of palm oil which fell from 38°C to 21°C. Correspondingly, there was reduction in the chemical properties such as acid value (%FFA), peroxide value and saponification value. This study also revealed unsaponifiable matter showing no linear variation as it increased from 24.8% to 31.9% for crude and refined palm oil respectively and 25.05% to 33.15% for crude and refined soybean oil respectively with a decrease of 32.3% to 30.55% for crude and refined palm kernel oil respectively after refining. Hence, chemical properties are targeted and mostly affected in refining in a bid to getting an effective oil for human consumption while limiting the removal of nutritional content of the vegetable oil or fortification in cases of inadequacy.