PHYSICO-CHEMICAL QUALITIES OF RED PALM OIL AS AFFECTED BY MEDIA pH

Abstract

Water is an indispensable medium in food processing and the quality of water used in processing foods especially its pH can exert significant influence on the behaviour and properties of the food system. This work is an investigation on the effects of pH of water used in the processing of palm fruits on the physico-chemical qualities of the resulting oil. Palm fruits (Elaeis guineensis) were processed into edible red oil using water of different pH values (pH 3.5, 5.5, 7, 9.5, 11.5 and control). The resulting fresh oils were immediately subjected to physico-chemical analysis following standard procedures. The results showed that the pH of the oil samples ranged from 6.35-6.80; the iodine value of the samples ranged from 37.29mgI2/g-63.40mgI2/g; peroxide value ranged from 6.42mEq/kg/KOH-15.58mEq/kg/KOH; the specific gravity of the oil samples ranged from 0.91-0.93 while the saponification value of the oil samples ranged from 177.75mg/KOH/g - 236.36mg/KOH/g. The viscosity of the oil samples at (35oC) ranged from 134.45mPas- 205.04mPas and the free fatty acid ranged from 4.44%-6.84%; There were significant differences at P<0.05 for each of these physico-chemical qualities except in the specific gravity of the oil samples. Oil samples processed in acidic media (pH<7) were seen to have high viscosity and saponification properties whereas samples processed in alkaline media (pH> 7) were seen to be higher in iodine value but low in free fatty acid content and peroxide values. This work therefore reveals that the pH of water used in processing palm fruits can influence the physico-chemical qualities of the resulting palm oil. The quality of water especially its pH used in processing palm fruits should be identified as this work has revealed that media of both acidic and alkaline pH has both desirable effects and limitations in the quality of the resulting oil.