the effect of bleaching process on the physical and chemical characteristics of canola and sunflower seed oils

bleaching process is an essential stage in the refining of vegetable oils and fats. in this process the colour and the primary and secondary oxidation products are removed by the treatment with the acid activated bleaching earth .the aim of this project is to understand the effect of bleaching on the physical characteristics and chemical constituents of neutralized canola and sunflower seed oils. canola and sunflower seed oils were bleached at 100o c for 30 minutes. the results indicated that there were significant reductions in peroxides and red and yellow colours of the oils. the induction period representing the oil resistance to oxidation was improved however the acidity was increased that might be due to the nature of the acid activated earth that has caused slight hydrolysis. slight changes in fatty acid composition was observed that was due to the oxidation of poly unsaturated fatty acids namely linoleic acid in both oils. some reduction in the total non saponifiable matter was observed. this might be due to the oxidation of tocopherols and changes of the sterols structures due to their conversion to steroidal hydrocarbons.