| Abstract: | A detailed study has been performed of the changes made by the action of the independent variables (temperature, flow of stripping gas, thickness of oil layer in the deodorizer, and length of the process) on different quality parameters of olive oil deodorized and/or physically refined in a discontinuous process (in a pilot plant of 250 kg maximum capacity using nitrogen as stripping gas in place of steam). The changes caused in the contents of unsaturated fatty acids (elaidinization) in the contents of 3,5-stigmastadiene (dehydrated beta sitosterol), and of saturated fatty acids in the β-position have been studied. A bleached olive oil with 1.85% of ffa was analyzed in a design of experiments using a modified Yates factorial statistical analysis. The results obtained from similar assays carried out with bleached sunflower seed oil with 0.56°C of acidity (using a 4 × 4 latin square experimental scheme) were used as starting point to select the most important independent variables. It has been concluded that the content of trans fatty acids in the deodorized oils depends indirectly on the four variables, and although the elaidic acid content is correct in all cases, the content of trans 18:2 and trans 18:3 readily exceeds the permitted limit when the temperature is above 250°C and the residence times are long. The same occurs with the content of saturated fatty acids in β-position of triglycerides and the content of 3,5-stigmastadiene. This means that the oil must be deodorized at a lower temperature, with longer residence time and greater energy spending. As the different olive oils have different initial characteristics, it is of interest to establish criteria, which are able to forecast whether a particular oil could be refined under pre-set conditions. A similar study should be made to obtain refined oils in other plants. |
