Changes in olive oil components during deodorization and/or physical refining at the pilot plant scale using nitrogen as stripping gas

A detailed study has been performed of the changes made by the action of th e independent variables (temperature, flow of stripping gas, thick ness of oil layer in the deodorizer, and length of the process) on differ ent quali ty parameters of olive oil deodorized and/or physically refined in a discon tinuous 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-stigmastad iene (dehydrated beta sitosterol), and of saturated fatty acids in the beta -position have been studied. A bleached olive oil with 1.85% of ffa was ana lyzed in a design of experiments using a modified Yates factorial statistic al analysis. The results obtained From similar assays carried out with blea ched sunflower seed oil with 0.56 degrees of acidity (using a 4 x 4 latin s quare experimental scheme) were used as starting point to select the most i mportant independent variables. It has been concluded that the content of t rans fatty acids in the deodorized oils depends indirectly on the four vari ables, and although the elaidic acid content is correct in all cases, the c ontent of trans 18:2 and trans 18:3 readily exceeds the permitted limit whe n the temperature is above 250 degrees C and the residence times are long. The same occurs with the content of saturated fatty acids in beta-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 ini tial characteristics. it is of interest to establish criteria. which are ab le to forecast whether a particular oil could be refined under pre-set cond itions, A similar study should be made to obtain refined oils in other plan ts.