Effects of process parameters on 3‑MCPD and glycidyl ester formation during steam distillation of olive oil and olive pomace oil

The objective of refining, which is applied to vegetable oils, is to remove or reduce undesired substances and impurities in crude oils. Oil refining is applied by chemical or physical means. Chemical refining consists of degumming, alkali neutralization, bleaching and deodorization operations. In physical refining, degummed and bleached oils are subjected to steam distillation; where neutralization and deodorization steps are carried out in same operation as a last step. Elevated temperature might yield in undesired side reactions and formation of process contaminants such as 3-monochloropropane 1,2 diol (3-MCPD) and glycidyl esters, which are known as toxic contaminants during steam distillation process. The aim of this study is to determine the effects of process parameters (temperature, pressure and water flow rate) on formation of bound 3-MCPD and glycidyl esters during steam distillation of olive oil and olive pomace oil. Besides; optimization of these process parameters to minimize the bound 3-MCPD and glycidyl ester formation stands to be as another goal of this study. For this purpose; bleached olive oil and deacidified/bleached olive pomace oil were obtained from a local refining plant. Bleached oils are analyzed to determine basic chemical characteristics and bound 3-MCPD and glycidyl esters contents. Results showed that bound 3-MCPD and glycidyl esters were not detected in olive oil; whereas bleached pomace oil contained 4,1mg/kg bound 3-MCPD and 0,3mg/kg glycidyl esters; initially. Steam distillation operations were carried out in a laboratory scale steam distillation equipment in which process temperature, pressure and water flow rate of stripping steam were adjustable. Experiment sets were designed by using Box-Behnken methodology. Bound 3-MCPD and glycidyl esters contents were chosen as responses of experimental design. The effect of steam distillation process parameters on bound 3-MCPD and glycidyl esters formation were determined by using Design-Expert software. Process parameters were optimized using Response Surface Methodology to minimize the bound 3-MCPD and glycidyl esters formation. It was concluded that, temperature was significantly effective on bound 3-MCPD and glycidyl esters formation in olive oil and bound 3-MCPD formation in olive pomace oil during steam distillation (P<0,05). Pressure and water flow rate were found to be ineffective (P>0,05) on formation of bound 3-MCPD and glycidyl esters for steam distillation of both oils. Optimum steam distillation parameters were determined as 230ºC temperature, 4 mbar pressure and 1,2ml/min water flow rate to achieve minimum bound 3-MCPD and glycidyl esters formation for olive oil. Optimum steam distillation parameters for olive pomace oil were predicted as 230ºC temperature, 2 mbar pressure and 1 ml/min water flow rate.