Effects of high temperatures and duration of heating on olive oil properties for food use and biodiesel production

Heating deteriorates the physicochemical propertiesof a vegetable oil for both edible and biofuel uses. Theparameters for edible olive oil are established by European Union regulations and by the International Olive Council.The properties of a vegetable oil to be used as a sourcefor biodiesel production are indicated by the German DIN51605 for rapeseed oil. Biofuel properties are described by the European EN 14214 and the North American ASTM 6751 standards for biodiesel. It is useful to know how temperatureand heating duration influence the physicochemicalproperties of olive oil. Free acidity, refractive indexand myristic acid were not significantly influenced by temperature and heating duration. K232, K266, K270, K274, p-anisidine value, totox index, kinematic viscosity (at 30,40, 50 °C), estimated higher heating value, relative density,and cetane number increased during olive oil heating.The biological properties: iodine value, oxidative stability index, antiradical (2,2-diphenyl-1-picrylhydrazyl radical,DPPH∙) activity, and phenol content, decreased when time and temperature increased. Fatty acid methyl esters were highly influenced by the applied variables. Almost all the fatty acid methyl esters, except myristic, stearic, and arachidic acid esters, were influenced by the combined effect of temperature and time in a very highly significant level.These results show how temperature and duration of heating influence extra virgin olive oil degradation for both edible use and biodiesel production.