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V magistrski nalogi sem raziskovala termično in oksidativno stabilnost različnih ekstra deviških oljčnih olj ter prisotnost antioksidantov, stopnjo nenasičenosti maščobnih kislin in vsebnost prostih maščobnih kislin v teh oljih. Olja so v glavnem sestavljena iz triacilglicerolov, ki so estri glicerola in treh maščobnih kislin. Od celotne kemijske sestave so odvisne lastnosti olja. Termično stabilnost sem proučevala med segrevanjem v pretoku zraka oziroma dušika, meritve sem izvajala na simultanem TGA/DSC instrumentu. Čas inducirane oksidacije (OIT) pri 160 °C je bil določen z DSC meritvijo. Določila sem še jodovo število (IV), ki je merilo za stopnjo nenasičenosti olja in predstavlja maso joda v gramih, ki se veže na 100 g olja. Določila sem tudi kislinsko število (KŠ), ki je merilo vsebnosti prostih maščobnih kislin in predstavlja maso KOH v miligramih, ki se veže na 1 g olja. Na enak način sem določila še kislost, ki pa predstavlja % vsebovane proste oleinske kisline. Pripravila sem tudi več preprostih eksperimentov, ki so primerni za izvedbo v srednji šoli, s katerimi lahko kvantitativno in kvalitativno določimo prisotnost antioksidantov in nenasičenost. In my master's thesis, the thermal and oxidative stability of various extra virgin olive oil samples as well as the presence of antioxidants, the degree of unsaturation of fatty acids and the content of free fatty acids in these oils, were studied. The oils are composed mainly of triacylglycerols, which are esters of glycerol and three fatty acids. The overall chemical composition determines the properties of the oil. Thermal stability was studied while heating the oil sample in air or nitrogen atmosphere using a simultaneous TGA/DSC instrument. The oxidation induction time (OIT) at 160 °C was determined by DSC measurements. The iodine number (IV), which is a measure of the degree of unsaturation of the oil and represents the mass of iodine in grams that binds per 100 g of oil, was determined. The acid number, which is a measure of the free fatty acid content and represents the mass of KOH in milligrams that binds 1 g of oil, was also determined, as was the acidity, which indicates the percentage of free oleic acid contained. A series of simple experiments to determine quantitatively and qualitatively the presence of antioxidants and unsaturation, suitable for use in secondary education, were also developed. |
