| Popis: |
V svoji diplomski nalogi sem raziskovala termično stabilnost nekaterih jedilnih olj, in sicer olivnega in koruznega olja ter olja oljne ogrščice. Olja so estri glicerola in višjih maščobnih kislin in spadajo v podskupino lipidov, kar pomeni, da so slabo oz. popolnoma netopni v vodi. Termična analiza je veja znanosti o materialih, kjer se njihove lastnosti preučujejo v odvisnosti od temperature. Pri temperaturah nad 180 °C, ki jo dosežemo pri pripravi hrane, lahko določena olja že začnejo termično razpadati, kar bi z zdravstvenega vidika radi preprečili, saj so razpadni produkti zdravju škodljivi. Predvsem je to pomembno pri cvrtju, saj olje ponavadi uporabimo večkrat zaporedoma. Z nekaterimi najpogosteje uporabljenimi tehnikami termične analize (termogravimetrijo, diferenčno termično analizo in diferenčno dinamično kalorimetrijo) lahko določimo začetno temperaturo termičnega razpada raznovrstnih olj, preučujemo primernost antioksidantov za dodajanje oljem, ki jih termično obdelujemo, ter zaznavamo spremembe, ki so posledica avtooksidacije med dolgotrajnim hranjenjem ali pa toplotne oksidacije. Vse omenjene uporabe teh metod so prikazane v pričujočem diplomskem delu. In my diploma thesis the thermal stability of some edible oils, namely olive oil, corn oil and canola oil, was investigated. Oils are esters of glycerol in higher fatty acids and belong to the subgroup of lipids which means that they are partially or completely insoluble in water. Thermal analysis is a branch in material science where material properties are investigated in relation to temperature. At temperatures above 180 ° C, which are reached during food preparation, oils can thermally decompose. This must be prevented for health reasons, as the decomposition products are harmful to health. This is particularly important in case of frying, as the same oil can be used several times. With some of the most frequently used thermoanalytical methods (thermogravimetry, differential thermal analysis in differential scanning calorimetry) the onset temperature of the thermal decomposition of oils can be determined. Potential antioxidants added to thermally treated oils, and changes resulting from auto-oxidation processes during the long shelf life or caused by thermal oxidation can also be investigated using the above techniques. All mentioned applications of these methods are shown in this diploma thesis. |
