Fotooksidasyon sırasında oluşan epoksi yağ asitlerinin incelenmesi

Lipid oxidation which adversely affects the human health, the quality and nutritional value of food products, also causes economic losses, occurs in series of reactions. Toxic products are formed during oxidation and make it a health issue. Lipid oxidation can be divided into categories such as photooxidation, autoxidation and thermoxidation depending on the factors triggering the oxidation including oxygen, heat, light and metal ion concentration. Photooxidation is one of the oxidation types which occurs in the presence of light and photosensitizers like chlorophyll and riboflavin. Photosensitizers cause the formation of singlet oxygen from ground state by energy transfer from light. Singlet oxygen leads to the formation of hydroperoxides from unsaturated fatty acids. In this study, photooxidation of three oil types (linseed, sunflower and olive oil) were investigated in the presence of chlorophyll. Fatty acid methyl esters (FAMEs) and epoxy fatty acid content of the oil samples were monitored by gas chromatograph with a flame ionization detector (GC-FID). Samples were kept under fluorescent light for two months. Virgin olive oil used as a chlorophyll source and its chlorophyll stripped counterpart (stripped virgin olive oil) were added to the samples to compare the oxidation levels. Primary oxidation products were also determined by peroxide value (PV), conjugated dienes (CD) and conjugated trienes (CT) analyses. Linseed oil samples had around 38% linolenic acid (C18:3) as the primary component, while sunflower oil samples had around 45% linoleic acid (C18:2). On the other hand, olive oil samples showed around 62% oleic acid (C18:1) as the primary component. Linseed oil samples were found to have the highest oxidation rate due to the high degree of unsaturation of linolenic acid. The amount of CD was higher than CT in all samples. Total epoxy fatty acid amount of all oil blends with chlorophyll were higher than oil blends without chlorophyll in the beginning of the incubation. Linseed oil blend with chlorophyll was found to have the highest amount of total epoxy (82.42µg g-1) in the beginning of the incubation. Sunflower oil blend with chlorophyll and olive oil blend with chlorophyll were determined as 62.97µg g-1 and 61.77µg g-1, respectively. In the end of incubation, linseed oil blend without chlorophyll was found to have the highest amount of total epoxy fatty acid (10866.28µg g-1) compared to the other oil blends. In the beginning of incubation, cis configuration was dominated in all oil blends with chlorophyll, but trans domination was seen in the oil blends without chlorophyll in the end of incubation.