M.A. Thesis:

Evaluation and comparison of physicochemical prooerties and fatty acid profile of sesameoil in thereways using ؛cold press and water axtraction

In term of importance of oils and its special position in diet in today's life and its impact on health, families tend to use unleaded natural oils such as crude sesame oil. Measurement of acidity and peroxide index in the shortest time after production and packaging, Indicates initial quality and oil production conditions. free fatty acids are an indicator for assessing the quality of the oil and its economic value. Edible oils( plant and animal), have a certain amount of free fatty acid, but may result in the release of free fatty acid from a specific and normal range due to spoilage factors and different reactions. Oxidation of lipids and oils lead to the formation peroxide and can cause various diseases. Accordingly, acidity and peroxide value determination are indicators of spoilage detection. Sustainability of liquid shoots against corrosion is always a problem and, on the other hand, the stability of the oils depends on the composition of their fatty acids. Sesame oil is of great importance due to the high levels of essential fatty acids, especially linoleic, from the nutritional point of view, and the presence of a high amount of this acid and, consequently, high non-greasy, makes the oil susceptible to oxidation. While the popularity of sesame oil is due to its oxidation resistance and the presence of antioxidant compounds. The purpose of this study was to investigate the extraction of sesame oil by using four extraction techniques, including: cold extraction, refined, traditional extraction and pressurized on its physicochemical properties, including acidity, peroxide index, antioxidant capacity, oxidative stability, acid fatty acid structure, Refractive index, Heavy metals and Anti-nutritional elements and was compared with Iran national Standard and finally, was the most suitable extraction for sesame oil. The acidity value of the traditional oil treatment, press stalls and cold extraction, in contrast to the sample of refined oil was exceed the standard limit value and the peroxide values of treatments of cold and refined extracted oil, in comparison with treatment of traditional and lubricated oils was standard limit. The evaluation of sesame oil samples by gas chromatography showed that polyunsaturated fatty acid linoleic (C18:2) and single monounsaturated fatty acid (C18:1) were the major two fatty acids. The results obtained from the oxidative stability of the analyzed oils indicate that the order of the stability of the samples from the fatty acid composition is the same as the stability of the samples in terms of the oxidative stability factor. The results of the DPPH test indicate that the order of the cold and refined extraction oil sample for the free radical inhibitory strength is similar in terms of the stability of the Rancimat test and the structure of the acidic acid, while the results of the two samples of traditional oil and Magazine press contrasts with the above mentioned. These results suggest that the most suitable method for extracting sesame oil based on acidity, peroxide and Refractive index was based on refined method and in relation to the three factor antioxidant capacity, oxidative stability, and acid fatty acid structure extraction method for cold extraction is the most desirable method. But since the cold extraction method is a laboratory and inaccessible method for the general public, the refined method is introduced as the best way to extract this valuable vegetable oil sample.

Keywords: Acidity, antioxidant capacity, extraction methods, fatty acid structure, gas chromatography, Oxidati