Susam tohumuna uygulanan ön işlemlerin kalite özellikleri ve yağ verimine etkisi

In the last 30 years, vegetable oil especially the pressed oil consumption increased because of effects on human health. They have high amount of beneficial compounds such as antioxidants, essential oils, minerals, and vitamins. However, in order to produce the amount of consumers' demand, industry has been applying refining for years. This situation causes decrease in bioactive compounds present in vegetable oils. Nowadays, popular oilseed production method is pressing without refining process. These oils are generally defined as "cold-pressed oils, virgin oils or unrefined oils". Indeed, there is a misundersting about these terms between consumers. Virgin oil does not mean cold-pressed oil, and vice versa. Cold-pressed oils are vegetable oils obtained without altering the nature of the oil, by mechanical procedures such as expelling or pressing. They may have been purified by washing with water, settling, filtering and centrifuging only. Therefore, they maintain their beneficial compounds. Heat treatments are used to increase high oil yield in industrial applications. Roasting and microwave treatments are the most popular methods applied as pre-treatments. On the other hand, there becomes a risk in loosing beneficial compounds present in the seeds. Therefore, it is needed to solve the problems in both heat treatments. Ultrasonic treatments have emerged in the last few years that are used to increase oil yield with GRAS solvents. In this method, solvent behaves like heat to disrupt cell walls of seeds and so oil is produced. Research studies were performed for increasing oil yield and quality of vegetable oils such as soybean, sunflower, olive oil, and rapeseed. Apart from these seeds, there are many types of other seeds that have high oil and high bioactive content such as hazelnuts and sesame seeds. Sesame seeds have magical beneficial compounds but unfortunately World doesn't perfectly know about them yet. They have high amount of oil, protein, antioxidants, phenolic compounds, minerals and etc. Sesame seeds themselves, oil, cake, and hulls have separately these magical compounds. There is lack of information about how sesame oil can be obtained in high yield without loosing quality. Therefore, in this thesis, Turkish type sesame seeds were treated by different pretreatments to have high oil yield and quality characteristics. In the experimental studies, three treatments were chosen which were conventional treatment (roasting), microwave treatment (MWT), and ultrasonic assisted ethanolic (UAE) treatment. Each treatment was applied before hydraulic pressing and obtained press oil and sesame cake were analysed for various parameters. In the experimental studies, firstly, the quality characteristics of sesame seeds were determined before pretreatments and pressing. Moisture content, refractive index, ash content, oil content, protein content, fatty acid composition, free fatty acid content, peroxide value, and oxidation stabilities were analysed and compared for control samples and treatments. In the next steps, sesame seeds were roasted, treated with microwave, and treated with ultrasound. For each treatment, oil yield and quality characteristics were determined. In experiments, following effects were searched: for roasting; duration, temperature, and starting moisture content, for microwave treatment; energy power level and duration, for ultrasonic treatment; alcohol-water concentration, solid/liquid content, duration, and amplitude. Findings that are obtained from this experiment can be summarized as follows: According to the results, moisture content was decreased from 5.1±0.03% to 2.2±0.05% by 165 °C roasting and 0.9±0.002% by 220 °C roasting. By applying microwave treatment with different depth and power level, moisture content was decreased by 1.5-3.5%. High power level at 1 cm depth provided the best result in 1.2% moisture content. Ultrasonic treatments didn't have effect on moisture content as much as heat treatments. But moisture content was decreased by 1.0-1.5%. Refractive index for non-treated and treated samples didn't change in a great deal. Therefore, ultrasonic effect wasn't studied. Free fatty acid (FFA) content increased from 2.5±0.26% to maximum 6.3±0.1% in sesame cake oil and 15.7±1.21% in press oil by roasting, 11.6±0.55% in sesame cake oil and 6.7±0.26% in press oil by microwave treatment, 15.8±0.52% in sesame cake oil and 8.0±0.32% in press oil by ultrasonic treatment. When the results were compared, it was clearly seen that treatments didn't decrease FFA content. When treatments were compared with each other, high level microwave in non-grinded samples and 210°C roasting in non-grinded samples can be acceptable for having low FFA content. Oil content of sesame seeds were determined by Soxhlet extraction. According to the results, oil content increased from 48.7±3.18% to maximum 56.6±3.55% by 210 °C roasting in grinded seeds, 63.3±3.12% by medium power level of microwave at 1 cm depth, and 62.5±2.20% by solid/liquid:1/10 ultrasonic treatment. High oil content was obtained at by medium power level of microwave treatment and by solid/liquid:1/10 ultrasonic treatment. Peroxide value (PV) increased from 3.4±0.27 meq/kg oil to 10.0±0.10 meq/kg oil after ultrasonic treatment during 20 days of storage. After 20 days of storage, PV of raw sesame seeds decreased from 9.2±0.59 meq/kg oil to 7.7±0.56 meq/kg oil after 165°C roasting, 4.6±0.54 meq/kg oil after high level microwave treatment. For 30 days of torage, results were similar to that of 20 days storage. Again high level microwave and 165°C roasting gave us low PV meaning that we can obtain longer shelflife for sesame oil. Maximum total phenolic content (TPC) of sesame seeds, sesame oil, and sesame cake were found as 63.7±3.00, 108.9±5.47, and 185.3±10.14 mg gallic acid/mL for 210°C roasted samples, high level microwave treated samples, respectively. Ultrasonic treatment couldn't be effective for obtaining high amount of TPC. In contrast, AOX results showed that ultrasonic treatment was effective as heat treatments. However, three power level microwave treatments were the most effective for obtaining high antioxidant activity. In NMR analysis, T2 (relaxation time) Carr-Purcell-Meiboom-Gill (CPMG) experiments were conducted for oils which were obtained in MWT, UAET, and roasting treatments. For T2-CPMG experiments, there was no significant difference found between the T2 values and relative areas of each compartment for MWT and roasting treatments. This result was expected, as exchange times are very slow in the absence of gradients. For UAET, that is a homogenization technique, the number of peaks decreased to three after the treatments. T2 values of the peaks were not different from the microwave and high temperature ones. At 90% amplitude for the 96% EtOH samples, sonication time was doubled and resulted a decrease in the T2 values. This showed that ethanol interacted with oil more at higher sonication times. Oxidation stability was determined by Rancimat method. According to the results, induction time was longer in 210 °C roasting and high MWT when it was compared to non-treated one. Ultrasound treatment was not effective as roasting and MWT. Induction time was recorded as 14.9±1.56 h for non-treated sesame oil, 14.5±0.55 h for 210 ̊C roasted sesame oil, 13.53±1.85 h for high MWT, 11.85±0.73 h for medium MWT, and 11.55±1.10 h for 90% amplitude UAET. Looking at the TPC and TEAC results, oxidation stability went through in the same order. Therefore, higher oxidation stability values of sesame oil could be attributed to higher antioxidants (lignans) together with tocopherol.. The first aim of this study was to find oil yield after treatments. Oil yield was found in both grinded and non-grinded sesame seeds. Oil yield was calculated bu applying mass balance by taking into consideration of press oil and sesame cake oil. In grinded sesame seeds, oil yield increased from 38.8% to 56.0%, 68.8%, 70.0%, and 63.8% by roastings, medium level at 1 cm depth, high level at 1 cm depth, and ultrasonic treatment with 96% ethanol concentration, respectively. As it was concluded that each treatment had effects on oil yield and quality characteristics of sesame oil. But it is clearly seen that microwave treatment and roasting gave the best results. For ultrasonic treatment, ethanol concentration, time, amplitude, and solid/liquid were important and showed different results to compare in itself. However, when it was compared with heat treatments, more study is needed. In industrial scale, medium/high level of microwave or roasting can be used to have high oil yield with high functional properties and oil quality for sesame seeds.