Optimization of ultrasound-assisted bleaching process conditions of sunflower oil with different bleaching earth

Sunflower, one of the most important crops in the vegetable oil industry, holds a significant market share both globally and in our country. The crude sunflower oil obtained by extraction cannot be directly consumed due to its impurity content. Therefore, crude oils must undergo refining to remove impurities with minimal loss of bioactive components and oil. One of the most crucial stages in refining, the bleaching process, involves the removal of soap residues, phosphatides, pigments, and trace amounts of metals from the oil using adsorbents. In recent years, innovative methods have been introduced to enhance the bleaching process by optimizing parameters such as temperature and time in the conventional method. One of these methods, ultrasound technology, shortens the bleaching time and minimizes oil loss during the process. In this context, in the current thesis study, ultrasonic and conventional bleaching processes were performed using two different bleaching clays with distinct physicochemical properties (Madur CP 312 and Tonsil 210 FF) for the bleaching of sunflower oil. The study aimed to evaluate the effectiveness of different bleaching clays and the ultrasonic method. In the ultrasonic bleaching method, applied as an alternative to conventional bleaching, process conditions such as temperature (50°C and 90°C), process time (5-20 minutes), and bleaching clay amount (0.5-2.5 g/100 g oil) were determined through preliminary trials, and an experimental design was created using the Box-Behnken design. Free fatty acidity (FFA), peroxide value (PV), p-Anisidine and TOTOX values, along with the redness and yellowness color values, color removal rate (RGO), and oil yield (%) of the oil samples obtained from the ultrasound-assisted bleaching process were measured. For the optimization process conducted using the Response Surface Method (RSM), the response variables were defined as the redness color removal ratio (KRGO), yellowness color removal ratio (SRGO), oil yield (%), and total color removal ratio (RGO). The optimum values for bleaching clay amount (TM), ultrasound power (UG), bleaching time (US), and temperature (T) were determined. When ultrasonic and conventional bleaching methods were compared, the oil yields and KRGO, SRGO, and RGO values were significantly higher in ultrasound-assisted bleaching applications for samples bleached with both Madur CP 312 and Tonsil 210 FF (p≤0.05). KRGO values were 60% and 77.14% for Madur CP 312 and Tonsil OPT 210 FF oils bleached with ultrasound, respectively, whereas in the control group, they were 31.43% and 62.86%. The optimum process conditions for Madur CP 312 were determined as 2.4 g of bleaching clay, 60% ultrasound amplitude, 50°C temperature for 5.5 minutes. For Tonsil OPT 210 FF, the optimum conditions were 1.95 g of bleaching clay, 60% ultrasound amplitude, 50°C temperature for 13.35 minutes. In ultrasound-assisted bleaching, a 55.5% reduction in processing time was achieved for samples using Tonsil OPT 210 FF, and an 81.67% reduction was achieved for Madur CP 312 bleaching clay. Regarding bleaching temperature, the conventional temperature of 90°C was reduced to 50°C with ultrasound application, resulting in a 44.4% decrease in temperature. According to the thesis results, the ultrasound-assisted bleaching process improves the color of sunflower oil compared to the conventional method and reduces energy consumption by decreasing both process time and temperature. The application of environmentally friendly ultrasound technology in the bleaching of sunflower oil is expected to significantly enhance the industrial bleaching process. Keywords: Sunflower oil, bleaching, ultrasound, conventional, Box-Behnken, Response Surface Method.