Investigation of phenolic substance extraction from orange peel powder using ohmic heating process

In this thesis, total phenolic substance (TFS) was extracted from orange peel powder sample under different production conditions using ohmic heating assisted extraction (OHAE) method. In order to determine the maximum TFS extraction, maceration (MS) was applied and the yield of the total amount of phenolic substance obtained by the OHAE method was determined. The electrical and performance properties (energy, current, time, temperature) were determined and statistically investigated during the TFS extraction process from the orange peel sample using the OHAE process. The OHAE method was applied at 3 different solid: liquid ratios, 3 different voltage gradients (20, 25 and 30 V/cm), and 4 different temperatures (45, 60, 75 and 90˚C). OHAE system consists of power unit, test cell, microprocessor, connectors and computer. A linear increase in the temperature-time relationship from 20 °C to target extraction temperatures (45, 60, 75 and 90˚C) was found for all solid-liquid ratios and voltage gradients in the OHAE process. Process times increased with increasing target extraction temperature for all solid: liquid ratios and voltage gradients (p<0.05). The shortest processing time obtained at the solid to liquid ratio of 1:20, 90˚C and voltage gradient of 30 V/cm. It was determined that the target extraction temperature and voltage gradient had a positive effect on the heating time, but the solid: liquid ratio did not effect (p>0.05). In addition, it was determined that there was a linear increase in the current and temperature relationship between 20˚C and 90˚C, and the R² value was above 0.98. It was determined that the extraction temperature, voltage gradient and solid: liquid ratio had an effect on the total energy and average power values in the OHAE process. It has been determined that the amount of energy consumed decreases as the voltage gradient value increases (p<0.05). It was also found that the average power value increased with increasing extraction temperature for all solid: liquid ratios at the same voltage gradients (p<0.05). When the relationship of the OHAE process on the total phenolic substance content of the orange peel is examined; the highest TFM amount was found at 1:20 solid: liquid ratio and the lowest 1:60 solid: liquid ratio for all voltage gradient and extraction temperatures. When the change in the amount of TFM with the OHAE process using different production conditions was examined; statistically, it was determined that the solid: liquid ratio and the extraction temperature had an individual effect (p<0.05), but the voltage gradient had no effect (p>0.05). In the extraction process using the OHAE method, higher extraction efficiency was determined at 25 V/cm voltage gradient for all solid: liquid ratios (1:20, 1:40 and 1:60 g/ml). In addition, the highest extraction efficiency was achieved at 90˚C between four different temperatures (45, 60, 75 and 90˚C) for all other conditions. The highest extraction efficiency was obtained at the highest temperature value. As a result, it has been determined that the temperature is an important factor for obtaining TFM in the OHAE process, and both the applied voltage gradient and the applied temperature have a significant effect on the process time and performance values. In addition, the solid: liquid ratio is an important condition for the extraction process, so it is an important factor to be considered in the studies.