Investigations on processing and preservation of fish oil by emulsion and encapsulation techniques

This study consists of three main sections. The first section investigated which emulsion method could produce a more durable and efficient fish oil emulsion. For this purpose, multiple emulsions were produced from olive oil using three different methods: single-step, two-step and membrane methods, and the resulting emulsions were compared in terms of droplet size and zeta potential. Although similar droplet size and zeta potential values were achieved both in single-step and membrane methods, single-step method was further studied for optimization of the emulsion conditions due to ease of application and convenience. Optimum emulsion conditions were determined and under these conditions, fish oil and olive oil emulsions were produced for evaluation according to pH, acidity, conductivity, viscosity, color, zeta potential, droplet size, polydispersity index, creaming index, emulsion yield, in-vitro digestion, FTIR and microscopic visuals. In the second section of the study, it was investigated which wall material and drying method could be used to coat fish oil emulsions effectively. For this purpose, multiple emulsions were produced under optimum conditions and these emulsions were encapsulated both by spray and freeze drying using gelatin, whey protein and soy protein as wall materials. Spray and freeze drying were compared in terms of encapsulation yield and encapsulation efficiency. It was determined that freeze drying was more successful in terms of yield and encapsulation efficiency. Then, an optimization study was carried out to determine optimum conditions for encapsulation based on freeze-drying separately for each protein used as wall material. Fish oil capsules produced under optimum encapsulation conditions were compared according to yield, efficiency and Hausner ratio, and whey protein gave the best results. In addition, olive and fish oil capsules were produced under optimum conditions with whey protein. After that; encapsulation yield and efficiency, amount of surface oil, wettability, solubility, bulk and compressed density, Hausner ratio, Carr index, amount of dry matter, color, in-vitro digestion analyses were carried out for a through evaluation of the capsules obtained. In the last section of the study, product quality and oxidation process were monitored by storing raw fish oil, single emulsion of fish oil, multiple emulsion of fish oil and encapsulated fish oil emulsions produced with whey protein at two different temperatures (25 and 60°C). During storage, free fatty acid content, peroxide value, thiobarbituric acid (TBA) amount, p-anisidine value, and conjugated diene-triene analyzes were carried out for a comparative evaluation of the emulsion and encapsulation processes for preservation of fish oil quality. The total of 27 experimental run were carried out for optimization study of the emulsion process. The droplet size of the emulsions varied between 126-897 nm and the polydispersity index varied between 0.128-0.518. The pH value of olive oil emulsion produced under optimum conditions was 2.89±0.01, and that of fish oil emulsion was 2.80±0.01. The conductivity values of olive oil and fish oil emulsions were 9.65±0.05 and 9.82±0.11 mS/cm, respectively. The viscosity value was 2.50±0.00 and 3.75±0.00 cP in the same samples, respectively. The zeta potential values of these samples were determined as -50.70±1.70 and -48.56±1.06 mV, and the creaming index values were determined as 8.02±0.66% and 13.58±0.54, respectively. For selection of the drying method for encapsulation, freeze drying and spray drying at three different temperatures, i.e. 140, 160, 180 °C, were studied. The capsules obtained were compared in terms of yield and encapsulation efficiency. In gelatin capsules obtained by spray drying, both yield and efficiency increased as the temperature of spray drying increased, but the highest yield was obtained by freeze drying and the highest efficiency was obtained by spray drying at 180°C. In whey protein capsules, a decrease in efficiency was observed as the temperature increased in spray drying, and the highest yield and efficiency results were obtained by freeze drying. In soy protein, the efficiency decreased while the yield values did not change much as the temperature increased. The highest yield and efficiency results were obtained with soy protein and freeze drying at the end. As a result, the optimization study was carried out based on freeze drying. In the optimization study conducted with three different proteins, the highest efficiency, solubility and Hausner ratio values were obtained in whey protein capsules. Then, capsules were obtained by using whey protein and olive and fish oil emulsions; and yield, surface oil amount, activity, wettability, solubility, bulk and compressed density, Hausner ratio, Carr index, dry matter, color, in-vitro digestion, TGA, DSC, FTIR analyzes were carried out. Encapsulation efficiency in olive and fish oil capsules was found to be 98.61±0.23% and 98.22±0.07%, respectively. Wettability of the oil capsules was 16.51±0.37 and 20.70±0.41 s. Solubility rate was 44.17±0.43 and 46.06±0.58% for the same samples. In both capsules, Hausner ratio was 1.32 and Carr index was 23.81. Dry matter content of the capsules was high and 98.97±0.11% for olive oil capsules and 99.03±0.05% for fish oil capsules. When the color values of the capsules were examined, it was seen that L*, a*, b* and whiteness index values of the fish oil capsules were higher compared to those of olive oil capsules. Peroxide value was 26.13 meq O2/kg oil at the 48th hour of storage in fish oil samples stored at 60°C, 22.17 meq O2/kg oil in fish oil samples emulsified with single step method, and 21.07 meq O2/kg oil at the 72nd hour in fish oil samples emulsified with multiple emulsion method and then decreased in the later stages of the storage. Peroxide value of fish oil capsules showed a steady increase and reached the highest level of 11.66 meq O2/kg oil at 60°C and 96th hour of the storage. During storage at 25°C, peroxide values increased steadily and the highest values were obtained in raw fish oil. A similar situation was also observed in the conjugated diene results. An increase was observed in TBA values in all samples. The highest TBA value was 22.26 MDA/kg oil for raw fish oil, 15.70 MDA/kg oil for single step emulsion, 13.04 MDA/kg oil for multiple emulsion, and 8.46 MDA/kg oil for fish oil capsule. A similar situation was observed in p-anisidine and conjugated triene results. In conclusion, emulsion and encapsulation led to longer oxidative stability of fish oil quality and multiple emulsion protected fish oil better compared to single step emulsion. Keywords: Freeze drying, Fish oil, Multiple emulsion, Spray drying, Whey protein