Investigation of usage possibilities of gypsum plant (Gypsophila bicolor) saponins as natural emulsifiers in fish oil-astaxanthin microemulsions

In this thesis, it was primarily aimed to obtain astaxanthin, a compound with many functional properties, from shrimp waste and to make it soluble in water by dispersing it in fish oil, which is also a functional compound. For this purpose, the possibilities of using gypsum root saponins were investigated to create a completely natural emulsion system. In recent years, studies on saponin emulsions have been increasing in line with the increasing consumer demand for clean label and natural ingredient food systems. These studies have focused on the soap tree (Quillaja saponaria) on a global scale, and gypsum roots, which have similar characteristics in our country, are widely used in the Turkish delight and halva industry. In the scope of the thesis, astaxanthin was first extracted from red shrimp (Aristaeomorpha foliacea) processing waste. The resulting astaxanthin-loaded extract was diluted with fish oil (mackerel oil) to provide dispersion of astaxanthin in oil. Astaxanthin-fish oil mixture was emulsified with the help of Gypsophila bicolor root saponins (I), soy lecithin (II) and tween-80 (III). Ultrasonic assisted extraction technique has been applied in the extraction of gypsum root saponins, the extraction of astaxanthin and the formation of emulsions. Astaxanthin-fish oil emulsions, prepared using different natural and synthetic emulsifiers, were stored at room temperature (25±1ºC) and refrigerator temperature (4±1ºC) for 30 days. The rheological, physicochemical, and oxidative properties of the emulsions were compared on the 0th, 10th, 20th and 30th days of storage. Emulsion stability index, heat stability index, particle size, viscosity, turbidity and colour measurements, optical microscopy analysis, peroxide and antioxidant activity determination, fatty acid profile and astaxanthin concentration was determined. After grinding, the root crops were weighed 50 g, washed with n-hexane to remove their lipophilic compounds, and then subjected to ultrasonic assisted extraction with 500 ml of ethanol-water (70%-30%) mixture for 20 minutes. After undergoing various washing processes, the remaining sample was dissolved in 25 ml of methanol, 25 ml of ether was added, and the saponins were precipitated by centrifugation at 5500 rpm for 10 minutes. The samples were placed on blotting paper and kept in a desiccator for 1 night and then weighed. The amount of saponin in the gypsum roots was determined as 3.37±0.29 g/100 g dry sample. It was determined that the waste amount of shrimps used in the study as 57.59%±0.66%. The extract yield obtained from the wastes was found to be 17.0±0.8 g per 100 g dry matter. When the heat stability indices of the emulsions were examined, there was a difference between the emulsions starting from 70°C, and the heat stability of the tween-80 emulsion was found to be higher in the range of the tested values, while the lecithin emulsion was found to be the most sensitive to temperature. Considering the storage stability of the emulsions, it was determined that the emulsions were more stable in cold storage, as expected. The longer the storage time, the lower the emulsion stability. While tween-80 emulsion was more stable than other emulsions in room temperature storage, there was no statistically significant difference between tween-80 and saponin emulsions in refrigerator temperature storage. This may encourage the use of linseed root saponin as a natural emulsifier rather than a synthetic emulsifier, especially in food and pharmaceutical systems. According to the colour stability results of the emulsions, an increase in L* value due to fading and a decrease in a*, b* values were observed in the colour of the samples. It was determined that this decrease was higher in emulsions stored at room temperature. The turbidity values of the emulsions showed that there were statistically significant differences between the samples in day 0 data. Tween-80 emulsion was measured clearer compared to other emulsions and the turbidity value increased during storage. The turbidity value of the lecithin emulsion was measured the highest and this value gradually decreased during storage. During storage, the particle size of the emulsions increased, and accordingly, an increase in viscosity was observed. As with many emulsified systems, all emulsions in the study exhibited pseudoplastic flow, which decreased in viscosity with an increase in shear rate. When all the results were examined, it was concluded that the use of celandine root saponins in forming stable emulsions is promising.