Ultrasound assisted extraction of carotenoid and phenolic compounds from goji berry (Lycium barbarum L.) and optimization of extraction parameters

Goji berry is a fruit with high antioxidant activity due to the carotenoid and phenolic components. In this thesis, it is aimed to extract carotenoid and phenolic compound from goji berries by ultrasound-assisted method and to optimize the extraction parameters. For this purpose, first the ethanol concentration to be used in ultrasound-assisted extraction was determined and the extraction studies were carried out using 40% ethanol solution. During extraction, ethanol concentration (40%) and time (25 °C) were kept constant, ultrasound amplitude (25-75%), extraction time (2-6 min) and solvent:solid ratio (2:1-6:1 g/g) were chosen as independent variables. The effects of these variables on total carotenoid compound, zeaxanthin dipalmitate, total phenolic compound and total antioxidant activity in goji berries were investigated. Optimization studies were carried out with a Box-Behnken design consisting of a total of 17 trials with 3 factors and 3 levels, using the response surface method. According to the fit statistics results, it was determined that the most appropriate model for total carotenoid substance, zeaxanthin dipalmitate and total phenolic compound was the quadratic model, and the most appropriate model for total antioxidant activity was the 2FI model. The optimum condition for ultrasound-assisted extraction of goji berry was determined as 25% amplitude, 2 min time and 3.271:1 g/g solvent:solid ratio. Under optimum conditions, the response variables of total carotenoid substance, zeaxanthin dipalmitate, total phenolic substance and total antioxidant activity were estimated by the model as 300.12 mg/kg, 1052.17 mg/kg, 1353.95 mg/kg and 3.32 mM, respectively. Additionally, the effect of ultrasound-assisted extraction on the carotenoid and mineral profile of goji berry was examined. Ultrasound-assisted extraction did not show any adverse effects on the profile of carotenoid compound on a component basis. Zeaxanthin dipalmitate, β-carotene and zeaxanthin contents in goji berries were significantly increased by ultrasound-assisted extraction (p<0.05). Similarly, ultrasound-assisted extraction increased the amount of phosphorus, copper and selenium minerals in goji berry (p<0.05). The results of this study show that ultrasound-assisted extraction can improve the physicochemical quality of goji berry. It is thought that the obtained extracts can be used in the production of new functional foods and natural food additives with high added value.