Optimization of Ultrasonic Extraction Parameters for Polyphenolic-Rich Extract from Peanut Shells and Its Application in Functional Yogurt

The aim of this study was to optimize the parameters of ultrasonic extraction of polyphenolic compounds from peanut shells and to evaluate the feasibility of using the obtained extract in the development of functional yogurt. The extraction factors considered were the ethanol concentration, particle size of peanut shells, and extraction time. Process optimization was performed using response surface methodology based on a second-order central composite design. Extraction yield and total polyphenol content were selected as the optimization criteria. The optimal ultrasonic extraction conditions were determined as an ethanol concentration of approximately 70% ethanol, 300 μm particle size, and 53 min. Under these conditions, the predicted extraction yield was 9.05% and the total polyphenol content reached 95.15 mg GAE/g of dry extract. The extract obtained under the optimal conditions was used to fortify yogurt at concentrations of 0.25%, 0.5%, and 0.75%. Physicochemical analysis showed that the addition of peanut shell polyphenol extract increased the water-holding capacity and reduced syneresis of yogurt during storage compared with the control sample. Changes in pH and titratable acidity remained within the typical ranges for fermented dairy products. The results confirm the potential of peanut shells as a promising source of polyphenolic compounds and demonstrate the feasibility of using the optimized extract in the development of functional fermented dairy products.