Microwave-Assisted Phytochemical Extraction from Walnut Hull and Process Optimization Using Box-Behnken Design (BBD)

The walnut green hull is an agro-waste, a source of natural dye and volatile compounds with various biological activities, but the main challenge with the conventional extraction method is the quality and quantity of the volatile compound (dye) extraction from walnut hull waste. The objective of this research work is to use microwave-assisted extraction (MAE) as an emerging technology. Further, the MAE process was optimized using a Box-Behnken Design (BBD) of response surface methodology (RSM). The variables in MAE process optimization were microwave power, microwave time, solvent volume, and raw material particle size. The result indicated that MAE produces a higher extraction yield compared to the conventional method. The RSM analyses showed an increase in extract yield, total phenolic content, and total flavonoid content, along with antioxidant activity. The optimized condition parameters of MAE were reported to be 363.64-watt microwave power, 3.133 min, 39.999 mL/g solvent volume, and 150 mu m particle size, the extract yield was 39.65%, followed by total phenol content of 83.535 mgGAE/g, and total flavonoid content was 18.98 mgQAE/g, while antioxidant activity was 76.298%. Additionally, the optimized sample was characterized using SEM and GC-MS.