Figure 2. Response surface plots (a–f) showing the effects of the extraction time, temperatures, amplitude, and concentration of solvent on the yields of the total phenolic content (TPC) from walnut shells

From

Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Walnut Shells and Characterization of Their Antioxidant Activities

Shusheng Wang, Wenyi Fu, Hannah Han, Milan Rakita, Qingyou Han, Qin Xu

Journal of Food and Nutrition Research. 2020, 8(1), 50-57 doi:10.12691/jfnr-8-1-7