eng Science and Education Publishing Journal of Food and Nutrition Research 2333-1240 2020-01-24 8 1 50 57 10.12691/jfnr-8-1-7 JFNR2020817 article Shusheng Wang 1 2 Wenyi Fu 2 Hannah Han 3 Milan Rakita 4 Qingyou Han 4 Qin Xu xuq@purdue.edu 4 College of Life Science, Jilin Agricultural University, Changchun, China Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, USA School of Engineering Technology, Purdue University, W. Lafayette, USA Million tons of walnut shells, the waste by-product from walnut industries, are produced annually worldwide and are under-utilized in kernel manufacturing. Walnut shells are rich in phenolic compounds thus are valuable sources for antioxidants. In this study, the optimization of ultrasound-assisted extraction of phenolic compounds from walnut shells was performed with response surface methodology (RSM). The maximum yield of total phenolic compounds from walnut shells was 92.96±1.47 mg GAE/g DW under the optimum extracting conditions of 10 min at 0°C with 43.71% ethanol and 53.93% ultrasound amplitude. Analysis of antioxidant activities of the extracts found that the radical scavenging capacity of DPPH from the walnut shell extracts (10 - 500 ¦Ìg/mL) was 4.05 ¨C 88.59%, while the ferric reducing antioxidant power (FRAP) (10 - 100 ¦Ìg/mL) was 119.64-1278.95 ¦ÌM Trolox equivalent (TE). The results indicate that phenolic extracts from walnut shells are a good natural source of antioxidants, making this process a strong contender for future applications in the food and agricultural industries. http://pubs.sciepub.com/jfnr/8/1/7/jfnr-8-1-7.pdf walnut shell ultrasound-assisted extraction phenolic compounds antioxidant DPPH