Food Hydrocolloids 102 (2020) 105612 Available online 19 December 2019 0268-005X/© 2019 Elsevier Ltd. All rights reserved. Infuence of phenolic compounds on physicochemical and functional properties of protein isolate from Cinnamomum camphora seed kernel Xianghui Yan a, b, c , Shibo Liang a, b, d , Ting Peng a, b, d , Guohua Zhang a, b, d , Zheling Zeng a, b, c, * , Ping Yu a, b, c, ** , Deming Gong b, c, e , Shuguang Deng b, c, f a State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047, China b Jiangxi Province Key Laboratory of Edible and Medicinal Resources Exploitation, Nanchang University, Nanchang, 330031, China c School of Resource and Environmental and Chemical Engineering, Nanchang University, Nanchang, 330031, China d School of Food Science and Technology, Nanchang University, Nanchang, 330031, China e New Zealand Institute of Natural Medicine Research, 8 Ha Crescent, Auckland, 2104, New Zealand f School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85284, USA A R T I C L E INFO Keywords: Cinnamomum camphora seed kernel Protein isolate Protein-phenolic complex Structure change Functional property ABSTRACT Cinnamomum camphora seeds are abundant in China. For high value utilization of Cinnamomum camphora seed kernel (CCSK) protein, the effects of phenolic compounds on physicochemical and functional properties of protein isolate (PI) from CCSK were investigated in this study. A total of 12 phenolic compounds in CCSK have, for the frst time, been tentatively identifed by HPLC-ESI-QTOF-MS 2 . PI had a higher level of protein content compared to that of protein-phenolic complex (PPC). The formation of PPC resulted in a reduction of free sulfhydryl groups content and surface hydrophobicity as well as an increase of particle size and zeta potential. Fourier-transform infrared spectroscopy showed that the contents of secondary structure of PI and PPC were not obviously different. However, a remarkable increase in β-sheet and a decrease in random coil of PPC compared to PI were found by circular dichroism. Differential scanning calorimetry analysis revealed that PPC was thermally more stable than that of PI. PI and PPC exhibited superior essential amino acid composition and similar protein subunits. Furthermore, PPC exhibited higher solubility, better foaming and emulsifying properties than those of PI. These results suggested that the protein products from CCSK may be used as natural functional materials in the food industry. 1. Introduction Cinnamomum camphora seeds are abundant in China, with an annual yield of more than 1 million tons. People from south of the Yangtze river in China have been consuming Cinnamomum camphora seed kernel (CCSK) like soybean and peanut since 1960s. CCSK is rich in medium- chain oil and protein, with the contents of 48.24–62.60% and 17.15–26.33%, respectively. Since 2009, we have studied the extraction technology, structure and physiological effects of Cinnamomum cam- phora seed kernel oil (CCSKO), and found that CCSKO, the only natural medium-chain oil discovered in the world, improved the lipid and glucose metabolism disorder in SD rats (Fu et al., 2015, 2016b; Fu, Zeng, Zeng, Wang, & Gong, 2016a). However, to our knowledge, there are no studies on the isolation, structure and biological activity of CCSK protein. With the increasing interest on renewable and sustainable protein resource of plant origin (Rodrigues, Coelho, & Carvalho, 2012), the protein products isolated from CCSK are expected to be applied to food industry by studying their physicochemical and functional properties. The traditional alkaline-solution and acid-precipitation technique is typically used to isolate proteins from plants, but the technique also facilitates the extraction of phenolic compounds (Hernandez-Jabalera et al., 2015). In this procedure, a portion of phenolic compounds may bind with proteins through covalent bond in the presence of oxygen (Kroll, Rawel, & Rohn, 2003). Specifcally, these highly reactive phenolic compounds could covalently combine with sulfhydryl (-SH) and amino (-NH 2 ) groups of proteins at high pH values (Pierpoint, 1969). Studies have shown that individual phenolic compounds, such as * Corresponding author. State Key Laboratory of Food Science and Technology, Nanchang University, 235 Nanjing East Road, Nanchang, 330047, China. ** Corresponding author. State Key Laboratory of Food Science and Technology, Nanchang University, 235 Nanjing East Road, Nanchang, 330047, China. E-mail addresses: zlzengjx@hotmail.com, zlzengjx@163.com (Z. Zeng), cpu_yuping@126.com (P. Yu). Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: http://www.elsevier.com/locate/foodhyd https://doi.org/10.1016/j.foodhyd.2019.105612 Received 25 August 2019; Received in revised form 19 November 2019; Accepted 18 December 2019