Copyright © 2019 IJAIR, All right reserved 133 International Journal of Agriculture Innovations and Research Volume 8, Issue 2, ISSN (Online) 2319-1473 Influence of pH-shifting Combined with Low- Frequency Ultrasound on Antioxidant Activity and Physicochemical Properties of Silver Carp Myofibrillar Protein Riya Liuhartana Nasyiruddin 1,2 , Amer Ali Mahdi 1,3 , Mohamed Ismael Ahmed 1,4 , Anwar Noman 1,5 , Qais Ali Al-Maqtari 1,3 , Qixing Jiang 1 , Yanshun Xu 1 and Wenshui Xia 1* 1 State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi, Jiangsu, 214122, China. 2 The Fishery Faculty, University of PGRI Palembang, Palembang, South Sumatera, 30263, Indonesia. 3 Department of Food Science and Technology, Faculty of Agriculture Sana’a University, Sana’a, Yemen. 4 Nyala Technical College, Sudan Technological University, P. O. Box 155, Sudan. 5 Department of Agricultural Engineering, Faculty of Agriculture, Sana’a University, Sana’a, Yemen. Abstract – This study aimed to investigate the effect of pH-shifting combined with low-frequency ultrasound on antioxidant and physicochemical properties of silver carp myofibrillar protein (MP). The antioxidant activity of the samples against DPPH ranged from 14.31% to 36.43%, and ABTS scavenging between 3.55 and to 22.56%. The ultrasonic treatment of the sample without changing the pH led to the best antioxidant activity against DPPH and ABTS. Protein solubility affected by treatments, which ranged from 30.11 to 88.26%, where the best solubility was at pH 8 with ultrasonic treatment which showed no significant difference to sample control. The turbidity increased in the treated samples at different pH levels without ultrasonic treatment, where the highest turbidity was 0.21 (A600) at pH 6 without ultrasound treatment, while the lowest turbidity was 0.03 (A600) at pH 12 with ultrasound. The highest water holding capacity of MP was achieved at pH 2 with ultrasonic treatment, which amounted to 7.83 g water/g MP. The results of this study indicate that the ultrasonic treatments of the samples at different pH significantly affected the antioxidant activities and physicochemical properties of MP obtained from silver carp. Keywords – Silver Carp, pH-shifting, Myofibrillar Protein, Ultrasonication, Antioxidant Activity, Physicochemical Properties. I. INTRODUCTION Silver carp (Hypophthalmichthys molitrix) is one of the prime and least expensive species of the freshwater fish commercially harvested in China because of its high nutritional value, rapid growth rate, high nutrition efficiency, as well as easy cultivation (Wang, Zhang, Mujumdar, & Mothibe, 2013). The content of cultured silver fish muscles of fat, crude protein, moisture are 2.52, 20.00 and 74.03%, respectively (Ashraf, Zafar, Rauf, Mehboob, & Qureshi, 2011). Silver carp is freshwater farmed fish rich in n-3 polyunsaturated fatty acids (PUFA) resembling marine fish sources (36% of total fatty acids) (Li, Sinclair, & Li, 2011). The Silver carp slices offer an attractive white color, but the fishy odor and the unpleasant earthy have limited consumers from accepting fish species widely (Wang et al., 2013). In the past years, there are products developed from silver carp, like surimi (Fu et al., 2012; H. Liu, Gao, Ren, & Zhao, 2014), fermented sausages (Xu, Xia, Yang, & Nie, 2010), and restructured fish (Wang et al., 2013). As the modern food industry develops, one ongoing challenge is looking for novel technologies to improve processing performance and minimize energy loss. In this regard, ultrasound as a novel green technology has been widely investigated in recent years (Xiong et al., 2016). Manuscript Processing Details (dd/mm/yyyy): Received: 10/09/2019 | Accepted on: 26/09/2019 | Published: 05/10/2019