Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Walnut Protein Isolate
Fei Zhao,
Xiaosong Zhai,
Xuemei Liu,
Meng Lian,
Guoting Liang,
Jingxiang Cui,
Haizhou Dong,
Wentao Wang
Affiliations
Fei Zhao
College of Agronomy and Environment, Shandong Facility Horticulture Bioengineering Research Center, Weifang University of Science and Technology, Weifang 262700, China
Xiaosong Zhai
College of Food Science and Engineering, Engineering and Technology Center for Grain Processing of Shandong Province, Shandong Agricultural University, Taian 271018, China
Xuemei Liu
Jinan Fruit Research Institute, All-China Federation of Supply and Marketing Co-Operatives, Jinan 250014, China
Meng Lian
College of Agronomy and Environment, Shandong Facility Horticulture Bioengineering Research Center, Weifang University of Science and Technology, Weifang 262700, China
Guoting Liang
College of Agronomy and Environment, Shandong Facility Horticulture Bioengineering Research Center, Weifang University of Science and Technology, Weifang 262700, China
Jingxiang Cui
College of Agronomy and Environment, Shandong Facility Horticulture Bioengineering Research Center, Weifang University of Science and Technology, Weifang 262700, China
Haizhou Dong
College of Food Science and Engineering, Engineering and Technology Center for Grain Processing of Shandong Province, Shandong Agricultural University, Taian 271018, China
Wentao Wang
College of Food Science and Engineering, Engineering and Technology Center for Grain Processing of Shandong Province, Shandong Agricultural University, Taian 271018, China
The purpose of this paper was to investigate the effect of high-intensity ultrasonication (HIU) pretreatment before enzymolysis on structural conformations of walnut protein isolate (WPI) and antioxidant activity of its hydrolysates. Aqueous WPI suspensions were subjected to ultrasonic processing at different power levels (600–2000 W) and times (5–30 min), and then changes in the particle size, zeta (ζ) potential, and structure of WPI were investigated, and antioxidant activity of its hydrolysates was determined. The particle size of the particles of aqueous WPI suspensions was decreased after ultrasound, indicating that sonication destroyed protein aggregates. The ζ-potential values of a protein solution significantly changed after sonication, demonstrating that the original dense structure of the protein was destroyed. Fourier transform infrared spectroscopy indicated a change in the secondary structure of WPI after sonication, with a decrease in β-turn and an increase in α-helix, β-sheet, and random coil content. Two absorption peaks of WPI were generated, and the fluorescence emission intensity of the proteins decreased after ultrasonic treatment, indicating that the changes in protein tertiary structure occurred. Moreover, the degree of hydrolysis and the antioxidant activity of the WPI hydrolysates increased after sonication. These results suggest that HIU pretreatment is a potential tool for improving the functional properties of walnut proteins.
