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Effects of Spray Drying and Freeze Drying on the Properties of Protein Isolate from Rice Dreg Protein


This work was done to investigate the effects of different drying methods in the preparation of rice protein isolates (RPIs), as the understanding could provide useful information regarding applications of plant proteins in the food industry. RPI from rice dreg protein, a cheap by-product from the production of rice syrups, was extracted using an alkali solution along with isoelectric precipitation, and subsequently dried by freeze drying (FD-RPI) or spray drying (SD-RPI). The differences in biochemical, physical, and structural characteristics were observed for the dried proteins. SD-RPI had higher protein solubility and emulsifying activity at the pH values between 5 and 11, with higher foaming capacities (127.08 ± 2.25 % compared to 118.83 ± 2.71 %) than FD-RPI. However, FD-RPI had larger mean diameter (2,114.2 ± 79.6 nm compared to 490.4 ± 44.8 nm of SD-RPI), higher water/oil holding capacity (p < 0.05), and thermal stability. In addition, FD-RPI contained more β-turn structures (43.04 % compared to 25.81 %), and less β-sheet and random coils than SD-RPI, indicating that the more compact and ordered conformations of FD-RPI might be related to their physicochemical and functional properties. The choice of drying method could significantly influence physicochemical and conformational properties of RPIs, consequently determining their specific functional properties. The understanding of drying effects on their properties could assist in selecting the appropriate drying method to optimize the utilization of RPIs in the food industry.

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The authors gratefully acknowledge the financial support provided by the Programs of State Key Laboratory of Food Science and Technology of Nanchang University (SKLF-KF-201006 and SKLF-MB-201005); Key Program for Oil Processing & Quality Control of the Department of Science and Technology (Gankefa 2010J217), Graduate Innovative Research Program (YC09A031), Science and Technology Platform Construction Program (2010DTZ01900), Leading Technological Innovation Team Program (Gankefa 2010J156) of Jiangxi province.

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Correspondence to Hua Xiong.

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Zhao, Q., Xiong, H., Selomulya, C. et al. Effects of Spray Drying and Freeze Drying on the Properties of Protein Isolate from Rice Dreg Protein. Food Bioprocess Technol 6, 1759–1769 (2013).

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  • Rice dreg protein
  • Rice protein isolate
  • Functional properties
  • Physicochemical properties
  • Spray drying
  • Freeze drying