Influence of electrostatic interactions on behavior of mixed rice glutelin and alginate systems: pH and ionic strength effects

The influence of pH (2-7) and ionic strength (0-200 mM NaCl) on the properties of hydrolyzed rice glutelin (HRG), alginate, and their mixtures in aqueous solutions was investigated using turbidity, zeta-potential, and microscopy measurements. Soluble or insoluble complexes could be formed between HRG and alginate by manipulating solution conditions such as HRG:alginate ratio, pH, and ionic strength. Relatively small complexes that were relatively stable to aggregation and sedimentation over a wide range of pH conditions could be formed using a 3:1 HRG to alginate mass ratio. The addition of salt (NaCI) to solutions containing HRG-alginate complexes weakened the electrostatic attraction between them, which led to release of the protein. As a result, the protein molecules tended to interact with other protein molecules (rather than polysaccharide molecules) leading to the formation of precipitates and sediments. The electrostatic complexes formed in this study may be a useful means of extending the utilization of rice proteins as functional ingredients in food and beverage products. (C) 2016 Elsevier Ltd. All rights reserved.