Optimization of coconut protein deamidation using protein-glutaminase and its effect on solubility, emulsification, and foaming properties of the proteins

The optimization of deamidation by protein-glutaminase (PG) on coconut protein (CP) and its effect on protein properties were studied. The optimum conditions were determined using response surface methodology (RSM). It was found that the optimum conditions were: enzyme: substrate ratio (E/S) of 36 U/g protein, temperature of 50 degrees C and pH of 7.0. The selected functional properties of treated CP subjected to deamidation for 15 min, 6 h, and 12 h, respectively were determined. Comparatively to control sample, the solubility of deamidated CP was improved at pH = 3.0 (p <= .05). Water-holding and oil-holding capacities were not different from control after PG deamidation. Emulsifying activity index (EAI) of 15 min deamidated sample was decreased, while EAIs of 6 and 12 h deamidated protein were not different from control. Emulsifying stability index of all deamidated samples were increased. Foaming capacity was increased after PG deamidation, while the foaming stability was decreased. It was also found that small molecular proteins were increased after PG deamidation. (C) 2017 Elsevier Ltd. All rights reserved.