Surface protein coverage and its implications on spray-drying of model sugar-rich foods: Solubility, powder production and characterisation

We have investigated the amount of protein required to produce amorphous sugar powders through spray-drying. Pea protein isolate was used as a model plant protein and sodium caseinate was used as a model dairy protein. Powder recovery in a laboratory spray dryer was used as a measure of the ease of spray drying for a given formulation. More than 80% of amorphous sucrose and fructose was produced with the addition of sodium caseinate, while the pea protein isolate was able to produce only recoveries of less than 50% of amorphous sucrose. Sensitivity of low molecular weight surfactants has been demonstrated using both ionic (sodium stearoyl lactylate) and non-ionic (polysorbate-80) surfactants. Spray-dried powders were subjected to physico-chemical characterisation and dissolution experiments. The maximum solubility of all powders was obtained after 5 min of dissolution. The solubility of the sodium caseinate increased by 6-7% in the presence of fructose and low molecular weight surfactants. The solubility of the amorphous powders of sucrose-pea protein isolate was found to be lower than amorphous powders of sucrose-sodium caseinate and fructose-sodium caseinate. The addition of sucrose in water increased the solubility of the pea protein isolate from 16.84% to more than 83%. The non-ionic surfactant (Tween-80) has reduced the solubility of sucrose-pea protein isolate-Tween-80 powders significantly (p < 0.05) compared to those of sucrose-pea protein isolate-sodium stearoyl lactylate powders. The solubility of sucrose-sodium caseinate powders was comparable to that of pure sodium caseinate, indicating that addition of sucrose into 0.13% sodium caseinate does not have any significant effect on the solubility of this protein at this concentration. (C) 2011 Elsevier Ltd. All rights reserved