Effect of preservatives on the functional properties of tapioca starch: analysis of interactions

The effect of different levels of potassium sorbate or sodium benzoate addition on the water sorption behavior and on the mechanical properties of freeze-dried tapioca starch gel was studied. It was observed that the addition of potassium sorbate or sodium benzoate to starch before the gelatinization process increased the amount of water sorbed by the system, but experimental moisture content of the mixture was lower than the one predicted by a mass balance, revealing the existence of an interaction between starch and the preservatives. In general, in the range of water activity 0.755-0.976, most of the preservative was bounded to starch. Mechanical properties of the powder obtained after freeze drying of gels were also influenced by the addition of the preservatives: an increase in bulk density, higher cohesiveness and initial Young modulus was observed after antimicrobial addition. Results obtained showed that sorbate and benzoate interact with tapioca starch and that this interaction has a great influence on system behavior. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.