Maltodextrin molecular weight distribution influence on the glass transition temperature and viscosity in aqueous solutions

The intrinsic functional properties (viscosity and glass transition temperature) of three corn maltodextrins (and their mixtures) in various amount of water are predicted from the molecular weight distribution. The concentration dependence of the viscosity at constant temperature is predicted over a broad range of concentration using a combination of the Mark-Houwink-Sakurada (with a rather low exponent (0.337) compared to other carbohydrates) and Spurlin-Martin-Tennent's exponential models. The construction of a viscosity-concentration master-curve is successfully attempted when the shift factor is the viscosity average molecular weight. The glass transition temperature for dry maltodextrin samples is predicted in the light of previous investigations performed on the series of maltose oligomers. A new effective average molecular weight, characteristic of the glass temperature, is introduced and determined by the plasticizer/plasticized ratio. Couchman's model is well adapted to starch water systems and is proven here to be also appropriate for maltodextrin water mixtures where the heat capacity increment depends on the number average molecular weight. (C) 2004 Elsevier Ltd. All rights reserved.