The effects of non-starch polysaccharides on the extent of gelatinisation, swelling and alpha-amylase hydrolysis of maize and wheat starches

Starch hydrolysis (alpha-amylase) and gelatinisation characteristics were evaluated in the presence of five different polysaccharides (arabic, carrageenan, guar, pectin and xanthan) with different starch to solution ratios and polysaccharide concentrations therein. Using relatively high starch/solution ratios (1: 10) at concentrations (<5%) of the polysaccharides that permitted some starch mobility (in the solutions) it was possible to restrict swelling of starch granules and consequently restrict the amount of starch gelatinisation. With lower solution ratios (1:0.8, 1: 1.7, 1:3.3 and 1:5.0, especially 1:0.8 and 1: 1.7) it was possible to model the effects of the polysaccharides in terms of displacing water and restricting gelatinisation with respect to the (modified) Flory-Huggins equation. With and without taking into account specific hydration of the polysaccharides, it was possible to show a linear relationship between the end point of gelatinisation (T-c) and the volume fraction of water in the system (v(1)). The implications in terms of product processing have been discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.