Rheological studies on mixtures of corn starch and konjac-glucomannan

Rheological properties of corn starch (CS) and konjac-glucomannan (KM) mixtures (total polysaccharide concentration: 3.50 wt%, CS/KM ratios: 10/0, 9/1, 8/2, 7/3, 6/4) were studied as a function of mixing ratio and storage time by measuring storage and loss shear moduli and by observing the large deformation and fracture behaviour. The viscoelastic behaviour of dispersions of CS plus water (2.10-3.50 wt%, 3.50 wt% = 10/0) was intermediate between a weak gel and an elastic gel, and dispersions of KM plus water (0.35-1.40 wt%) showed a behaviour similar to a concentrated polymer solution. The behaviour of CS and KM mixture was intermediate between a concentrated polymer solution and a weak gel. KM does not interact synergistically with CS to promote the formation of ordered structure. The breaking stress for CS and KM mixtures increased slowly with storage time than for CS alone. KM prevented syneresis of corn starch during storage. (C) 1998 Elsevier Science Limited. All rights reserved.