EFFECTS OF ENZYMATICALLY MODIFIED AMYLOPECTIN ON THE RHEOLOGICAL PROPERTIES OF AMYLOSE-AMYLOPECTIN MIXED GELS

Branched alpha-dextrins with different molecular weights were prepared fi om waxy maize. A series of beta-limit dextrins was prepared from a lpha-dextrins and native amylopectin. The fine structure of the dextri n samples was investigated by debranching, and was found to be similar to the unit chain distribution of native amylopectin. The absolute mo lecular weights of alpha- and beta-limit dextrins and commercial potat o amylose were determined by gel-permeation chromatography (GPC) and w ith a dual light-scattering detector Solubilized potato amylose and al pha- and beta-limit dextrins were mixed at different ratios to give a total concentration of 8%. Dynamic viscoelastic measurements showed th at gel formation of amylose was highly dependent both on the ratio of amylose to alpha-dextrin and on the molecular weight of alpha-dextrin. alpha-Dextrin caused an increase of storage modulus, G, when the amyl ose: alpha-dextrin ratio was low and the molecular weight of alpha-dex trin was high. The high-molecular-weight alpha-dextrin influenced amyl ose gelation in the same way as native waxy maize starch, but the medi um-and low-molecular-weight alpha-dextrans weakened the gel formation, especially at a ratio of 25:75 (amylose, alpha-dextrin). When low-mol ecular-weight beta-limit dextrins were mixed with amylose, the resulti ng gels were more rigid than those in which amylose was mixed with cor responding alpha-dextrins. When high-molecular-weight beta-limit dextr ins were mixed with amylose, the resulting gels were weaker.