Cereal Chem. 70:333-338   |  VIEW ARTICLE

Thermal Behavior of Potato Amylose and Enzyme-Resistant Starch from Maize.

D. Sievert and P. Wursch. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

The thermal properties of potato amylose (degree of polymerization 5,500) and of enzyme-resistant starch (RS) (degree of polymerization 65) from autoclaved maize starch in a concentrated aqueous system (22%, w/w) were studied by differential scanning calorimetry (DSC). Heating of amylose and RS in the DSC instrument to 180 C (heating rate 5 C/min) gave melting transitions at 153.6 and 139.8 C, respectively, indicating disordering of fairly thermostable regions. This heating to high temperatures was accompanied by a partial thermal degradation of the linear amylose and RS chains. Reappearance of endotherms during repeated heating and the appearance of exotherms during each cooling phase suggested (re)association of chains from the polymer melts of both amylose and RS. Association of amylose and RS chains appeared to start between 80-75 C and 60-55 C, respectively. Whereas interactions between the long amylose chains were reduced at cooling rates of greater than 10 C/min, interchain contacts between the shorter RS chains seemed not to be affected by the rate of cooling. In the presence of the complexing agent L-alpha- lysophosphatidylcholine (LPC), the process of association of linear chains was competitively affected by the formation of inclusion complexes of the linear chains with LPC. At an LPC concentration of 10% (w/w), complex formation dominated, and no association of amylose or RS chains was observed.