Publication no. C-1999-0215-06R |  VIEW ARTICLE

Initial Heating Temperature and Native Lipid Affects Ordering of Amylose During Cooling of High-Amylose Starches.

Kathryn W. Boltz (1) and Donald B. Thompson (2). (1) Department of Food Science, Penn State University, 111 Borland Laboratory, University Park, PA 16802. (2) Corresponding author. E-mail: <dbt1@psu.edu> Phone: 814/863-2950. Fax: 814/863-6132. Cereal Chem. 76(2):204-212. Accepted September 28, 1998. Copyright 1999 American Association of Cereal Chemists, Inc.

Formation of ordered structures from disordered amylose is practically important. The thermal behavior of high-amylose maize starches was studied during cooling, following heating, and during subsequent reheating. Four commercial high-amylose genotype maize starches with varying amylose contents (ae du, ae su2, and ae [nominally both 50 and 70% amylose]) were heated to either 120, 140, 160, or 180°C, cooled to 5°C, and reheated to 180°C in a differential scanning calorimeter. Each starch was studied with its native lipid, as well as in reduced-lipid and lipid-free form. On cooling of lipid-containing starches, two distinct exotherms were observed and attributed to amylose-lipid complex formation and to amylose chain association. A distinct exotherm at approximately 75°C was attributed to amylose-lipid complex formation. The exotherm attributed to amylose chain association on cooling varied according to the initial heat treatment, lipid level, and starch type. Starches with higher amylose contents showed larger exotherms on cooling. For initial heat treatments to 120 or 140°C, a broad exotherm beginning at approximately 95°C was observed on cooling. In contrast, for initial heat treatments to 160 and 180°C, a sharper exotherm with a peak temperature below approximately 55°C was observed. Upon reheating, samples that had been initially heated to 120 or 140°C showed a peak at >140°C that was attributed to the melting of ordered amylose. Starches initially heated to 160 or 180°C did not show this peak. This work illustrates that initial heating temperature, as well as lipid content and amylose content, all affect amylose chain association during cooling. Thus, this work suggests strategies for controlling ordering of amylose during processing.