Molecular breakdown of corn starch by thermal and mechanical effects

Abstract The molecular weight reduction of corn starch at 30–43% moisture during thermal treatment at temperatures 90–160 °C and during well-defined thermomechanical treatment at temperatures 90–140 °C was investigated. Thermal treatment resulted, during the first 5 min in a decrease in molecular weight as measured by intrinsic viscosity, after which longer heating had no significant effect. Higher moisture contents and temperatures generally resulted in more breakdown, although the effect diminished at higher temperatures. The decrease in intrinsic viscosity during thermomechanical treatment at relatively low temperatures and moisture contents was shown to be only dependent on the maximal shear stress. At higher temperatures, thermomechanical breakdown could be split into a mechanical part depending on maximal shear stress and a thermal breakdown part, which was again time-dependent on the shorter time-scales only. Higher moisture content during thermomechanical treatment resulted in more thermal breakdown and lowered the shear stresses required for mechanical breakdown. Consequences for process design are discussed briefly.

[1]  I. Hayakawa,et al.  Degradation Profiles of Potato Starch Melts Through a Capillary Tube Viscometer , 2001 .

[2]  F. Meuser,et al.  Expansion and Functional Properties of Corn Starch Extrudates Related to their Molecular Degradation, Product Temperature and Water Content , 2002 .

[3]  A. Donald,et al.  Macromolecular degradation of extruded starches measured by HPSEC-MALLS , 2001 .

[4]  R. Boom,et al.  Understanding Molecular Weight Reduction of Starch During Heating-shearing Processes , 2003 .

[5]  P. P. Kundu,et al.  Effect of alcoholic, glycolic, and polyester resin additives on the gelation of dilute solution (1%) of methylcellulose , 2003 .

[6]  J. L. Willett,et al.  Extrusion of waxy maize starch: melt rheology and molecular weight degradation of amylopectin , 1997 .

[7]  L. Wen,et al.  Starch fragmentation and protein insolubilization during twin-screw extrusion of corn meal , 1990 .

[8]  K. R. Bhattacharya,et al.  Characteristics of Gel‐chromatographic Fractions of Starch in Relation to Rice and Expanded Rice‐Product Qualities , 1986 .

[9]  L. Diosady,et al.  Degradation of Wheat Starch in a Single-Screw Extruder: Mechano-Kinetic Breakdown of Cooked Starch , 1985 .

[10]  I. Hayakawa,et al.  Effect of Longer Heating Time on Depolymerization of Low Moisturized Starches , 1997 .

[11]  Description of Extrudate Characteristics in Relation to the Shear Stress of Plasticised Starches Determined In-line , 2002 .

[12]  O. Campanella,et al.  High moisture twin-screw extrusion of sago starch: 1. Influence on granule morphology and structure , 1996 .

[13]  I. Hayakawa,et al.  Depolymerization of Molten‐Moisturized‐Starch Molecules by Shearing‐Force under High Temperature , 1995 .

[14]  J. Mua,et al.  Relationships between Functional Attributes and Molecular Structures of Amylose and Amylopectin Fractions from Corn Starch , 1997 .

[15]  M. Hanna,et al.  Macromolecular and functional properties of native and extrusion-cooked corn starch , 1990 .

[16]  J. V. Soest,et al.  The influence of maltodextrins on the structure and properties of compression-molded starch plastic sheets , 1999 .

[17]  V. Davidson,et al.  Degradation of Wheat Starch in a Single Screw Extruder: Characteristics of Extruded Starch Polymers , 1984 .

[18]  P. Colonna,et al.  Interrelationships between thermomechanical treatment and macromolecular degradation of maize starch in a novel rheometer with preshearing , 1987 .

[19]  J. Byars Jet Cooking of Waxy Maize Starch: Solution Rheology and Molecular Weight Degradation of Amylopectin , 2003 .

[20]  L. Janssen,et al.  The effect of thermomechanical treatment on starch breakdown and the consequences for process design , 2004 .