Carbohydrate Polymer. 2017 Nov 1;175:265-272   IF：6.044

Yunfei Liu,Jun Chen, Shunjing Luo, Cheng Li ,Jiangping Ye,Chengmei Liu,Robert G.Gilbert

Abstract: Amylose, one of the components of starch, is a glucose polymer consisting largely of long, linear chains with a few long-chain branch points. The chain-length (molecular weight) distribution (CLD) of the component chains of amylose can provide information on amylose biosynthesis-structure-property relations, as has been done previously by fitting amylopectin CLDs to a model with physically meaningful parameters. Due to the presence of long chains, the CLD of amylose can currently best be obtained by size-exclusion chromatography, a technique that suffers from band-broadening effects which alter the observed distribution. The features of the multiple regions present in amylose chain-length distributions are also difficult to resolve, an issue that combines with band broadening to compound the difficulty of analysis and subsequent parameterization of the structural characteristics of amylose. A new method is presented to fit these distributions with biologically meaningful parameters in a way that accounts for band broadening. This is achieved by assuming that band broadening takes the form of a simple Gaussian over a relatively small region and that chain stoppage is a random process independent of the length of the substrate chain over the same region; these assumptions are relatively weak and expected to be frequently applicable. The method provides inbuilt consistency tests for its applicability to a given data set and, in cases where it is applicable, allows for the first nonempirical parameterization of amylose biosynthesis-structure-property relations from CLDs by using parameters directly linked to the activities of the enzymes responsible for chain growth and chain stoppage. Pregelatinized starch was made from indica rice starch using a so-called “improved extrusion cooking technology” (IECT) under 30%–70% moisture content. IECT-pregelatinized starch (IPS) had higher water solubility and water absorbability compared to native starch at low temperature. For pasting properties, the breakdown and setback viscosities of IPS were significantly (p < 0.05) lower than native starch, suggesting improved gel stability and reduced short-term retrogradation. the rice starch granules lost their integrity in ips, and formed a honeycomb-like structure with increased moisture content in the raw material. these properties can be explained in terms of molecular structural features, particularly the large reduction in the size of molecules, but without significant changes in the chain-length distributions of amylopectin component, and no significant change in amylose fraction. these results indicate that iect is suitable for preparing ips with desirable water solubility and gel stability properties.

KEY WORDS：Improved extrusion cooking technology; Indica rice starch; Physicochemical properties; Pregelatinized starch; Structure

https://www.ncbi.nlm.nih.gov/pubmed/?term=Physicochemical+and+structural+properties+of+pregelatinized+starch+prepared+by+improved+extrusion+cooking+technology.