Molecular structure and enzymatic hydrolysis properties of starches from high-amylose maize inbred lines and their hybrids Lingshang Lin a, 1 , Dongwei Guo b, 1 , Jun Huang a , Xudong Zhang b , Long Zhang a , Cunxu Wei a, * a Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern ProductionTechnology of Grain Crops, Yangzhou University, Yangzhou 225009, China b Key Laboratory of Biology and Genetic Improvement of Maize in Arid Area of Northwest Region, Ministry of Agriculture, Northwest A & F University, Yangling 712100, China article info Article history: Received 14 November 2015 Received in revised form 23 February 2016 Accepted 1 March 2016 Available online 3 March 2016 Keywords: Maize High-amylose starch Molecular structure Enzymatic hydrolysis In vitro digestion abstract High-amylose maize starch has health benefits and special industrial uses. In this study, starches were isolated from normal maize and high-amylose inbred and hybrid maizes. Their molecular structure and enzymatic hydrolysis properties were investigated and analyzed. The high-amylose hybrid maize starch contained lower amylose, intermediate component, amylopectin long branch-chains, and amylopectin average chain length, and higher amylopectin short branch-chains than did high-amylose inbred maize starch. High-amylose maize starch was more resistant to a-amylase and amyloglucocidase hydrolysis and had a significantly lower hydrolysis rate coefficient than normal maize starch did. The native, gelatinized and retrograded starches of the high-amylose hybrid maize had significantly higher rapidly digestible starch and lower resistant starch than those of the high-amylose inbred maize. The retrogradation of gelatinized starch markedly increased the resistance of high-amylose starch to in vitro digestion. The high contents of amylose and intermediate component and the long branch-chains of amylopectin increased the resistance of maize starch to enzymatic hydrolysis and in vitro digestion. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Starch consists of two main components: amylose and amylo- pectin. Many studies have reported that high-amylose starch also contains an intermediate component that has branched structures with branch-chains longer than amylopectin but molecular weights smaller than amylopectin and similar to amylose (Jiang, Campbell, Blanco, & Jane, 2010; Jiang et al., 2015; Li, Jiang, Campbell, Blanco, & Jane, 2008). Sepharose CL-2B gel-permeation chromatography (GPC) is generally used to investigate the molecular weight distri- bution (amylopectin, amylose, and intermediate component) of native starch, especially for high-amylose starch (Alves, Polesi, Aguiar, & Sarmento, 2014; Jiang et al., 2010, 2015; Kubo et al., 2010; Li et al., 2008; Marti, Pagani, & Seetharaman, 2011; Pinto et al., 2015; Yoo et al., 2009; Zhang, Zhao, & Xiong, 2010; Zhu et al., 2015). Amylose content has significant effects on structural and func- tional properties of starch. Starches with high-amylose content have a high content of resistant starch, a portion of starch that cannot be hydrolysed in the upper gastrointestinal tract and func- tions as a substrate for bacterial fermentation in the large intestine for digestion (Carciofi et al., 2012; Englyst, Kingman, & Cummings, 1992; Man et al., 2012; Regina et al., 2006; Slade et al., 2012; Zhu et al., 2012). High-amylose cereal starch is presently of interest because it can lower glycaemic and insulin responses and reduce the risk for developing type II diabetes, obesity, and cardiovascular disease through its resistant starch (Nugent, 2005). In addition, high-amylose starch is also potentially of special value for industrial utilization. Therefore, many high-amylose cereal varieties have been developed via mutation or transgenic breeding approaches (Carciofi et al., 2012; Regina et al., 2006; Slade et al., 2012; Zhu et al., 2012). Abbreviations: AAG, Aspergillus niger amyloglucosidase; GPC, gel-permeation chromatography; HPAEC, high-performance anion-exchange chromatography; PPA, porcine pancreatic a-amylase; RDS, rapidly digestible starch; RS, resistant starch; SDS, slowly digestible starch. * Corresponding author. College of Bioscience and Biotechnology, Yangzhou University, Yangzhou 225009, China. E-mail address: cxwei@yzu.edu.cn (C. Wei). 1 Lin L. S. and Guo D. W. contributed equally to this work. Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd http://dx.doi.org/10.1016/j.foodhyd.2016.03.001 0268-005X/© 2016 Elsevier Ltd. All rights reserved. Food Hydrocolloids 58 (2016) 246e254