pubs.acs.org/JAFC Published on Web 12/31/2009 © 2009 American Chemical Society 1180 J. Agric. Food Chem. 2010, 58, 1180–1188 DOI:10.1021/jf902753f Relationship of Granule Size Distribution and Amylopectin Structure with Pasting, Thermal, and Retrogradation Properties in Wheat Starch SANDEEP SINGH Department of Food Science and Technology, Guru Nanak Dev University, Amritsar-143005, India NARPINDER SINGH* Department of Food Science and Technology, Guru Nanak Dev University, Amritsar-143005, India NAOTO ISONO Graduate School of Bioresources, Mie University, Tsu 514-8507, Japan TAKAHIRO NODA National Agricultural Research Center for Hokkaido Region, Memuro, Hokkaido 082-0081, Japan Starches separated from 18 Indian wheat varieties were evaluated to see relationship of granule size distribution and amylopectin structure with pasting, thermal, and retrogradation properties. Average diameter of A-, B-, and C-granules among different starches varied between 23.0 and 28.5, 10.0 and 12.0, and 2.3 and 2.7 μm, respectively. Amylopectin chain length distribution varied significantly, short length chains (DP 6-12) and long length chains (DP > 24) ranged between 44.5 and 52.4% and 3.7 and 6.5%, respectively, whereas amylose content ranged between 18.2 and 28.8%. Short length chains of amylopectin had inverse relationship with starch gelatinization temperatures T o , T p , and T c . Starches with higher crystallinity had higher enthalpy of gelatinization and lower swelling power. Paste characteristics were mainly dependent upon granule type and all pasting parameters except pasting temperature, showed significant positive correlations with A-granules and negative with the proportion of B- and C-granule. KEYWORDS: Granule size; retrogradation; amylopectin; wheat starch INTRODUCTION Different size and shapes of starch granules build up in the endosperm during the development of grain. The mature endo- sperm in wheat consists of two distinct types of starch granules that are large, disk-shaped, and termed A-granules as well as small and spherical, termed as B-granules. Bechtel et al. ( 1 ) and Raeker et al. ( 2 ) reported for wheat starch having another distinct class of small C-granules that initiated 21 days after anthesis. The different granule types show significant differences in chemical composition and functional properties such as amylose, lipid content, and gelatinization characteristics ( 3 , 4 ). Starch is composed of two glucose polymers, amylose and amylopectin. Amylopectin with its multiple branched chains of (1-4)-R-glucans interlinked by (1-6)-R-linkages is usually the major component of starch, with the essentially unbranched amyl- ose making up the minor fraction. The molecular architecture of amylopectin and its molecular arrangement within the granule is related to the granule size ( 5 ). The ratio of long branch chains to short branch chains affects the shape of the amylopectin mole- cules, which affects their packing and, in turn, the morphology and size of the starch granule ( 6 ). The functional properties of starch are affected by amylose content, branched chain-length distribu- tion of amylopectin ( 7 , 8 ), phosphate monoester, phospholipid, and lipids content ( 9 , 10 ), starch granule size distribution ( 2 , 11), crystalline structures ( 12 ), and granular architecture ( 13 ). In wheat starches, amylopectin is considered to contribute to water absorp- tion, swelling, and pasting of starch granules, whereas amylose and lipids tend to retard these processes ( 14 ). Jane and Chen ( 15 ) concluded that the amylopectin chain length distribution and amylose molecular size produce synergistic effects on the viscosity of starch pastes. The present study assesses the characteristics of starches from different Indian wheat varieties with regard to structural, physicochemical, granule size distribution and proportion, pasting, thermal, and retrogradation properties. The objective of our study was to investigate the structural and physicochemical features that provide diverse functional pro- perties to wheat and to develop a relationship between these properties. *To whom correspondence should be addressed. Phone: 0183- 2258802 ext 321. Fax: þ91-183-2258820. E-mail: narpinders@ yahoo.com.