Research Article Received: 10 September 2014

Revised: 18 November 2014

Accepted article published: 27 November 2014

Published online in Wiley Online Library:

(wileyonlinelibrary.com) DOI 10.1002/jsfa.7028

Physicochemical and crystalline properties of heat–moisture-treated rice starch: combined effects of moisture and duration of heating Xiangli Kong,a,b Dan Qiu,c Xiaoting Ye,d Jinsong Bao,a Zhongquan Sui,d* Jiewei Fane* and Wenzhou Xiange Abstract BACKGROUND: Currently there is much interest in the application of physical modification techniques such as heat–moisture treatment (HMT). The effects of HMT on normal and waxy rice starches, subject to different levels of moisture content and duration of heating, were investigated. RESULTS: Water solubility index (determined at 90 ∘ C) decreased after HMT for normal and waxy rice starches, while swelling power (determined at 90 ∘ C) showed inconsistent results (decrease for normal type, increase for waxy type) after HMT. Values in pasting parameters of normal and waxy rice starch increased initially, but the extent of increase slowed down with moisture content and length of treatment increasing. HMT decreased gelatinization temperatures with 4 h and 8 h treatment, but when length of treatment was prolonged to 16 h gelatinization temperature increased. Degree of crystallinity decreased for all treatments, and decreased much more at higher levels of moisture content. CONCLUSION: Variations in levels of moisture content and duration of heating had significant effects on physicochemical and crystalline properties to different extents. © 2014 Society of Chemical Industry Keywords: hydrothermal treatment; rice starches; moisture content; length of treatment; functional properties

INTRODUCTION Starch comprises two major types of biomacromolecules: amylose and amylopectin. Amylose is an essentially linear biopolymer of 𝛼-D-(1,4)-glucosyl units with few branches connected by a 𝛼-D-(1,6)-glucosyl linkage, while amylopectin has a much higher density of branching attached by a 𝛼-D-(1,6)-glucosyl linkage in the main 𝛼-D-(1,4)-glucosyl chains. Amylose content and amylopectin structural parameters affect functional properties of starch1 and hence determine its applications. However, this native structure of starch, subject to various food-processing conditions, exhibits low resistance to high shear rate, thermal decomposition, high retrogradation and syneresis.2 Therefore, native starch is usually modified to overcome these shortcomings. Starch modification is commonly achieved through derivatization (etherification, esterification, cross-linking and grafting), decomposition (acid or enzymatic hydrolysis and oxidization) and physical treatment (using heat or moisture).3 Currently, there is much interest in the application of physical modification techniques, such as heat–moisture treatment (HMT), which modifies the physicochemical properties of starches by facilitating starch chain interactions within the amorphous and crystalline domains.4 HMT is an important physical method using environmentally safe processes with low cost and without by-products of chemical reagents.5 – 7 HMT is defined as a physical modification that involves the treatment of the starch granules at a low moisture content (

Physicochemical and crystalline properties of heat-moisture-treated rice starch: combined effects of moisture and duration of heating.

Currently there is much interest in the application of physical modification techniques such as heat-moisture treatment (HMT). The effects of HMT on n...
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