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Colloid Polym Sci (2012) 290:14811491
DOI 10.1007/s00396-012-2674-2
ORIGINAL CONTRIBUTION
Effects of NaOH treatment of cereal starch granules on the extent of granular starch hydrolysis
U. Uthumporn & Y. N. Shariffa & A. Fazilah & A. A. Karim
Received: 5 July 2011 /Revised: 12 April 2012 /Accepted: 28 April 2012 /Published online: 13 May 2012 # Springer-Verlag 2012
Abstract Effect of NaOH treatment on granular hydrolysis of cereal starches was studied and granular starch hydrolyzing enzyme is used to hydrolyze native and NaOH-treated starch for 24 h. The dextrose equivalent value of NaOH-treated starch increased significantly compared to native starch, i.e., 2838 % for corn, 737 % for rice, but no significant increase for corn starch. Scanning electron microscopy micrographs showed that NaOH treatment caused an enlargement of pores and degrades the surface of starch granules. Hydrolyzed-treated starch exhibited rougher surface and more porous granules compared to native starch. The swelling power and pasting properties of NaOH-treated starches were markedly altered after hydrolysis. X-ray pattern of all starches showed no changes and the amylose content decrease significantly after hydrolysis, which could due to extensive degradation of amorphous region. Evidently, NaOH treatment below gelatinization temperature was effective in enhancing the degree of granular starch hydrolysis.
Keywords Starch . Granular hydrolysis . Amylolytic enzyme . NaOH . Cereal
Introduction
Starch granules have a semi crystalline, three-dimensional structure composed of branched amylopectin and lightly branch linear amylose. There are also some proteins and lipids in cereal starch granules [1, 2]. The granular structure
of starch can be changed under certain conditions, and the degree of change is highly associated with the original structure of the starch granule. Heat/moisture treatment, as shown by Hoover and Manuel [3] causes changes of crystallinity of starch granules, and these changes mainly occurred in the amorphous regions by amylose association. Vasanthan et al. [4] studied the reactivity of different starch samples towards acetylation and cationization. The results showed that starches from different origin have different reactivity. The reactivity of the starch surface is very low, and reactants have to penetrate into the granule to react with the starch molecules as illustrated many researchers [57], and it is generally thought that amorphous regions are more important than crystalline regions in chemical modification.
Enzymatic hydrolysis of...