Structural Characterization of Rice Starch in Rice Cake Modified by Thermus scotoductus 4-α-Glucanotransferase (TSαGTase)

Authors: Seo, N.-S.¹; Roh, S.-A.¹; Auh, J.-H.¹; Park, J.-H.¹; Kim, Y.-R.¹; Park, K.-H.¹

Source: Journal of Food Science, Volume 72, Number 6, August 2007 , pp. C331-C336(1)

Publisher: Blackwell Publishing

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Abstract:

Rice cake was produced with a thermostable 4-α-glucanotransferase from Thermus scotoductus (TSαGTase). Starch molecular fine structure, texture, and retrogradation for the enzymatically prepared rice cake were investigated and compared to those for control rice cake. The amylose content in TSαGTase-treated rice cakes decreased, whereas branched and linear malto-oligosaccharides ranging from maltose to maltoheptaose increased slightly. The average molecular weight of the enzyme-treated rice starch in rice cake decreased as amylopectin macromolecules were cleaved and reorganized into small amylopectin clusters. The number of shorter side chains (degree of polymerization [DP] < 9) increased, whereas the number of longer side chains (DP > 10) decreased through the disproportionation reaction of TSαGTase. After 24 h of storage at 4 °C, the enzyme-treated samples demonstrated significantly lower melting enthalpy of retrograded starch (0.4 mJ/mg) compared to that of the control (1.4 mJ/mg). The results indicated that TSαGTase treatment effectively inhibited starch retrogradation in rice cakes. It is suggested that the reduction of amylose content, the rearrangement of amylopectin, and the production of malto-oligosaccharides caused by TSαGTase treatment are responsible for the ineffective molecular reassociation of rice starch in rice cake.

Keywords: 4-α-glucanotransferase (TSαGTase); rice cake; starch retrogradation

Document Type: Research article

DOI: 10.1111/j.1750-3841.2007.00428.x

Affiliations: 1: Authors Seo and Roh are with SPC Food Safety Center and Samlip General Foods Co., Seongnam 463-839, Korea. Author Auh is with Dept. of Food Science & Technology, Chung-Ang Univ., Anseong 456-756, Korea. Author Park is with Foods Ingredients Center, CJ Co., Seoul 152-059, Korea. Author Kim is with Center for Agricultural Biomaterials and Dept. of Biosystems & Biomaterials Science and Engineering, Seoul Natl. Univ., Seoul 151-921, Korea. Authors Seo and Park are with Center for Agricultural Biomaterials and Dept. of Food Science & Biotechnology, Seoul Natl. Univ., Seoul 151-921, Korea. Direct inquiries to author K.-H. Park ( )., Email: parkkh@snu.ac.kr

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