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Comparison of Physical Properties of Wheat Starch Gels with Different Amylose Content

¹Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8572, Japan. ²National Food Research Institute, Kannondai, Tsukuba, Ibaraki 305-8642, Japan. ³Corresponding author. Fax: +81-298-38-7996. Phone: +81-298-38-8031. Email: tomokos@affrc.go.jp. ⁴National Agricultural Research Center for Western Region, Nishifukatsucho, Fukuyama, Hiroshima 721-8514, Japan. ⁵Institute of Agricultural Engineering, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8572, Japan.

The effects of amylose content and other starch properties on concentrated starch gel properties were evaluated using 10 wheat cultivars with different amylose content. Starches were isolated from grains of two waxy and eight nonwaxy wheat lines. The amylose content of waxy wheat lines was 1.4–1.7% and that of nonwaxy lines was 18.5–28.6%. Starch gels were prepared from a concentrated starch suspension (30 and 40%). Gelatinized starch was cooled and stored at 5°C for 1, 8, 16, 24, and 48 hr. The rheological properties of starch gels were studied by measuring dynamic viscoelasticity with parallel plate geometry. The low-amylose starch showed a significantly lower storage shear modulus (G′) than starches with higher amylose content during storage. Waxy starch gel had a higher frequency dependence of G′ and properties clearly different from nonwaxy starches. In 40% starch gels, the starch with lower amylose showed a faster increase in G′ during 48 hr of storage, and waxy starch showed an extremely steep increase in G′. The amylose content and concentration of starch suspension markedly affected starch gel properties.