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Rheological Properties of Starch Gels from Wheat Mutants with Reduced Amylose Content

¹National Food Research Institute, Kannondai, Tsukuba, Ibaraki 305-8642, Japan. ²Corresponding author. Fax: +81-29-838-7996. Phone: +81-29-838-8031. E-mail: tomokos@affrc.go.jp ³National Agricultural Research Center for Western Region, Nishifukatsucho, Fukuyama, Hiroshima 721-8514, Japan. ⁴National Agriculture and Food Research Organization, Kannondai, Tsukuba, Ibaraki 305-8517, Japan. ⁵National Agricultural Research Center for Western Region, Zentsuji, Kagawa 765-8508, Japan. ⁶National Institute of Crop Science, Kannondai, Tsukuba, Ibaraki 305-8518, Japan.

Wheat lines with reduced amylose content were recently produced by single and double mutation from a low-amylose line, Kanto 107. They are appropriate for clarifying the influence of amylose content on starch gel properties because of their similar genetic background. When measured using the concanavalin A method (ConA), the total amylose content of isolated starches from Kanto 107 and three mutants (K107Afpp4, Tanikei A6599-4, K107Wx2) was 24.8, 18.5, 7.1, and 1.7%, respectively. Results of differential scanning calorimetry (DSC) showed that the difference in amylose content strongly affected gelatinization conclusion temperature and enthalpy. We prepared 30 and 40% starch gels and measured their dynamic shear viscoelasticity using a rheometer with parallel plate geometry. Compressive and creep-recovery tests were conducted under uniaxial compression. The storage shear modulus correlated highly with the amylose content of starch in 30 and 40% starch gels. The creep-recovery test showed a clear distinction in creep curves among starch samples. When the compressive force required for 50, 80, and 95% strains was compared, starch gels with lower amylose content showed lower compressive force at 50% strain. Waxy starch gel (K107Wx2) showed higher compressive force at strain >80% than other samples due to its sticky property.