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B.-H. Lee, Graduate School of Life Sciences and Biotechnology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-ku, Seoul, 136-701, South Korea, J.-A. Han, and S.-T. LIM, Graduate School of Biotechnology, Korea Univ., 5-1, Anam-Dong, Sungbuk-Ku, Seoul, 136-701, South Korea. (1)Justification. Waxy rice cake is a popular traditional food in Korea. But retrogradation of the waxy rice cake during storage induces texture hardening and degrading of quality. The hydroxypropylation renders a hydrophilic property to starch and weakens the internal bonds between starch chains. The b-amylase releases maltose sequentially from the starch, producing short outer chains. (2) Objectives. The objective of our study is to retard starch retrogradation and thus increase storage stability using hydroxypropylated or b-amylase-treated waxy starches. (3) Methods. The waxy rice cake was produced by steam-cooking with waxy rice flour or starch, and stored at 4 °C for the periods up to 7 days. The texture of the waxy rice cakes was determined using a texture analyzer (TA) and sensory analysis. Thermal properties were mesured using a differential scanning calorimeter (DSC). (4) Results. Hardness measured by TA and sensory test, and retrogradation enthalpy by DSC were significantly reduced by using the hydroxypropylated waxy starches. The degree of retrogradation was reduced in the order of : hydroxypropylated waxy rice starch > hydroxypropylated waxy corn starch > waxy rice flour > waxy corn starch > waxy rice starch. The retrogradation was reduced also by the b-amylase treatment. But the effect of enzyme was lower than hydroxypropylation. In conclusion, Hydroxypropyation and b-amylase treatment were effective in retarding the retrogradation of waxy rice cake, improving the textural and sensory properties. (5) Significance. The results from this study can be used in industrial application of the modified starch in waxy rice or other starch products, in order to retard retrogradation. Especially for waxy rice cake, using the modified starch will increase shelf life, and reduce consumer inconveniences of re-cooking the retrogradated waxy rice cake.
Session 93, Carbohydrate: General
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