Effects of starch gelatinization, rheological properties, and a top cover on the height of steamed cakes made with rice flour and wheat flour

Abstract

The expansion and shrinkage behaviors of steamed rice flour and wheat flour cakes were investigated. The maximum height of rice flour batter-cake (sample during steaming) was much lower than that of wheat flour batter-cake. The gelatinization temperature (T_gel) was determined to be 83.8 °C for the rice flour batter and 81.5 °C for the wheat flour batter. The storage modulus (G’) and loss modulus (G”) at 75 °C (below the T_gel) and 80 °C (just below the T_gel) were much higher in the rice flour batter than in the wheat flour batter. This suggests that rice flour batter is more resistant to expansion (harder batter) than wheat flour batter. The shrinkage rate of steamed rice flour cake was much higher than that of steamed wheat flour cake. The G’ and G” values of rice flour batter were slightly lower than those of wheat flour batter at 85 °C (above the T_gel). In addition, the height of gelatinized layer at the maximum height of rice flour batter-cake was much lower than that of wheat flour batter-cake. The lower gelatinized layer, the softer layer, and thus the larger shrinkage will occur. To improve the less expansion and greater shrinkage of steamed rice flour cake, a novel steaming method in which the top surface of the batter is covered by a light and sturdy top cover was proposed. It was demonstrated that the height was significantly higher in cake steamed with a top cover than in that steamed without a top cover.