Texture properties of rice cakes made of rice flours treated with 4-α-glucanotransferase and their relationship with structural characteristics

Rice flours were treated using a thermostable 4-α-glucanotransferase (GTase) from Thermus aquaticus for 1, 3, and 48 h. Molecular weight of modified rice starch rapidly decreased within 1 h of reaction, then slowed down. As the reaction proceeded, the proportions of short (less than DP 11) and long (greater than DP 30) branched chains of modified starch increased, whereas the proportion of medium chains decreased. Rice cakes were prepared with native and GTase-treated rice flours (substitution at 5%) and kept for 3 and 21 h. Texture profile analysis indicated significantly increased hardness, adhesiveness, chewiness, and resilience in rice cakes containing treated rice flours. Sensory analysis revealed that the rice cakes containing 48 h-treated flour had significantly increased springiness, hardness, toughness, and adhesiveness during both storage periods. Meanwhile, it displayed the lowest starch-like attribute and crumbliness. These results suggested that the substitution for 48 h GTase-treated rice flour could retard the retrogradation of rice cakes.