Influence of pregelatinised tapioca starch and transglutaminase on dough rheology and quality of gluten-free jasmine rice breads

It has been well recognised that the only effective treatment for coeliac disease is a persistent life-long avoidance of food products containing wheat and similar cereal grains. At present, there is still substantial demand for gluten-free products that meet consumer needs in terms of sensory quality, conveniences and price values. This work investigated the characteristics of gluten-free jasmine rice (JR) bread and its quality improvement through the applications of pregelatinised tapioca starch (PG) and transglutaminase (TGase). The JR bread had rather low bread volume (1.9 cm3/g) and high crumb hardness. In order to adjust dough viscoelasticity and to improve bread quality, the PG was substituted for the rice flour at the level up to 30% w/w. It was found that all JR-based batters were viscoelastic solid. The substitution of PG decreased the dough elasticity slightly but increased the resistance to deformation, thus, permitting better expansion of gas cells during baking. In breadmaking, the specific loaf volume increased to 2.4 cm3/g with the substitution of PG at 10% w/w but was suppressed at higher amount of the substitution. The replacement of PG also resulted in lower crumb hardness and chewiness. An addition of TGase at 0.1–1% (flour weight basis) increased the bread volume and decreased crumb hardness and chewiness. Moreover, increasing TGase concentration showed a tendency to decrease bread loaf volume and increased crumb hardness and chewiness. Cohesiveness and springiness of all the breads were, however, unaffected. Overall, both pregelatinised tapioca starch and transglutaminase are promisingly useful ingredients for producing gluten-free jasmine rice bread with better bread quality.