Effect of oil and shortening in rice bread quality: Relationship between dough rheology and quality characteristics.

One of the main problems with gluten-free breads is their texture and their rapid staling. Fats are widely used for the improvement of texture and other quality parameters in gluten-free breads. The effect of oil and shortening in rice-breads quality and its correlation with dough rheology has been analyzed. The inclusion of oil increased the specific volume of the breads and reduced their hardness, particularly with lower levels of hydration, whereas shortening did not modify specific volume or reduced it when hydration levels were higher. Oil, at levels of up to 30%, reduced the cohesiveness, springiness and resilience of breads, as well as the brightness of the crust, and increased the a* and b* values. Breads with oil also exhibited a greater number of pores per cm2 , especially in doughs with higher levels of hydration. An inverse correlation between G' and G'' and bread specific volume has been observed, being the reciprocal-Y model a better predictor than the linear model to relate the bread specific volume. PRACTICAL APPLICATIONS: This study showed that the type and quantity of fat added in rice based breads affect the bread quality in a different way. In general, it can be said that the incorporation of up to 20% oil improved rice based breads. Oil increased the specific volume, the a* and b* parameters of the crust and the cell density. It also decreases hardness, cohesiveness, springiness, resilience, and the L* parameter. Converse to breads made with oil, the addition of shortening can negatively affect the quality of the breads. Moreover, the correlation analysis has demonstrated that the study of dough rheology could be a good predictor of gluten-free bread quality.

Mixture design of rice flour, maize starch and wheat starch for optimization of gluten free bread quality.

Gluten-free bread production requires gluten-free flours or starches. Rice flour and maize starch are two of the most commonly used raw materials. Over recent years, gluten-free wheat starch is available on the market. The aim of this research was to optimize mixtures of rice flour, maize starch and wheat starch using an experimental mixture design. For this purpose, dough rheology and its fermentation behaviour were studied. Quality bread parameters such as specific volume, texture, cell structure, colour and acceptability were also analysed. Generally, starch incorporation reduced G* and increased the bread specific volume and cell density, but the breads obtained were paler than the rice flour breads. Comparing the starches, wheat starch breads had better overall acceptability and had a greater volume than maize-starch bread. The highest value for sensorial acceptability corresponded to the bread produced with a mixture of rice flour (59 g/100 g) and wheat starch (41 g/100 g).