Optimization of gluten-free bread formulation containing leblebi flour and evaluation of dough and bread properties

Gluten-free bread is a complex system formed by many components which differently interacts during processing. For the development of a high quality gluten-free bread, an overall consideration of ingredients and process conditions is thus required. Since the ingredients have different composition and water absorption capacities, dramatic differences in the quality of gluten-free bread could be observed by altering the amount of flour, hydrocolloid and water added into the dough. For a proper adjustment of the levels of the bread ingredients, a statistical approach like response surface methodology is very useful. Leblebi is a traditional snack food in Turkey obtained from chickpea, a legume characterized by a high proteins and fiber content. Since most of the ingredients used in gluten-free formulations are rich in starch, the incorporation of chickpea flour can be considered as a way to improve gluten free bread nutritional quality. In the first part of the study, a three factor central composite design was developed in order to optimize the levels of leblebi flour, hydroxypropyl methyl cellulose (HPMC) and water. Gluten-free bread samples of 20 different formulations were prepared and the following dependent variables were measured: bake loss, specific volume, crumb moisture, crumb textural parameters and crumb and crust color. According to the ANOVA results, the models for each individual response were significant (p values between p<0.05 to p<0.0001) with satisfactory lack of fit and R2 values. The most dominant factor, with a significant influence on almost each response, was the water addition level. Bake losses, specific volumes, crumb moisture and hardness values were mainly affected by HPMC and water addition levels. Leblebi flour caused significant changes in the color parameters of both crust and crumb, in particular a decrease of the lightness was observed. By considering the results, an optimized formulation having desirable response values and a high leblebi flour content (xx%) was identified. The model was also validated by performing baking experiments with the optimized gluten-free formulation. The second part of the study was focused on the characterization of the optimized dough supplemented with 25% Leblebi flour in comparison with the control sample, containing only rice flour. The two doughs were prepared with a Farinograph by adding different amounts of water in order to reach the same consistency (about 130 UB). The dough leavening properties were investigated by using both Rheofermentometer and image analysis. Although leblebi flour addition caused a dough development reduction (ca. 20%), both samples were characterized by satisfactory leavening properties with a C02 retention capacity higher than 98%. The results obtained via image analysis reflected the rheofermentographic behaviour to indicate the effectiveness of this method to measure dough leavening characteristics. Dough were also characterized by dynamic oscillatory tests in order to highlight differences in their viscoelastic behaviour.