Prediction of rye dough behaviour and bread quality using response surface methodology

Bread making is a hydro-thermal process; therefore, knowing the behaviour of the main constituents of the flour at different temperatures allows control of the quality of the end-product. Mixing and thermal characteristics were studied using the Mixolab system and response surface methodology was used to investigate the influence of particle size distribution of the flour, pH and the addition of hemicellulase enzyme on the thermo-mechanical behaviour of the whole rye flour and on bread quality. A central composite face-centered design, with two levels of fineness modulus (1.78 and 1.26), two levels of pH (6.5 and 3.8) and three levels of added enzyme (0, 50 and 100 mg/kg of flour), was used. The results indicated that thermo-mechanical variables - water absorption, development time, dough stability, protein weakening, starch gelatinization, starch gelling and cooling setback as well as bread quality are influenced by the three factors investigated. Significant correlations were found between water absorption and pH, enzyme level, fineness modulus and their interactions. Dough stability was significantly influenced by all the independent variables, as well as by the interaction between pH and fineness modulus. Starch gelling and cooling setback were influenced by the interaction between pH and enzyme level. Concerning bread quality, both porosity and specific volume were affected by enzyme level and pH, as well as by the interaction between fineness modulus and enzyme level.