Bread making is a hydro-thermal process; therefore, knowing the behaviour of themain constituents of the flour at different temperatures allows control of the quality ofthe end-product. Mixing and thermal characteristics were studied using the Mixolabsystem and response surface methodology was used to investigate the influence of particlesize distribution of the flour, pH and the addition of hemicellulase enzyme on thethermo-mechanical behaviour of the whole rye flour and on bread quality. A centralcomposite 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/kgof flour), was used. The results indicated that thermo-mechanical variables – waterabsorption, development time, dough stability, protein weakening, starch gelatinization,starch gelling and cooling setback – as well as bread quality are influenced by thethree factors investigated.Significant correlations were found between water absorption and pH, enzyme level,fineness modulus and their interactions. Dough stability was significantly influencedby all the independent variables, as well as by the interaction between pH and finenessmodulus. Starch gelling and cooling setback were influenced by the interaction betweenpH and enzyme level. Concerning bread quality, both porosity and specific volume wereaffected by enzyme level and pH, as well as by the interaction between fineness modulusand enzyme level.
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