Impact of Overhead Pressure During Mixing on the Quality of Sandwich Bread

Abstract

This paper presents the impact of overhead pressure (constant pressure and pressure modulation) during mixing on important mixing parameters (maximal power level and the corresponding time (t_PEAK)), dough properties after mixing and fermentation (dough voidage and growth rate), and bread characteristics (such as specific volume, void fraction, and crumb microstructure). The overhead pressure during mixing, which was done with air as overhead pressure, did not significantly affect the maximal power level and t_PEAK, but significantly impacted dough and bread characteristics. Mixing at high pressure, i.e., 0.5 bar above atmospheric pressure, led to higher dough voidage at the end of mixing, resting, and sheeting. Moreover, high-pressure mixing led to higher dough growth, resulting in the attainment of desired expansion ratio of 3.5 much early (after 70 min fermentation). The bread obtained from this condition had the largest specific volume of 4.29 ml/g and void fraction of 82.98% and possessed one of the largest crumb cell sizes. On the other hand, mixing under atmospheric pressure (1 bar) and step decrease to partial vacuum (i.e., 0.2 bar below atmospheric pressure) from atmospheric pressure and high pressure led to dough with relatively low void fraction and slow dough growth rate during fermentation. For the same fermentation time (i.e., 70 min), these conditions resulted in bread with similar characteristics but had significantly smaller measured parameters than other conditions. Moreover, dough mixed under these conditions had to be fermented for an additional 10 min (i.e., total of 80 min) to attain bread with specific volume and void fraction similar to that of other studied conditions. Overall, it was found that overhead pressure during mixing mainly impacted the dough void fraction which, in turn, impacts the dough growth rate during fermentation and the final bread characteristics.