Evaluating Dough Density Changes During Fermentation by Different Techniques

Abstract

Producing an aerated bread dough starts at the mixing stage where air bubble nuclei are incorporated into the dough. During fermentation, the production of CO 2 , due to yeast's metabolic activities, causes the bubbles to increase in size thereby increasing the volume and reducing the density. Therefore, the way in which the density of the dough is reduced and the dough's ability to retain gas plays an important part in the production of good loaf volume. A number of studies have used different approaches to examine the effects of fermentation conditions on the rheology of dough. The internal pressure of fermenting dough has been measured by placing the dough in a glass cylinder (Matsumoto et al 1971). The expansion of the dough resulting from fermentation was studied by Miller at al (1954), who measured the expansion by displacement of a weak salt solution. In another study (Marek and Bushuk 1966), the buoyancy of fermenting dough was measured by placing it on a balance in a constant temperature bath of mineral oil. However, despite the importance of dough density changes as an indicator of gas holding capacity of the dough, a direct comparison of how the density changes as the dough ferments using a variety of measurement techniques has not been reported.The objective of this note was to investigate the effect of measurement techniques on evaluation of dough density by measuring the decrease in density of fermenting dough under different geometrical constraints and comparing the results. To achieve this, the volume of the expanding dough was measured over time using three methods: 1) dough height increase within a graduated cylinder, 2) water displacement following free expansion of subsamples of the dough, and 3) radial expansion of dough constrained between two thick acrylic plates (measured using digital imaging). MATERIALS AND METHODSDough samples used in these experiments were prepared from Canadian Western Red Spring (CWRS) wheat flour by mechanical dough development using the standard Canadian Short Process Method (Preston et al 1982) as described by Elmehdi et al (2003). One mixed dough was used for a given dough density measurement technique, and three replicates were examined for each technique. At the end of mixing, subsamples were immediately removed from the dough piece. In the free expansion method, typically 20 subsamples were removed from the mixed dough, while for the other methods, only one subsample was required to perform the measurement. After measuring the mass of the subsample, it was placed in the apparatus used to measure the volume.For the free expansion method, the subsamples were placed in the proofing cabinet and the volume of the expanding dough was measured by taking one subsample at ≈5-min intervals. For all three methods, the apparatus and the subsample were placed in a proofing cabinet that was set at normal proofing conditions (37°C and 83% relative humidity) (Preston et al 1982). The change in the volume of the fermenting dough with time was then measured using one of the thr...

Assessment of Bread Dough Expansion during Fermentation

“…The density decrease observed is consistent with density measurements reported by Campbell et al (2001). The larger discrepancy observed with the data reported by Elmedhi et al (2007) is explained by differences in wheat flour strength and formulation (Elmedhi et al 2007). …”

“…This is also true for the final mean rate V f , but to a lesser extent. In order to compare volume expansion followed by our Dough expansion with the horizontal method for different initial water contents: unfilled squares 56%, ex symbols 58%, unfilled triangles 60% (w/w flour basis), T f fermentation temperature three methods with other methods reported in the literature (Campbell et al 2001;Elmedhi et al 2007), we compiled some data read from their charts in Table 4 and calculated the overall densities of the dough from the actual experiments. The density decrease observed is consistent with density measurements reported by Campbell et al (2001).…”

“…A rapid freezing rate was also resulting in a better preservation of the final dough volume. Recently, Elmedhi et al (2007) investigated three techniques to evaluate dough density changes during fermentation, one of them using digital imaging. Romano et al (2007) also used a camera to record volume expansion and proposed a modified Gompertz model to describe the leavening process.…”

Monitoring the dynamic density of wheat dough during fermentation

“…This discrepancy among the methods could be partly due to differences in the sample size. Elmehdi et al (2007) found that when dough density was measured with fermenting small samples of dough (3 g) and immersing them in a specific gravity bottle, the rate of decrease was lower because smaller dough volumes released more gas per unit volume and therefore their expansion occurs at a lower rate. Smaller sample sizes have a larger surface to volume ratio and the possibility to lose gas during proofing increases.…”

“…They concluded that monitoring dough density is a valid and sensitive technique that allows for better investigation of aerated food products. Elmehdi et al (2007) evaluated three methods for measuring dough density. They found that even though dough density followed the same pattern (i.e., decreasing with fermentation time), the absolute measurement varied depending on the method used.…”