Dough Gas Research Articles

Effects of different gelatinization degrees of starch in potato flour on the quality of steamed bread

The effect of four kinds of potato flour with different gelatinization degrees on the quality of steam bread was investigated in the present study. Results showed that medium-well flour (MWF) and potato flakes (PF) steamed bread, particularly MWF steamed bread, possessed the desired product properties liked by consumers. The MWF steamed bread had the highest appearance score (42.78) and total sensory evaluation score (81.60), and the PF steamed bread exhibited the highest specific volume (1.84 mL/g) and taste score (43.05). An increase in the degree of potato flour gelatinization led to an increase in dough gas retention coefficient from 80.20 mL/100 mL to 85.17 mL/100 mL and a more uniform and dense dough microstructure. During dough preparation, the increased gelatinization degree of potato flours enhanced the hydroscopicity competition between potato starch and gluten, resulting in a flocculent gluten network and increased potato starch volume during steaming. During steaming, steamed bread with higher gelatinization degree of potato flour formed a homogenous and dense starch gel-gluten double network, making them softer with more uniform gas cells and larger specific volume. Thus, this study provides a perspective of the effect of starch gelatinization on steamed bread quality.

Instantaneous wheat dough relaxation by alternating current electric fields

Wheat dough exhibits poor processibility immediately after a mechanical strain, such as mixing or laminating. For proper dough processing, the relaxation of gluten network must occur during a process interrupting resting time of usually 10–25 min. The ability of electric fields to induce modifications in biological structures within seconds, makes an application of this technique reasonable for accelerating the structural relaxation during dough resting. Applying alternating current electric fields (AC-fields) to wheat dough, causes viscoelastic properties corresponding to those of rested dough: AC-fields (110–260 V, 1–5 s) increased extensibility and softness of dough corresponding to resting times up to 25 or rather 50 min. Based on this significant acceleration of structural relaxation, an almost continuously dough processing after a mechanical stress by a simple and short post-processing step without changing dough's gas release (ΔVtotal ≤ 3.0%) as well as holding capacity (Δgas retention ≤ 1.47%) and the textural properties of the product appears feasible.

Study on the mechanism of ultrasonic treatment impact on the dough's fermentation capability

The effects of ultrasonic treatment on the fermentation capability, water distribution of dough, and gluten's structural characteristics were investigated. Results suggest that the ultrasound works best under plate mode with the treatment duration and the power density being 6 min and 105 W/L, respectively. With the increment of power density, the bound water and free SH group content increased first and then decreased. Moreover, under ultrasound treatment, the β-sheet and random coil increased, while α-helix and β-turn decreased. Enhanced power density also caused the particle diameter and Young's modulus to plummet then increase. Free SH and Young's modulus correlated with Hm significantly (P < 0.05). Besides, SH, bound water, and the immobilized water displayed a strong correlation with Tx (P < 0.05). The results show that the appropriate ultrasound pretreatment can improve dough's gas retention capacity and enhance the gluten network structure's mechanical properties.

Thin film drainage dynamics of wheat and rye dough liquors and oat batter liquor

To obtain bread with a high loaf volume and homogeneous crumb, gas cells require sufficient stability until the discontinuous gas structure of dough is transformed into the continuous structure of bread. At the end of fermentation, dough gas cells are supposedly regionally separated by two air-water (A-W) interfaces and a liquid film. ‘Dough liquor’ (DL) or ‘batter liquor’ (BL), i.e. the supernatant after ultracentrifugation of dough and batter, respectively, is a model system for the fluid in these films. We report here on drainage dynamics of free-standing thin films (TFs) prepared from wheat and rye DLs and oat BL after applying a driving pressure of either 50 or 200 Pa at bulk concentrations lower than and equal to (‘native’) those in the respective supernatants obtained by ultracentrifugation. At lowered bulk concentrations, wheat and rye DL TFs were surrounded by planar and dimpled A-W interfaces, respectively, both of which were composed of weakly viscoelastic mixed protein-lipid films. In contrast, lipids stabilized dimpled oat BL TFs by migrating along their A-W interfaces and thus by generating Marangoni stresses. Liquid drainage and subsequent film rupture occurred rapidly in these TFs. At native bulk concentrations, TFs generally drained much slower and they were even found to be stable at small thicknesses (<100 nm). Here, lipids stabilized dimpled wheat DL and oat BL TF A-W interfaces by Marangoni effects or by forming a densely-packed layer, respectively. In addition, wheat DL and oat BL TFs at their native concentrations exhibited stratification due to layered structuring of micelles, which contributed to TF stability by exerting oscillatory structural forces. Thus, it can here be concluded that wheat DL and oat BL constituents at their native concentrations may contribute substantially to stabilizing gas cells in dough.

Impact of wheat endogenous lipids on the quality of fresh bread: Key terms, concepts, and underlying mechanisms.

While wheat (Triticum aestivum L.) flour contains only low levels of lipids (2.0% to 3.0%), they tremendously affect fresh bread quality. They are either starch (30% to 40%) or nonstarch (60% to 70%) lipids. While the former are important in bread staling, they affect neither bread loaf volume nor crumb structure as they are only set free at the very end of the baking process and prior to that they are not available because of their location inside starch granules. This review mainly focuses on wheat nonstarch lipids and how they impact on bread quality. Traditional approaches for investigating their role in bread making have been to use flours varying in bread making quality, to defat and reconstitute flour with (fractions of) the extracted lipids and/or to supplement flour with lipids from wheat or other sources. More recently, lipases have been successfully applied to investigate how wheat lipids affect bread making. It is generally accepted that their impact on bread loaf volume and crumb structure largely if not entirely relates to that on bread dough gas cells stability. However, today there are still different views and hypotheses on the mechanism(s) whereby they impact fresh bread quality. This review first defines and introduces the key terms, concepts, and theories related to lipids, lipases, and bread making. Next, the effects that wheat endogenous lipids and their enzymatically released hydrolysis products have on fresh bread properties and the mechanisms whereby they exert these effects are reviewed.

The role of non-starch polysaccharides in determining the air-water interfacial properties of wheat, rye, and oat dough liquor constituents

Dough gas cell stability is a prerequisite for obtaining breads with high specific volume and homogeneous crumb. The contribution of cereal endogenous non-starch polysaccharides (NSPs) to gas cell stability during wheat, rye, and oat bread making is still unclear. In this work, the aqueous phases from their fermented doughs were isolated as dough liquor (DL) by ultracentrifugation. The foaming, bulk shear rheology, and air-water (A-W) interfacial properties of wheat and rye DLs (treated with and without endoxylanase) and oat DL (treated with and without both lichenase and β-d-glucosidase) were studied. Enzymatic hydrolysis drastically reduced the apparent bulk shear viscosity of the different DLs and resulted in increased and decreased moduli (or magnitude) of the complex A-W interfacial shear viscosities of wheat and rye DLs, respectively. The latter implies that (non-hydrolyzed) rye DL arabinoxylan strengthens the A-W interfacial film consisting of adsorbed proteins and lipids. No measurable A-W interfacial shear viscosities were obtained for oat DL irrespective of whether its β-D-glucans were hydrolyzed or not. This is probably because lipids dominate the oat DL A-W interfaces. The knowledge generated provides a fundamental basis for specifically modifying the composition of the aqueous phase in wheat, rye, and oat doughs to improve the quality of mixed cereal breads.

Lipases in wheat flour bread making: Importance of an appropriate balance between wheat endogenous lipids and their enzymatically released hydrolysis products

Lipids are only minor wheat flour constituents but play major roles in bread making (BM). Here, the importance of a well-balanced lipid population in BM was studied by applying a lipase from Fusarium oxysporum in the process. Monogalactosyldiacylglycerols and N-acyl phosphatidylethanolamines were the most accessible lipase substrates. Hydrolysis thereof into their corresponding lysolipids was largely if not entirely responsible for loaf volume increases upon lipase application. Degradation of endogenously present lipids and enzymatically released lysolipids caused loaf volume to decrease, confirming that an appropriate balance between different types of lipids is crucial in BM. For optimal dough gas cell stability, the level of lipids promoting lamellar mesophases and, thus, liquid condensed monolayers needs to be maximal while maintaining an appropriate balance between lipids promoting hexagonal I phases, non-polar lipids and lipids promoting hexagonal II or cubic phases.

Ultrasonic investigation of the effects of composition on the volume fraction of bubbles and changes in their relative sizes in non-yeasted gluten-starch blend doughs

Interactions between water, gluten and starch during dough mixing alter the aeration properties of dough. Effects of composition on dough gas volume fraction and relative changes in bubble sizes of non-yeasted gluten-starch (G-S) blend doughs were investigated using density measurements and an ultrasonic transmission technique, respectively. At fixed water content, greater gluten content increased the air volume fraction, while frequency-dependent ultrasonic attenuation coefficient and phase velocity measurements indicated that the bubble sizes in the G-S doughs were larger. The latter outcome may be due to mixing to optimal conditions such that shorter mixing times for doughs of high gluten content lessened the number of bubble subdivision events during mixing. The effect of increased water content on the attenuation coefficient implied a decrease in mean bubble radius as elucidated using an ultrasonic model. Time evolutions of attenuation coefficient and phase velocity for G-S blend doughs had a similar trend to those of non-yeasted wheat flour doughs. However, the shifts in the frequency of the peaks observed in the ultrasonic parameters were noticeably slower for G-S blend doughs, implying that G-S blend doughs were more stable against disproportionation.

Effect of sugar on bread dough aeration during mixing

The aim of this study was to understand better dough aeration and in particular to determine how aeration during mixing differs between sugar containing and non-sugar containing dough through modelling and X-ray tomography. Batches of non-yeasted bread dough were mixed using both ‘plain’ and ‘strong’ flours with systematically varying granulated caster sugar formulations. A modified Tweedy 1-type mixer was used and mixer headspace pressure was controlled at various constant values to determine steady state dough aeration conditions. Pressure step-change experiments were used to determine aeration dynamics. A population balance model was fitted to the data to enable quantitative determination of the gas entrainment rate and disentrainment coefficient. X-ray computed tomography studies and uniaxial extensibility tests were also conducted to explore further the results of the aeration studies. This method enabled the model to be fitted to the aeration step-change response using only one parameter. The main effects of granulated sugar in dough were to increase the disentrainment coefficient and, to a lesser extent, to increase the entrainment rate. The combined effect of these was a reduction in dough gas content as granulated sugar content increased.

Effect of soybean addition on the rheological properties and breadmaking quality of wheat flour

AbstractThe effects of enzyme‐active full‐fat (EAFFSF), heat‐treated full‐fat (HTFFSF) and enzyme‐active defatted (EADSF) soy flours and commercial soy protein isolates (SPIs) on mixing properties and extensibility of dough, gluten formation, gas production and retention properties of dough and bread quality were studied. The soy products utilised in this study presented values of urease activity, nitrogen solubility index (NSI) and enthalpies of protein denaturation according to their previous heat processing. Soy products interfered in gluten formation, weakened dough strength and decreased dough gas retention capacity. Bread quality was negatively affected by soy product addition. The negative effects were exacerbated by an increase in soy/wheat ratio. Soybean protein state was identified as an important factor in determining dough and bread properties. Copyright © 2005 Society of Chemical Industry

Activation of waste brewer's yeast Saccharomyces cerevisiae for bread production

The waste brewer's yeast S. cerevisiae (activated and non-activated) was compared with the commercial baker's yeast regarding the volume of developed gas in dough, volume and freshness stability of produced bread. The activation of waste brewer's yeast resulted in the increased volume of developed gas in dough by 100% compared to non-activated brewer's yeast, and the obtained bread is of more stable freshness compared to bread produced with baker's yeast. The activation of BY affects positively the quality of produced bread regarding bread volume. The volume of developed gas in dough prepared with the use of non-activated BY was not sufficient, therefore, it should not be used as fermentation agent, but only as an additive in bread production process for bread freshness preservation. Intense mixing of dough results in more compressible crumb 48 hrs after baking compared to high-speed mixing.

Improving the Utility of Potato Pulp for Bread-Making by Fermentation with Rhizopus oryzae

Potato pulp is an agricultural by-product of the starch industry. To use it for bread-making, experiments were conducted to evaluate the bread-making quality of doughs to which intact potato pulp (IPP) and potato pulp fermented by Rhizopus oryzae NBRC 4707 (FPP) had been added. The use of IPP significantly decreased the baking quality of wheat flour by degrading the dough's physical properties and lowering the gas retention of the dough. The bread-making quality of dough to which potato pulp that had been fermented for 2 days by R. oryzae had been added was significantly better than that of dough to which IPP had been added. In particular, the bread quality, such as specific loaf volume (SLV), aspect and crumb grain, except for staling and color, were good. Increase of the dough's gas retention and gassing power were the primary reasons for its improvement. They seemed to be related to the decomposition of starch and fiber in potato pulp and the moderate pH lowering of potato pulp by organic acid formed in the fermentation process by R. oryzae. These results suggested that the fermentation with R. oryzae was useful because it improved the utility of potato pulp for bread-making.

Production and Characterization of Monoclonal Antibodies against Wheat Flour Diacylgalactosylglycerols

Seven immunoglobulin M (IgM)-type monoclonal antibodies were developed against wheat diacylgalactosylglycerols (MGDG). That with the highest titer, MG405, was characterized in detail using a solid phase enzyme-linked immunosorbent assay (ELISA). Inhibition experiments with galactose, glycerol, galactosylglycerol, and lipid standards containing fatty acids typical of those in MGDG indicated that MG405 was directed against the whole MGDG molecule rather than parts of its structure. Six other monoclonal antibodies, also IgM type, had similar specificities. Antibody binding was reduced by 30% when fetal bovine serum, used as antibody diluent and blocking agent, was replaced with gelatin in an ELISA carried out with purified MG405. The plasma cofactor β2-glycoprotein I (β2GPI) increased binding only slightly, suggesting that some other plasma cofactor may potentiate antibody binding to MGDG. MG405 also appeared not to be an intrinsically low-affinity antibody to β2GPI. Availability of antibodies such as MG405 could provide a valuable means of investigating polar lipid functionality in foods. Keywords: Anti-glycolipid antibody; monoclonal antibody; diacylgalactosylglycerols; MGDG; wheat; bread dough gas retention.

Strain Hardening and Dough Gas Cell-wall Failure in Biaxial Extension

Abstract Dough rheological properties were measured in biaxial extension using a modified Chopin Alveograph under conditions close to those of baking expansion. The resulting stress-strain curves showed power-law strain hardening, indicating an increase in stiffness with increasing inflation. This strain hardening was shown to be critical in determining the limit of bubble expansion, both in the Alveograph and in baking. A criterion for gas cell-wall instability and failure has been derived, which takes into account the strain and strain-rate hardening properties of dough during large extensional deformation. Differences in bubble stability were observed between different wheat cultivars at low rates of inflation close to those of baking expansion, but these differences disappeared at the higher rates normally associated with rheological testing.

Hypothesis for how linear glutenin holds gas in dough

A hypothesis is put forward to explain how dough resists uncontrolled expansion of gas cells. Hand kneading, mixer action or gas pressure shears swollen protein in dough. Shearing orients linear glutenin molecules parallel to the shearing forces. Molecules with little overlap are pulled apart in the shear gradient, giving them further chances of getting better overlap with other molecules. Mixing thus forms a well overlapped and coherent gluten. When starch granules are pressed together the protein phase between them gets squeezed out sideways and so undergoes shear at angles of up to 90° to the main direction of flow. A similar result is found if the swollen protein suspension is regarded as being pressed through the tortuous pores between granules: since there will be flow in every pore, the gluten is sheared locally parallel to the pore direction. The pores between starch granules form a continuous three-dimensional network; therefore the protein also forms such a network, which appears isotropic because the orientation is local. Unless a gluten is weak, bubbles can expand without bursting because this network of protein resists forces in all directions until gelling of starch sets the crumb structure; further expansion then tears the starch/protein matrix enough to release the pressure in the bubbles. Elasticity does not arise from stretching the bonds of polypeptide chains but because folded conformations of chains are incomparably more probable than unfolded ones. Brownian motion helps unfolded chains to refold rapidly. Relaxation during normal proof times, while letting unfolded chains refold, does not destroy all orientation and overlap. Part of the action of fungal α-amylase may be to widen the pores between starch granules, reduce the size of small granules that could block such pores and delay starch gelation by slowing the entry of water. Fat could ease the relative movement of granules and protein, and the work of expanding gas cells. The fibrils seen when flour particles are wetted may illustrate the effects on glutenin of shear, produced in this case by sudden release of osmotic pressure. Moulding by sheeting gives an overall direction of orientation (DO) lacking in newly mixed dough. For the surfaces of a rolled sheet this DO lies in the machine direction, but inside the sheet it is sideways. In one-piece bread the asymmetry of gas cells results from easier expansion in the main DO, i.e. along the loaf. In four-piece bread the lack of room to expand horizontally forces cells to elongate vertically.