Dough Liquor Research Articles

A lipase based approach for studying the role of wheat lipids in bread making

While endogenous wheat lipids exert a major effect on bread quality, little is known on the way they impact on bread loaf volume (LV). Here we altered wheat flour lipid composition during bread making using lipases in situ. Lipopan F, Lecitase Ultra, and surfactants increased LV to similar extents. The increases in bread LV as a result of these enzymes were related to decreased levels of galactolipids and phospholipids and concomitant increased ‘lyso’-lipid as well as free fatty acid (FFA) levels. The FFA formed were transferred to the free lipid fraction, while the ‘lyso’-lipids remained in the bound lipid fraction. For optimal gas cell stabilisation, an equilibrium between the lipid classes present and hence, the type of mesophase formed, is essential. Sufficient levels of lipids forming lamellar mesophases and lipids forming hexagonal I mesophases, which respectively form condensed monolayers or emulsify (deleterious) non-polar lipids in dough liquor, are needed.

Fermentation affects the composition and foaming properties of the aqueous phase of dough from soft wheat flour

A quality characteristic of bread is that it has a homogeneous and fine crumb structure. The latter depends on the number and size of gas cells present in dough as well as their stabilization during fermentation and baking. Discontinuities in the gluten–starch matrix result in liquid films formed from the dough aqueous phase taking over gas cell stabilization. This is especially important in late fermentation. How fermentation affects (the composition and properties of) the dough aqueous phase is unclear. In the present study, the dough's aqueous phase was isolated as dough liquor (DL) from unfermented and fermented dough made from flour and water (with or without added sugar and salt). Fermentation increased DL yield and changed its composition. With regards to surface active proteins, especially the extractability of α-amylase/trypsin inhibitors and puroindolines (PINs) in DL increased. More foam of higher stability was formed from DL from (defatted) fermented dough than from that from (defatted) flour-water dough. PINs were specifically enriched in foam from DL from fermented dough. Finally, supplementation of dough with the latter DL sample yielded bread with finer gas cells than those of control bread. Thus, fermentation enhances the foaming properties of DL, which is also translated in improved bread quality.

Effect of Temperature on the Solubility of CO2 in Bread Dough

Dough expansion during fermentation is caused by CO2 production by yeast, and its transfer from liquid state in the dough liquor to gaseous phase in the gas cells. The liquid-gas equilibrium is controlled by the solubility of CO2 in the dough and by the Henry coefficient. The solubility of CO2 in bread dough was measured for different temperatures with a specific device based on the evolution of the pressure during fermentation at constant volume. The measurements range from 15 to 40°C. Data obtained was extrapolated to 0 and 50°C. Values were found between 1.6 × 10−5 and 5 × 10−6 g CO2 kPa−1 g−1 LPD, at 0 and 50°C, respectively (LPD: Liquid Phase of Dough).

Role of glycolipids in breadmaking

AbstractIn wheat flour used for breadmaking, glycolipids are essential “endogenous surfactants” (1). Bread volume and crumb structure of wheat flour‐based bakery products are influenced by glycolipids, without the decisive mode of action being conclusively known. Little information on how glycolipids from other plant sources perform as wheat flour improvers is available. In this paper we review our work done on revealing the baking performance of the four major glycolipid classes present in commercial lecithins (sterol glucosides (SG), acylated sterol glucosides (ASG), cerebrosides and digalactosyl diacylglycerides (DGDG). Our purpose is to better understand the role of these substances in the baking process. Our results suggest that there are two groups of glycolipids with excellent baking performance. Both groups were found to have an impact on the dough liquor rather than on the gluten‐starch matrix. The cerebrosides and DGDG most likely influenced the overall baking result by directly stabilizing the dough liquor/gas cell interface, while ASG and SG did this indirectly through a synergistic effect with a dough liquor constituent, most probably the endogenous flour lipids.

Molecular Structure and Baking Performance of Individual Glycolipid Classes from Lecithins

The potential of individual glycolipid classes from lecithins (soybean, rapeseed, and sunflower) in breadmaking was determined in comparison to classical surfactants such as diacetyltartaric acid esters of mono- and diacylglycerides (DATEM), monoacylglycerides, sodium stearoyl-2-lactylate (SSL), and two synthetic glycolipids by means of rheological and baking tests on a microscale. A highly glycolipid-enriched sample containing the entire glycolipid moiety of the lecithin was obtained using an optimized batch procedure with silica gel. This sample was subsequently used to gain individual glycolipid classes through column chromatography on silica gel. The major glycolipid classes in the lecithins, digalactosyl diacylglycerides (1), sterol glucosides (2), acylated sterol glucosides (3), and cerebrosides (4), were identified and characterized. All isolated glycolipid classes displayed excellent baking performance. A better baking activity than that of the classical surfactants was displayed by 1, 3, and 4 and an equivalent baking activity by 2. The same glycolipid classes, except 3, of different lecithin origin showed only slight differences in their baking activities, due to different fatty acid compositions. Furthermore, the glycolipid classes influenced the crumb structure significantly by improving the crumb softness and grain. Interestingly, none of the glycolipid classes showed significant antistaling effect. A direct effect on the overall rheological behavior of the dough was only found for the commercial surfactants. However, the rheological effect seen on gluten isolated from surfactant-containing dough revealed that the surfactants could be divided into two main groups, one of them directly forming and stabilizing liquid film lamellae through adsorption to interfaces and the other indirectly increasing the surface activity of the endogenous lipids in the flour. The results suggest that in wheat dough, glycolipids seem to have an impact on the dough liquor rather than on the gluten-starch matrix.

Effect of Environmental Stress during Grain Filling on the Soluble Proteome of Wheat (Triticum aestivum) Dough Liquor

The influence of genotype and environment on a soluble wheat dough liquor proteome was studied for four cultivars grown under field conditions and under hot/dry and cool/wet regimes by two-dimensional electrophoresis followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole time-of-flight mass spectrometry. Although the four cultivars had similar patterns, differences in the relative abundances of some components were observed. Similarly, some differences were observed between the control samples and the samples grown under cool/wet and hot/dry conditions. These included differences in the abundances of storage proteins belonging to the 7S globulin (vicilin-like) and alpha-globulin families and of protective proteins including members of the serpin, described as allergens, and chitinase families. A number of novel annotations were made as compared to previous work on the dough liquor of cv. Hereward, including two 19 kDa alpha-globulins, precursors of endochitinases A and C, and several polypeptides belonging to the 7S globulin (vicilin-like) family.

Surface Layer Properties of Dough Liquor Components: Are They Key Parameters in Gas Retention in Bread Dough?

Gas cell stability during bread making is controlled by both surface and bulk properties. This paper is focused on studying the surface properties of the water-soluble phase of the dough, the dough liquor (with and without lipids), as well as the composition of the air/water interface. Using infrared reflection measurements, we showed that in lipid-poor liquor, proteins are the dominant species present at the air/water interface. With complete liquor (including the lipids), a mixed interface of protein and lipids is obtained. However, the presence of lipids in the surface layer did not significantly affect the surface pressure. We also added enzymes to the flour to evaluate in what way the surface-active properties of the liquor components can be affected. These results were compared to the effect of adding a surfactant [diacetyl tartaric esters of mono- and diglycerides (DATEM)]. Biobake 10804, a xylanase that increased the arabinoxylan content of the dough liquor, decreased the surface pressure and increased the dilational modulus in lipid-poor liquor. This effect was not observed with the liquor including the lipids. Lipopan 50 BG, a 1,3-specific lipase, increased the surface pressure of the liquor that included the lipids. Lipopan F BG, which converts polar lipids to their lyso form, strongly increased the surface pressure not only in the lipid-containing liquor but also in the lipid-poor liquor. DATEM, as expected, increased the surface pressure while strongly decreasing the dilational modulus. Results of these studies were used to help explain changes in loaf volume observed in a series of baking tests, using the same enzymes and additives. This led to the conclusion that the effect of surface-active components alone cannot account for the larger loaf volumes observed. Clearly, both the effect of bulk and interfacial rheological properties should be considered together when explaining gas cell stability. © Springer Science+Business Media, Inc. 2006.

Composition and surface properties of dough liquor

The composition and surface properties of dough liquor isolated by ultracentrifugation have been characterised. Addition of ascorbate had no effect and salts only a limited effect, on the yield, protein content and composition of the dough liquor. Fourier transform infrared spectroscopy (FT-IR) revealed the presence of proteins, lipids, starch oligosaccharides together with the non-starch polysaccharide, arabinoxylan. At high dilution the dough liquor air:water interface was dominated by protein, with surface tensions of around 55 mN/m and high surface elasticity. As the concentration was increased, surface tensions dropped to around 40 mN/m for undiluted dough liquor. This was accompanied by the interface becoming less elastic, and indicated that dough liquor lipids were interacting and disrupting the protein films in concentrated dough liquor. Dough liquors from de-fatted flours remained elastic and gave surface tension values of around 50–55 mN/m even at low dilution, indicating that removal of the lipids gave rise to a purely protein stabilised interface. Addition of salt to the dough had the greatest effect on the surface properties, both reducing surface tension and reducing surface elasticity, probably because the charge screening effect of the salt improved the dispersion of lipids in the dough liquor, thus enabling it to disrupt the protein films more effectively. These results indicate that the aqueous phase of bread doughs lining the gas cells would give rise to a mixed protein:lipid interface. Such interfaces are unstable, and would contribute to the instability of the foam structure of risen dough. In addition they show that dough ingredients may modify gas cell stability (and hence may affect crumb structure), by altering the composition and properties of the aqueous phase of doughs.

The identification of foam-forming soluble proteins from wheat (Triticum aestivum) dough

Proteomic methods have been used to identify foam-forming soluble proteins from dough that may play an important role in stabilising gas bubbles in dough, and hence influence the crumb structure of bread. Proteins from a soluble fraction of dough (dough liquor) or dough liquor foam have been separated by two-dimensional gel electrophoresis, and 42 identified using a combination of matrix-assisted laser desorption/ionization-time of flight and quadrupole-time of flight analyses. Major polypeptide components included beta-amylase, tritin and serpins, with members of the alpha-amylase/trypsin inhibitor family being particularly abundant. Neither prolamin seed storage proteins nor the surface-active protein puroindoline were found. Commonly used dough ingredients (NaCl, Na L-ascorbate) had only a minor effect on the 2-DE protein profiles of dough liquor, of which one of the more significant was the loss of 9 kDa nonspecific lipid transfer protein. Many proteins were lost in dough liquor foam, particularly tritin, whilst a number of alpha-amylase inhibitors were more dominant, suggesting that these are amongst the most strongly surface-active proteins in dough liquor. Such proteins may play a role determining the ability of the aqueous phase of doughs, as represented by dough liquor, to form an elastic interface lining the bubbles, and hence maintain their integrity during dough proving.

Effect of Puroindolines on the Breadmaking Properties of Wheat Flour

ABSTRACTThe role of lipid‐binding proteins from wheat seed (puroindolines) on the breadmaking properties of wheat flour was investigated by determining the relationship between breadmaking quality and puroindoline content in samples of 32 wheat cultivars. An inverse relationship was mainly explained by the link between hardness and puroindoline contents. This link is in agreement with previous results which have shown a close structural identity between basic friabilins and puroindolines. Next, the effect of puroindolines in breadmaking was investigated by performing reconstitution experiments with two puroindoline‐free hard cultivars of opposite quality (Florence Aurore and Ecrin) as indicated in the screened wheat sample. Addition of 0.1% puroindolines to these flours drastically modified both the rheological properties of doughs and the structure of the bread crumb. Puroindolines are essential to the foaming properties of dough liquor, and a close relationship was found between the fine grain crumb provided by reconstituted flours with puroindolines and the fine structure of corresponding dough liquor foams. The effect of puroindolines on bread volume was mainly related to the rheological properties of wheat doughs.

Glycosidases and glycanases of wheat flour doughs.

AbstractWheat flour contains hydrolytic enzymes capable of reducing dramatically the viscosity of the aqueous solution obtained by high‐speed centrifugation of dough. Indirect evidence suggests this reduction in viscosity is largely due to the hydrolysis of glycosidic linkages in the non‐starch polysaccharides. Soluble proteins and starch contribute less to the viscosity of this dough liquor than do the flour gums. The glycanases in flour relatively rapidly hydrolyse the galactomannan, guaran and carboxymethylcellulose. Flour also contains a wide range of enzymes capable of hydrolysing nitrophenyl α‐ and β‐glucosides, α‐ and β‐galactosides, α‐ and β‐mannosides, α‐arabinoside, β‐fucoside and β‐xyloside. Both the glycanases and the glycosidases show pH optima within the range 4‐6 which covers the range normally encountered in dough.