Dough Liquor Research Articles

Elucidating the gas cell stabilization mechanism of buckwheat-wheat steamed bread induced by transglutaminase: A focus on the foaming and air-water interfacial properties of dough liquor

This work investigated the improvement mechanism of transglutaminase (TG) on the buckwheat-wheat steamed bread qualities from the view of protein structural, foaming and air-water interfacial properties of dough liquor (DL). TG reduced the hardness, ameliorated the crumb structure and enhanced the specific volume of buckwheat-wheat steamed bread by up to 9.0%. The DL yield, protein and water recovery were notably increased as the TG concentration increased to 0.2 U/g, then decreased with the higher TG concentrations. The low TG concentrations (<0.2 U/g) increased the protein molecular weight, and decreased the protein hydrophobicity, free amino and sulfhydryl groups content of DL. The high TG concentrations (>0.2 U/g) tended to induce both protein intermolecular and intramolecular cross-linking, which reduced the average particle size from 9.6 to 4.3 μm as the TG concentration increased from 0.2 to 1.0 U/g. TG markedly improved the foaming capacity and foam stability, decreased the surface tension and strengthened the interfacial films by enhancing the viscoelasticity modulus of buckwheat-wheat DL interfacial protein films. The topography of the air-water interfacial layer revealed that the TG-induced protein cross-linking led to a more homogeneous and denser topographical structure. This work will provide fresh insight into the effects of TG-induced protein cross-linking on gas cell stabilization and relate them to the buckwheat-wheat steamed bread quality properties.

Alkali-Induced Protein Structural, Foaming, and Air-Water Interfacial Property Changes and Quantitative Proteomic Analysis of Buckwheat Sourdough Liquor.

In this study, the protein structural, foaming, and air-water interfacial properties in dough liquor (DL) ultracentrifugated from buckwheat sourdough with different concentrations of an alkali (1.0-2.5% of sodium bicarbonate) were investigated. Results showed that the alkali led to the cross-linking of protein disulfide bonds through the oxidation of free sulfhydryl groups in DL. The alterations in protein secondary and tertiary structures revealed that the alkali caused the proteins in DL to fold, decreased the hydrophobicity, and led to a less flexible but compact structure. The alkali accelerated the diffusion of proteins and decreased the surface tension of DL. In addition, the alkali notably improved the foam stability by up to 34.08% at 2.5% concentration, mainly by increasing the net charge, reducing the bubble size, and strengthening the viscoelasticity of interfacial protein films. Quantitative proteomic analysis showed that histones and puroindolines of wheat and 13S globulin of buckwheat were closely related to the changes in the alkali-induced foaming properties. This study sheds light on the mechanism of alkali-induced improvement in gas cell stabilization and the buckwheat sourdough steamed bread quality from the aspect of the liquid lamella.

Impact of roasted oat flour on the gas cell structure of steamed oat cake and its underlying mechanism

Roasting (or called stir-frying) can modify the properties of oat flour and improve the poor quality of steamed oat cake, especially uneven gas cell and high hardness, but the underlying mechanism remains unclear. The properties of protein-starch network matrix of oat dough (made by roasted oat flours with gelatinization degrees of 30%, 50% 70% and 90%) before and after steaming were investigated, as well as the air/water interfacial characteristics of oat dough liquor. Results revealed that adding roasted oat flour with moderate gelatinization degree to the raw oat flour (ROF) could significantly improve the quality of steamed oat cakes, and their average pore size and specific volume reached the corresponded maximum values when roasted oat flour with gelatinization degree of 50% (G50) was added, which were 1.97 mm and 2.56 mL/g, respectively. Roasted oat flour with moderately gelatinization could not only facilitate the formation of protein polymers by promoting disulfide cross-linking of larger monomer proteins in both raw and steamed oat dough, but also induce the conversion of random coil to α-helix and β-sheets structure, resulting in an ordered protein secondary structure. Meanwhile, the improvement of short-range molecular order structure of starch in oat dough was observed for ROF/G50（w/w = 1:1）sample (RG50). Additionally, compared to ROF, RG50 sample possessed the strongest foaming stability, which increased from 32.70% to 61.43%. In conclusion, the quality enhancement of steamed oat cake can be attributed to the combined effects of changes in the protein-starch matrix and the thin liquid film induced by moderately roasted oat flour.

Unraveling the impacts of fermentation methods on the protein structural, foaming and air-water interfacial properties of buckwheat steamed bread dough liquor

Liquid lamella has crucial impacts on stabilizing gas cells and buckwheat steamed bread (BSB) quality due to the high fiber content and lack of gluten protein in buckwheat. The liquid lamella was collected by ultracentrifugation as the dough liquor (DL). This study explored the composition, foaming and interfacial properties of DL from lactic acid bacteria (LAB), yeast, LAB and yeast cooperate (LAB-yeast), and chemical acidified and yeast (CA-yeast) fermented buckwheat dough, as well as the unfermented buckwheat dough. Compared with the unfermented dough, the DL yield of LAB-yeast, yeast, and CA-yeast fermented dough decreased by 4.09%, 3.93%, and 7.67%, respectively. The protein molecular weight and surface hydrophobicity of DL were dramatically reduced by LAB, LAB-yeast, and CA-yeast fermentation as compared to unfermented DL. Among all DL samples, the unfermented and yeast DL showed the highest protein surface hydrophobicity and surface activity, resulting in the greatest foam stability. The protein in CA-yeast DL displayed the fastest interface diffusion because its DL had the highest amount of low molecular weight protein, the lowest viscosity and protein content. Compared with the unfermented dough, the LAB and LAB-yeast fermentation decreased, while the CA-yeast fermentation increased the strain hardening index (SHI) of the dough. This enhanced strain hardening behavior contributed to a decrease in the average cell area and an increase in cell density, making the crumb structure of CA-yeast fermented BSB homogeneous and dense.

The role of lipids in determining the gas cell structure of gluten-free steamed oat cake

The stabilization of gas cells is crucial to obtain cake or bread products with a homogeneous crumb and is mainly depends on the proteins, starches, and lipids. Oats, in particular, are known for their high lipid content compared to other grains. However, the specific contribution of oat lipids to the gas chamber structure in gluten-free steamed oat cake is still unclear. Hence, to elucidate the potential mechanism involved, this study aimed to investigate the steaming characteristics of oat dough, as well as the protein-starch network matrix (including protein aggregation and structural properties), and the air/water interfacial characteristics (including foaming and surface tension properties) of oat dough liquor subjected to different defatting treatments. Results showed that by moderately removing lipids from samples (particularly ROF-D3 with 2.91% lipid content), gas retention ability, cell area fraction, and specific volume of the steamed oat cake were enhanced, which were 93.30 mL/100 mL, 36.27%, and 2.72 mL/g, respectively. Weak protein aggregation and an ordered protein secondary structure corresponding to a more open and stable protein network structure were observed in the ROF-D3 sample caused by moderate lipid removal. In addition, moderate removal of lipids obviously increased the extraction yield of oat dough liquor, in which lipid was evidently the dominant component. Compared to the ROF-D1 sample, the enhanced quality of the ROF-D3 sample can be attributed to the strongest foam stability and the increased air-water interface surface tension.

Exploring the role of the liquid phase in dough made with sprouted wheat wholemeal in bread production

To unravel the effect of sprouted wheat wholemeal (SWW) on bread characteristics, baking performance of SWW and commercial white bread wheat flour (BWF) blends was investigated. The inclusion of soft or hard SWW increased the total monosaccharide and reducing sugar concentrations, α-amylase and proteolytic activity in dough liquor (DL) relative to what was found in DL obtained from dough prepared with only BWF or unsprouted wheat wholemeal (UWW). The apparent bulk viscosity and air-water interfacial rheological properties of DL were changed upon inclusion of UWW and SWW in the recipes, likely reflecting changes in the DL arabinoxylan and protein content, while the surface tension of dough liquor was not altered by inclusion of UWW or SWW. The interfacial elastic modulus correlated positively with the protein concentration of DL, while bread loaf volume was negatively correlated with DL protein concentration and air-water interfacial elastic and viscous moduli. DL bulk viscosity, conversely, had a more complex relation to bread loaf volume. Besides affecting the DL properties, sprouting also altered the gluten aggregation properties. More research is needed to identify the fine interplay between all these factors determining breadmaking performance.

The influence of xylanase and thermal treatment on the composition and interfacial rheology properties of whole wheat dough liquor

SummaryThe dough liquor (DL) centrifuged from dough played an important role in determining the gas cell stability during dough making, and the adding of xylanase (XYL) in the dough could efficiently increase the stability of DL foam, especially at 60 °C. In this work, we prepared whole wheat dough added with different dosages of XYL and extract the DL. The components especially proteins in DL and their interaction mechanism and interfacial rheology properties at the air–water interface were studied. The proteins formed protein aggregates (&gt;150 kDa) at 60 °C. After XYL treatment, DL solution exhibited higher protein surface hydrophobicity and surface pressure. And the equilibrium surface pressure of DL varied between 23 and 28 mN m−1. At 25 °C, the interfacial dilatational modulus increased by 26.77% and 14.22% compared with control, respectively. And the XYL can improve the interface shear strength both for the unheated and heated DL solutions. These findings showed that XYL might improve the ability of DL constituents to stabilise the air–water interface to contribute to the stability of gas cells in the dough. The obtained results have provided a theoretical basis for improving the gas cell stability by changing the properties of whole wheat DL with the addition of XYL.

Gas cell stabilization by aqueous-phase constituents during bread production from wheat and rye dough and oat batter: Dough or batter liquor as model system.

Proper gas cell stability during fermentation and baking is essential to obtain high-quality bread. Gas cells in wheat dough are stabilized by the gluten network formed during kneading and, from the moment this network locally ruptures, by liquid films containing nonstarch polysaccharides (NSPs) and surface-active proteins and lipids. Dough liquor (DL), the supernatant after ultracentrifugation of dough, is a model system for these liquid films and has been extensively studied mostly in the context of wheat bread making. Nonwheat breads are often of lower quality (loaf volume and crumb structure) than wheat breads because their doughs/batters lack a viscoelastic wheat gluten network. Therefore, gas cell stabilization by liquid film constituents may be more important in nonwheat than in wheat bread making. This manuscript aims to review the knowledge on DL/batter liquor (BL) and its relevance for studying gas cell stabilization in wheat and nonwheat (rye and oat) bread making. To this end, the unit operations in wheat, rye, and oat bread making are described with emphasis on gas incorporation and gas cell (de)stabilization. A discussion of the knowledge on the recoveries and chemical structures of proteins, lipids, and NSPs in DLs/BLs is provided and key findings of studies dealing with foaming and air-water interfacial properties of DL/BL are discussed. Next, the extent to which DL/BL functionality can be related to bread properties is addressed. Finally, the extent to which DL/BL is a representative model system for the aqueous phase of dough/batter is discussed and related to knowledge gaps and further research opportunities.

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.

Chemical stability and reaction kinetics of thiamine mononitrate in the aqueous phase of bread dough

Thiamine is a water-soluble essential micronutrient, and grains are the main source of thiamine in the human diet. Refining processes reduce thiamine content; therefore, many flours are enriched with thiamine. Further processes, such as heating (baking), destabilize thiamine. In doughs, thiamine partitions into the aqueous phase (dough liquor). The objective of this study was to document temperature effects on thiamine degradation reaction kinetics in dough liquor. Two concentrations of thiamine mononitrate (1 and 20 mg/mL) were added to dough liquor (the supernatant of centrifuged bread dough) and control solutions (water and pH 6-adjusted water). Samples were stored at controlled temperatures (25, 40, 60, 70, and 80 °C) for up to 6 months, and thiamine degradation was quantified over time using high-performance liquid chromatography. Thiamine degradation kinetics, including the observed reaction rate constant (kobs) and activation energy (Ea) of degradation, were calculated. Dough liquor ingredients stabilized thiamine in most cases when compared to the pH 6 control solutions, especially in the samples containing more thiamine. Thiamine degradation in dough liquor generally followed similar trends to those in the controls: thiamine degraded more quickly in the 20 mg/mL solutions than in 1 mg/mL solutions (with one exception), and increasing temperature led to increased thiamine degradation. However, kobs ranged from 0.0019–0.22 days−1 in dough liquor and 0.0003–0.46 in control solutions, with differences attributed to interactions with components in the dough liquor. The Ea of thiamine degradation was ~90 kJ/mol in the control samples regardless of vitamin concentration but differed between vitamin concentrations in the dough liquor (95 and 60 kJ/mol in 1 and 20 mg/mL solutions, respectively), indicating that a different degradation pathway may have occurred in dough liquor. The different thiamine stability trends in dough liquor compared to control solutions indicate that food formulation has a substantial impact on the chemical behaviors of thiamine.

Genetic variation in wheat grain quality is associated with differences in the galactolipid content of flour and the gas bubble properties of dough liquor

Lipids affect the quality of wheat flour for breadmaking. One possible mechanism is stabilization of the gas cells which are formed during dough mixing and expanded during fermentation, leading to a greater loaf volume and evenness of texture. We therefore compared the lipidomic profiles of flour and dough liquor fractions (which contain surface-active components present at the gas bubble interface) from two sets of wheat lines differing in allelic variation at a QTL for loaf volume. Analyses of fractions from three field trials showed consistent increases in the contents of galactolipids (monogalactosyl diglyceride and digalactosyl diglyceride) in flour and dough liquor of the lines with the increasing (good quality) allele. Biophysical analysis showed that this was associated with greater elasticity of the dough liquor fraction. This is consistent with published studies reporting a relationship between galactolipids and breadmaking quality and suggests a mechanism of action for the QTL.

Composition and foam properties of whole wheat dough liquor as affected by xylanase and glucose oxidase

Xylanase (XYL) and glucose oxidase (GOX) have been applied to improve the crumb structure of whole wheat buns. However, their effects on the constituents dissolved in the dough liquor (DL), which supposedly contributed to gas cell stabilization and crumb structure, have not been elucidated. In this study, we aimed to unravel the effects of these enzymes on the protein and arabinoxylan contents, DL yields, bulk viscosity, as well as foaming properties. DL was first separated through ultracentrifugation from whole wheat dough prior treated by XYL and GOX. The results indicated that XYL and GOX treatment increased the DL yields. Moreover, while XYL increased the water extractable arabinoxylan content, GOX increased the protein level in the DL. The free sulfhydryl groups of soluble proteins declined significantly in the presence of GOX. Moreover, GOX might have catalyzed the formation of large protein aggregates and protein-polysaccharide complexes. Furthermore, while the foaming capacity of DL increased only in the presence of XYL, the foam stability was increased by both XYL and GOX, especially under heat treatment. The present research might help to understand the mechanism of crumb structure improvement of whole wheat buns by XYL/GOX treatment from the view of their effects on the DL.

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

Bread is mainly made from wheat but also from other cereals such as rye and oats. We here report on the role of dough liquor (DL) proteins and lipids in determining the stability of gas cell air-water (A-W) interfaces in wheat, rye, and oat bread making. Surprisingly, most lipids in DLs of these cereals are nonpolar. Their main polar DL lipids are phospholipids. Lipids at wheat and rye DL stabilized A-W interfaces impair interactions between its proteins, as reflected by an increased A-W interfacial shear viscosity of the adsorbed film upon defatting. In contrast, removing most lipids from oat DL pronouncedly increased the A-W interface surface tension, demonstrating that lipids are the prominent adsorbed species.

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.

Relating the composition and air/water interfacial properties of wheat, rye, barley, and oat dough liquor

Gas cell stabilization in dough by its aqueous phase constituents is arguably more important in non-wheat than in wheat dough due to weaker protein networks in the former. Dough liquor (DL), a model for the dough aqueous phase, was isolated from fermented wheat, rye, barley, and oat doughs by ultracentrifugation. DL composition (protein, lipid, arabinoxylan, β-glucan) and air/water interfacial functionality [foaming, viscosity, surface tension, surface dilatational modulus (E)] were related to bread quality. Poor foaming and low E of wheat DL were ascribed to lipids and proteins co-occurring at the interface. Nonetheless, the presence of a gluten network resulted in high-quality wheaten breads. Homogeneous and heterogeneous crumb structures of rye and barley breads, respectively, were attributed to high and low E values of their respective DLs. High lipid content and low surface tension of oat DL indicated a lipid-dominated interface, which may explain the heterogeneous crumb structure of oat breads.

Intrinsic wheat lipid composition effects the interfacial and foaming properties of dough liquor

Doughs were prepared from a single variety breadmaking flour (cv. Hereward), from three successive harvests (years; 2011, 2012 and 2013). A preparation of the aqueous phase from dough, known as dough liquor (DL), was prepared by ultracentrifugation and its physico-chemical properties were investigated. Surface tension and interfacial rheology, showed that the interface of DL was lipid-dominated and that 2013 DL had a different type of interface to 2011 and 2012 DL. This data was consistent with the improved foam stability observed for 2013 DL and with the types of lipids identified. All foams collapsed quickly, but the most stable foam was from 2013 DL with 89.2% loss in foam, followed by 2011 DL with 91.7% loss and 2012 had the least stable foam with a loss of 92.5% of the foam structure. Glycolipids (DGDG and MGDG) were enriched in 2013 DL, and were also present in DL foam, contributing towards improved stability. Neutral lipids, such as FFAs, were enriched in DL foams contributing towards instability and rapid foam collapse. Baking trials using 2012 and 2013 flour, showed increased loaf volumes and gas bubble diameter in 2013 bread compared to 2012 bread, highlighting the potential impact that surface active polar lipids, enriched in the aqueous phase of dough, could have on improving breadmaking quality.

Breast Milk IgA Levels in the Old Order Mennonite Vs. City Mothers

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.

Native and enzymatically modified wheat (Triticum aestivum L.) endogenous lipids in bread making: A focus on gas cell stabilization mechanisms

Lipopan F and Lecitase Ultra lipases were used in straight dough bread making to study how wheat lipids affect bread loaf volume (LV) and crumb structure setting. Lipase effects on LV were dose and dough piece weight dependent. The bread quality improving mechanisms exerted by endogenous lipids were studied in terms of gluten network strengthening, which indirectly stabilizes gas cells, and in terms of direct interfacial gas cell stabilization. Unlike diacetyl tartaric esters of mono- and diacylglycerols (DATEM, used as control), lipase use did not impact dough extensibility. The effect on dough extensibility was therefore related to its lipid composition at the start of mixing. Both lipases and DATEM strongly increase the levels of polar lipids in dough liquor and their availability for and potential accumulation at gas cell interfaces. Lipases form lysolipids that emulsify other lipids. We speculate that DATEM competes with (endogenous) polar lipids for interacting with gluten proteins.

Foaming and rheological properties of the liquid phase extracted from wheat flour dough

Dough liquor (DL) is considered as a good model of bread dough liquid phase which plays an important role in alveolar structure creation. In this work, DL was extracted from dough pieces of various contents (g for 100 g flour) of water (55–70), sugar (0–15), rapeseed oil (0–10) and bran (0–20). The extraction yield of DL was 5.0 ± 2.4% and its dry matter content varied between 10.8 and 27.2% of total DL mass. Its composition has been determined in terms of lipids content (≤0.08 mg/mL), polysaccharides, mostly arabinoxylans (0.9–4.7 mg/mL), arabinogalactan-proteins (AGP) and soluble proteins (20.7–38.0 mg/mL). The rheological properties (bulk and surface) of fresh DL, and foaming properties of diluted DL (1/10), were determined using cone-plate rheometry, pendant drop method and Foamscan device, respectively. DL behaved like a macromolecular solution, displaying a slight shear-thinning behavior with an apparent viscosity varying between 0.03 and 0.6 Pa sn, at shear rate 10 s−1. Its surface tension varied between 35 and 45 mN/m. Its adsorption kinetics, governed by protein diffusion to the interface, followed two regimes, the first one depending on sugar content, and the second one on AGP content. Drainage and foam stability kinetics were influenced by neutral sugars, probably through the impact of glucose and mannose on DL viscosity. The understanding of the mechanisms of fermented dough stability could be improved by taking the results of DL surface tension into account.

Wheat (Triticum aestivum L.) puroindoline functionality in bread making and its impact on bread quality

Wheat puroindolines (PINs) spontaneously adsorb at air/water interfaces and show excellent foaming properties. They can positively impact bread quality, in which the formation of stable foam is important for product quality. The impact of endogenous PINs on bread quality was studied by preparing gluten–starch blends from isolated gluten and starch fractions with different PIN levels, which allowed largely retaining the interaction between PINs and flour components. Our results indicate that blends with high PIN levels yielded more homogeneous crumb structures with fine gas cells than bread made with blends containing medium or low PIN levels. However, the mechanism by which PINs exert this crumb improving effect is not clear. Varying PIN levels impacted neither dough extensibility nor did it result in different PIN levels in dough liquor. Lipid removal yielded bread with a less homogeneous crumb gas cell distribution, indicating that lipids also are required to obtain good crumb structure.