Dough extensional properties obtained from 14 wheat flours hydrated at 50% (/flour weight) were assessed by the empirical test of Alveograph, a bubble inflation test, and by the rheometric test of ...uniaxial compression in lubricated conditions (LSF) at large deformations. In baking industry, comparison between flours is based on several parameters (
n
≥ 5) defined from the alveogram, which is the time variations of pressure inside dough. In this study, the alveogram is converted into a stress-strain curve (
σ
=
f
(
ε
b
)). Then, from this curve, the extensional behavior coefficient of the flours, assessed by the consistency
k
0
, is fitted between 0 ≤ ε
b
≤ 1.5, assuming
ε
b
˙
= 0.25 s
−1
(
R
2
= 0.99 ± 0.01 for 14 flours). The flow index (
n
= 0.36) and strain hardening index (SHI = 1.73) are kept constant. The model is validated by comparing the stress values calculated from the alveogram to those measured in LSF for wheat flour doughs hydrated at 50% (
R
2
= 0.91) at
ε
b
= 1 and 0.25.10
−2
<
ε
b
˙
< 2.5 s
−1
. Therefore, the Alveograph, which allows classifying flours according to several dough stretching properties, also provides access to the model of dough extensional behavior.
Graphical abstract
Determining dough extensional properties for alveograph test and validating by comparison with resutls obtained by LSF
Heteroxylans (HX) from vitreous and floury parts of maize endosperm were isolated. Structural analysis showed a xylan backbone with few unsubstituted xylose residues (<9%) demonstrating the high ...content in side chains in both fractions. HX from floury endosperm contained more arabinose and galactose than vitreous HX. The mono-substitution rate was 15% higher in the vitreous endosperm HX. Similar amounts of uronic acids were present in both fractions (~7% DM). Galactose in the floury endosperm HX was present exclusively in terminal position. A xylanase preparation solubilized more material from floury (40.5%) than from vitreous endosperm cell walls (15%). This could be a consequence of the structural differences between the two fractions and/or of the impact of structure on the interaction abilities of these fractions with other cell wall polysaccharides.
Our study advances the understanding of cell wall polysaccharides in maize endosperm and their role in enzymatic susceptibility of maize grain.
•Heteroxylans (HX) from vitreous and floury endosperm of maize were characterized.•The floury endosperm contains more cell wall components than the vitreous one.•Vitreous HX contains 15% more mono-substituted xylose than floury HX.•Xylanases solubilized ~2.5 more matter from floury than from vitreous cell walls.•The results will allow improving the enzymatic preparations used in animal feeding.
Arabinoxylans (AX) and (1→3),(1→4)-β-glucans (BG) are the major components of wheat grain cell walls. Although incompletely described at the molecular level, it is known that the chemical and ...distributional heterogeneity of these compounds impacts the quality and use of wheat. In this work, an emerging technique based on MALDI mass spectrometry imaging (MSI) was employed to map variations in the quantity, localization, and structure of these polysaccharides in the endosperm during wheat maturation. MALDI MSI couples detailed structural information with the spatial localization observed at the micrometer scale. The enzymic hydrolysis of AX and BG was performed directly on the grain sections, resulting in the efficient formation of smaller oligosaccharides that are easily measurable through MS, with no relocation across the grain. The relative quantification of the generated oligosaccharides was achieved. The method was validated by confirming data previously obtained using other analytical techniques. Furthermore, in situ analysis of grain cell walls through MSI revealed previously undetectable intense acetylation of AX in young compared to mature grains, together with findings concerning the feruloylation of AX and different structural features of BG. These results provide new insights into the physiological roles of these polysaccharides in cell walls and the specificity of the hydrolytic enzymes involved.
A major challenge faced when studying the “structure-degradability” interaction of native starch is deciphering the interdependency between different structural levels, especially when experimental ...conditions limit the number of samples. To tackle this challenge, 224 wheat starches from a 4-way multiparent advanced generation inter-cross population were screened for structural features and degradation profiles by porcine pancreatic α-amylase. A hierarchical clustering on principal components (HCPC) were used as multifactorial analysis to explore the data structure. The degradation procedure was proved to be robust and sensible enough to screen a large collection of starches. The HCPC highlighted the combined effects of granule size distribution (GSD), amylopectin chain length distribution (CLD), amylose content and endogenous α-amylase activity on degradation kinetics. Especially the GSD and amylopectin CLD showed high co-occurrences with specific hydrolysis profiles. These findings provide an innovative screening method and structural factors to be primarily considered for wheat starch selection in breeding programs.
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•Distribution of polysaccharides during Brachypodium grain development.•Fine structure of arabinoxylans varies according to tissue and grain development.•Amazing distribution of polysaccharides ...highlighted into the testa of Brachypodium grain.
Brachypodium distachyon (Brachypodium) is now well considered as being a suitable plant model for studying temperate cereal crops. Its cell walls are phylogenetically intermediate between rice and poaceae, with a greater proximity to these latter. By microscopic and biochemical approaches, this work gives an overview of the temporal and spatial distribution of cell wall polysaccharides in the grain of Brachypodium from the end of the cellularization step to the maturation of grain. Variation in arabinoxylan chemical structure and distribution were demonstrated according to development and different grain tissues. In particular, the kinetic of arabinoxylan feruloylation was shown occuring later in the aleurone layers compared to storage endosperm. Mixed linked β-glucan was detected in whole the tissues of Brachypodium grain even at late stage of development. Cellulose was found in both the storage endosperm and the outer layers. Homogalacturonan and rhamnogalacturonan I epitopes were differentially distributed within the grain tissues. LM5 galactan epitope was restricted to the aleurone layers contrary to LM6 arabinan epitope which was detected in the whole endosperm. A massive deposition of highly methylated homogalacturonans in vesicular bodies was observed underneath the cell wall of the testa t2 layer at early stage of development. At maturity, low-methylated homogalacturonans totally fulfilled the lumen of the t2 cell layer, suggesting pectin remodeling during grain development. Xyloglucans were only detected in the cuticle above the testa early in the development of the grain while feruloylated arabinoxylans were preferentially deposited into the cell wall of t1 layer. Indeed, the circumscribed distribution of some of the cell wall polysaccharides raises questions about their role in grain development and physiology.
Wheat flour doughs were elaborated with wheat-bran in various contents, up to 20%, and particle sizes of fractions, in order to study the specific role of rheological properties in processing high ...fibre breads. The addition of wheat bran, especially more than 10%, decreased the specific mechanical energy developed by the mixer, which was attributed to a deficient formation of the gluten network. It increased the elongational viscosity of the dough, measured by biaxial extension tests, likely through a solid particles effect. These changes explained the lower increase of porosity during proofing, assessed by digital camera and 2D image analysis. The loss of dough stability was rather attributed to the destabilizing effect of bran particles on the films separating gas bubbles. The resulting changes of bread texture, determined by image analysis and mechanical testing of breads, including crust and crumb, were governed by bread density, which was established at the end of proofing. These results help to understand the impact of wheat bran on dough rheological properties in order to design French breads with increased fibre content.
•Bran addition led to lower mixing energy but higher elongational viscosity of dough.•Higher elongational viscosity decreased expansion of bran added dough during proofing.•Lower proofing expansion led to larger bread densities of fibres enriched breads.•Firmer texture of fibres enriched breads was mainly due to increased density.•For same overall fibre level, varying bran size reduces negative effects on texture.
Rheology of wheat flour dough at mixing Della Valle, Guy; Dufour, Maude; Hugon, Florence ...
Current opinion in food science,
October 2022, 2022-10-00, 2022-10, Letnik:
47
Journal Article
Recenzirano
Odprti dostop
The baking industry performs common technological (empirical) tests. Unfortunately, the results hardly predict the dough behavior online. This paper first reviews the most common methods to assess ...the rheological properties of the dough, including empirical tests, small and large deformations methods. A second section describes the relations between rheological properties and dough behavior at the critical step of dough mixing. We put forward a tentative interpretation of these relations based on dough structural changes supported by results from imaging or spectroscopic methods. Finally, a review of simple models consistent with the physical understanding of the dough behavior is presented as tools that scientist and engineers can use to interpret experimental data, perform system analysis and anticipate the product properties.
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•The extensional behavior of dough can be assessed by various methods.•The power curve measured during mixing can be used to assess rheological behavior.•NMR spectroscopy opens prospects to link water distribution to dough rheology.•Modeling dough mixing contributes to integrate rheological properties.
Several fractions of wheat fibres were isolated from starchy endosperm, aleurone layer and bran, and characterized for their hydration properties and arabinoxylans (AX) content. The influence of ...their addition, up to 10%, to standard flour was studied through mixing tests, and rheological tests at small and large deformations. The effect of insoluble AX on dough development was accounted for by their capacity to retain water, whatever their origin and percentage of addition. The addition of insoluble AX increased the viscoelastic plateau modulus. The addition of soluble and insoluble AX to the dough did not modify the overall dough flow behaviour in shear, characterized by a Newtonian plateau at low shear rates followed by shear-thinning behaviour at larger shear rates. This behaviour could be fitted by the Cross model. The addition of water soluble AX modified the Newtonian viscosity value. Conversely, the addition of insoluble ones increased dough consistency, probably through a filler-like effect in the dough matrix.
•Mannan-enriched extracts were obtained from wheat endosperm and characterized.•In wheat endosperm, mannan is made of short unsubstituted chains of mannose.•Despite its linear structure, wheat mannan ...is (partly) water soluble.•No interaction between wheat mannan and other cell wall components were detected.
In wheat endosperm, mannan, is poorly documented. Nevertheless, this hemicellulosic polysaccharide might have a determinant role in wheat grain development since, in Arabidopsis thaliana, mutants with a reduced amount of mannan show an altered seed development. In order to gain knowledge about mannan in wheat, we have determined its biochemical structure in wheat endosperm where mannose content is about 0.2% (dry weight basis). We developed a method of enzymatic fingerprinting and isolated mannan-enriched fractions to decipher its fine structure. Although it is widely accepted that the class of mannan present in grass cell walls is glucomannan, our data indicate that, in wheat endosperm, this hemicellulose is only represented by short unsubstituted chains of 1,4 linked D-mannose residues and is slightly acetylated. Our study provides information regarding the interactions of mannan with other cell wall components and help to progress towards the understanding of monocot cell wall architecture and the mannan synthesis in wheat endosperm.
This study was to investigate the distribution of water and arabinoxylan structures in growing wheat grain using two complementary imaging techniques, magnetic resonance microimaging (μMRI) and mass ...spectrometry imaging (MSI). μMRI showed an inhomogeneous water distribution, particularly at early stages. This heterogeneity revealed histological differences that corresponded, within the limits of resolution of μMRI, to tissues with specific physiological functions, including the vascular bundles, the cavity and the endosperm periphery. All of these tissues had a higher water content than the central endosperm. MSI revealed distinct xylan structures in these regions with high levels of Araf substitution around the cavity and acetylated xylans concentrated at the endosperm periphery. For the first time, acetylation and Araf substitution of arabinoxylans were found by image processing to spatially correlate with water distribution in planta. Acetylation and Araf substitution of xylans, which alter chain-chain interactions and increase wall porosity, decreased as the grain matured.
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