Understanding the effect of emulsifiers on bread aeration during breadmaking

[EN] BACKGROUNDMuch research has been done to explain the action of emulsifiers during breadmaking, but there is still plenty unknown to elucidate their functionality despite their diverse chemical structure. The aim of the present study was to provide some light on the role of emulsifiers on air incorporation into the dough and gas bubbles progress during baking and their relationship with bread features. Emulsifiers like diacetyl tartaric acid ester of monoglycerides (DATEM), sodium stearoyl lactylate (SSL), distilled monoglyceride (DMG-45 and DMG-75), lecithin and polyglycerol esters of fatty acids (PGEF) were tested in very hydrated doughs. RESULTSEmulsifiers increase the maximum dough volume during proofing. Emulsifiers increase the number of bubbles incorporated during mixing, observing higher number of bubbles, particularly with PGEF. Major changes in dough occurred at 70K when bubble size augmented, becoming more heterogeneous. DMG-75 produced the biggest bubbles. As a consequence, emulsifiers tend to increase the number of gas cells with lower size in the bread crumb, but led to greater crumb firmness, which suggested different interactions between emulsifiers and gluten, affecting protein polymerization during baking. CONCLUSIONThe progress of the bubbles during baking allowed the differentiation of emulsifiers, which could explain their performance in breadmaking. (c) 2018 Society of Chemical IndustryAuthors acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2-1-R), the European Regional Development Fund (FEDER) and Generalitat Valenciana (Project Prometeo 2017/189).Garzon, R.; Hernando Hernando, MI.; Llorca Martínez, ME.; Molina Rosell, MC. (2018). Understanding the effect of emulsifiers on bread aeration during breadmaking. Journal of the Science of Food and Agriculture. 98(14):5494-5502. https://doi.org/10.1002/jsfa.9094S549455029814Rosell, C. M., & Garzon, R. (2015). 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Mécanismes d'alvéolation de pâtes à pain en cours de fermentation

In the framework of the European project Dream, whose objective is to develop realistic food models, our job is to determine the mechanisms of development of solid foams cereal, taken as a model of bakery products. To this end, the elongational properties of the starch / gluten matrix and the kinetics of stability and porosity of different doughs during fermentation were determined at the macroscopic scale. The cellular structure of these dough and their evolution were determined by in situ X-ray microtomography to clarify in particular the role of the volumic liquid fraction of the formulation. Starting from size distributions of gas cells and walls, the homogeneity of the structure is characterized by a critical thickness of walls (≈ 1μm), below which the cells are separated by liquid films. The dough after fermentation would thus be a three-phase medium : viscoelastic matrix / cell gas / liquid phase. Dough liquor, as a model of this 3rd phase, is extracted, and its composition, its foaming and rheological properties are determined, suggesting the role of the surface tension and the formation of polysaccharides- proteins complexes at interfaces. The contributions of the different levels of organization of the dough are integrated by defining a capillary number ≈ 10-2), to interpret all mechanisms. Phenomenological models of these mechanisms have been built which leads to a book of knowledge, to be tested for the study of the addition of fibers, nutritional target of bakery products.Dans le cadre du projet européen Dream, dont l'objectif est de développer des modèles d'aliments réalistes, notre travail consiste à déterminer les mécanismes d'élaboration de mousses solides céréalières, prises comme modèle de produits de panification. A cette fin, les propriétés élongationnelles de la matrice amidon/gluten et les cinétiques de porosité et de stabilité ont été déterminées, à l'échelle macroscopique, pour différentes pâtes à pain, en cours de fermentation. La structure alvéolaire de ces pâtons et leur évolution ont été déterminées in situ par microtomographie aux rayons X, pour préciser notamment le rôle de la fraction volumique liquide de la formulation. À partir des distributions de taille d'alvéoles et de parois, l'homogénéité de la structure est caractérisée par une épaisseur critique de parois (≈ 1μm), en deçà de laquelle les alvéoles seraient séparées par des films liquides. La pâte en fin de fermentation serait donc un milieu triphasique : matrice viscoélastique /alvéoles gazeuses/phase liquide. La liqueur de pâte, prise comme modèle de cette 3eme phase, est extraite, et sa composition ainsi que ses propriétés rhéologiques et moussantes sont déterminées, suggérant le rôle de la tension superficielle et la formation de complexes polysaccharides-protéines aux interfaces. Les contributions aux différents niveaux d'organisation de la pâte sont intégrées par la définition d'un nombre capillaire (≈ 10-2), afin d'interpréter l'ensemble des mécanismes. Ceux-ci ont fait l'objet d'une modélisation phénoménologique, qui conduit à un livre de connaissances, à éprouver pour l'étude de l'addition de fibres, cible nutritionnelle des produits de panification

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

International audienceDough 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 s(n), 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

Growth and setting of gas bubbles in a viscoelastic matrix imaged by X-ray microtomography: the evolution of cellular structures in fermenting wheat flour dough

International audienceX-ray tomography is a relevant technique for the dynamic follow-up of gas bubbles in an opaque viscoelastic matrix, especially using image analysis. It has been applied here to pieces of fermenting wheat flour dough of various compositions, at two different voxel sizes (15 and 5 mm). The resulting evolution of the main cellular features shows that the creation of cellular structures follows two regimes that are defined by a characteristic time of connectivity, t(c) [30 and 80 min]: first (t = t(c)) they become connected since the percolation of the gas phase is limited by liquid films. During the first regime, bubbles can be tracked and the local strain rate can be measured. Its values (10(-4)-5 x 10(-4) s(-1)) are in agreement with those computed from dough viscosity and internal gas pressure, both of which depend on the composition. For higher porosity, P = 0.64 in our case, and thus occurring in the second regime, different cellular structures are obtained and XRT images show deformed gas cells that display complex shapes. The comparison of these images with confocal laser scanning microscopy images suggests the presence of liquid films that separate these cells. The dough can therefore be seen as a three-phase medium: viscoelastic matrix/gas cell/liquid phase. The contributions of the different levels of matter organization can be integrated by defining a capillary number (C-a(*) = 0.1-1) that makes it possible to predict the macroscopic dough behavior

Integration of basic knowledge models for the simulation of cereal foods processing and properties

International audienceCereal processing (breadmaking, extrusion, pasting, etc.) covers a range of mechanisms that, despite their diversity, can be often reduced to a succession of two core phenomena: (1) the transition from a divided solid medium (the flour) to a continuous one through hydration, mechanical, biochemical, and thermal actions and (2) the expansion of a continuous matrix toward a porous structure as a result of the growth of bubble nuclei either by yeast fermentation or by water vaporization after a sudden pressure drop. Modeling them is critical for the domain, but can be quite challenging to address with mechanistic approaches relying on partial differential equations. In this chapter we present alternative approaches through basic knowledge models (BKM) that integrate scientific and expert knowledge, and possess operational interest for domain specialists. Using these BKMs, simulations of two cereal foods processes, extrusion and breadmaking, are provided by focusing on the two core phenomena. To support the use by non-specialists, these BKMs are implemented as computer tools, a Knowledge-Based System developed for the modeling of the flour mixing operation or Ludovic®, a simulation software for twin screw extrusion. They can be applied to a wide domain of compositions, provided that the data on product rheological properties are available. Finally, it is stated that the use of such systems can help food engineers to design cereal food products and predict their texture properties