Structuration de pâtes de blé fortement hydratées par un traitement thermomécanique pour la production d’un matériau céréalier 

Structuration de pâtes de blé fortement hydratées par un traitement thermomécanique pour la production d’un matériau céréalier 

Nous avons pu voir dans l’état de l’art que les mécanismes de structuration des pâtes de blé soumises à un traitement thermomécanique sont relativement peu étudiés, ce traitement étant très marginalement utilisé dans la fabrication des produits céréaliers. Dans le contexte de ce projet, ce traitement apparait pertinent pour modifier la viscosité de la pâte de blé et cibler des propriétés rhéologiques d’intérêt pour l’impression 3D.

L’objectif de ce chapitre est d’étudier la structuration de pâtes de blé de teneur en eau et composition variée par un procédé thermomécanique (à teneur en eau constante) et la compatibilité des pâtes transformées pour l’impression 3D (Figure 42). Les résultats de ce chapitre ont donné lieu à un article en cours de soumission présenté ci-dessous. Figure 42 : Démarche de recherche pour la production d’un matériau céréalier composé de farine de blé et d’eau (avec et sans sucre et /ou huile) obtenu par le traitement thermomécanique d’une pâte de blé. 1

Structuration de pâtes fortement hydratées par traitement thermomécanique

Structuration of wheat dough by thermomechanical process, from liquid food to 3D-printable food material Laurena Masbernat a, Sophie Berland a, Cassandre Leverrier a, Camille Michon a, Giana Almeida a a Université Paris-Saclay, INRAE, AgroParisTech, UMR SayFood, 91300, Massy, France. Corresponding authors: giana.perre@agroparistech.fr Abstract The printability of food materials depends on the rheology of the food under shearing when extruded and at rest after extrusion.

Piloting the microstructure of food to give the rheological properties compatible with 3D extrusion printing is a great challenge. Microstructure, rheology and printability of wheat-flour based materials with various contents in flour, sugar, oil and water were studied. Materials were obtained by heating and shearing doughs with moisture content above 55% (wb). The processed doughs were structured by close-packed particles made of swollen gelatinized starch granules embedded in a denatured glutenin and gliadine network acting as a glue.

These materials were easily extruded in cohesive layers by a 3D food printer and formed stable objects with accurate shape dimensions. Water/Flour ratio played a crucial role on the structuring of the wheat-materials, impacting the storage modulus, tan δ and printability. This work highlights the importance of tan δ for predicting the self-supporting ability of food materials. Keywords: 3D printing, starch, protein, thermomechanical process, microscopy, rheology 

Structuration de pâtes fortement hydratées par traitement thermomécanique 

Over the last 5 years, the growing interest of the researchers and the industry in 3D food printing has led to the development of this technology and to the formulation of a variety of printable edible materials. Extrusion printing technique which consist in the action of forcing the material through a die opening, have been used first for the printing of thermoplastics. Then, edible 3D object made of food materials with pasty texture were printed such as wheat dough (Liu, Liang et al., 2019;

Severini et al., 2018; Yang et al., 2018b), mashed potatoes (Liu et al., 2018a, 2018b, 2017b) or surimi paste (Wang et al., 2018). Studies of 3D printing of polylactic acid (PLA), which is a thermoplastic widely used in design and prototyping, highlighted the correlation between the viscosity of a material and its ability to be printed (Bakrani Balani et al., 2019; Khaliq et al., 2017). PLA is a solid-like material at room temperature and can only be extruded when heated above its melting transition temperature (about 200°C for semi-crystalline PLA) when its viscosity is lowered to about 2000 Pa.s (Bakrani Balani et al., 2019).

After extrusion, when deposited on the printing plate, this material solidifies quickly by going through the glass transition while cooling. To form an object in volume, the viscosity of the material must be high enough to form a layer that does not deform under its weight or the one of the layers deposited afterwards until the solidification transition is passed (Godoi et al., 2016). On the other hand, printing a high viscosity material requires a large amount of energy and can lead to increased pressure in the printer changing the printing flow rate.

Thus, shear-thinning fluids showing high viscosity at very low shear rates and a several orders of magnitude lower viscosity during extrusion could be compatible with 3D printing. Wheat flour dough was one of the first food material successfully 3D printed. The doughs of cereal products combine both shear-thinning behavior required, to some extent, during the extrusion step of the printing process (Jiang et al., 2019). These properties are related to the organization of the wheat flour components in the dough with the structuring effect of proteins at room temperature obtained by kneading and, in less extend, of the numerous starch granules dispersed in the dough.

The organization of the gluten proteins highly depends on the water content and the mixing process, which can lead to the formation of an elastic network of proteins in which starch granules are embedded (Auger et al., 2008). Wheat starch is a well-known food texturing agent (Rapaille and Vanhemelrijck, 1997) and a major component of wheat flour (between 70 to 80% of the dry mass). Wheat starch is composed of glucose polymers, amylose and amylopectin, organized in a semi-crystalline structure in the native starch granule.

Under heat treatment and in presence of water, the starch absorbs the water from the medium, loose its semi-crystalline structure and swells. This phenomenon affecting the structure of the granule is referred to as starch gelatinization. Depending on starch concentration and heating parameters, the swollen starch granules may be in contact with one another. They form a close-packed system of granules, which occupies a volume much higher than the one occupied by the continuous phase made of denatured wheat proteins which covers starch granules (Bagley and Christianson, 1982; Hermansson and Svegmark, 1996).