Thèse soutenue

Maltage à faible hydratation : dégradation des structures pariétales, diffusion et modification des protéines aleuroniques et caractérisation des barrières hydrophobes cuticulaires
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Auteur / Autrice : Jean-Luc Runavot
Direction : Didier MarionBénédicte Bakan
Type : Thèse de doctorat
Discipline(s) : Sciences biologiques et médicales, Biochimie
Date : Soutenance en 2011
Etablissement(s) : Nantes
Ecole(s) doctorale(s) : École doctorale Végétal-Environnement-Nutrition-Agro-Alimentaire-Mer (Angers)
Partenaire(s) de recherche : autre partenaire : Université de Nantes. Faculté des sciences et des techniques

Mots clés

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Résumé

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During kilning, reduction of energy costs without impacting significantly the malt quality, represents a major challenge of the malting industry. This energy reduction requires a reduction of barley grain water content at the end of steeping and during germination. In the present work, we focused on key malting quality parameters involved in diastatic power and foam promoting capacities of malt. When analysed in a low hydrated malt and a high hydrated malt, the LTP1 (a foam promoting protein) modifications and its diffusion from the aleurone layer to the starchy endosperm were similar. The hydration level of the grain affects however β-glucanase diffusion and activity, and consequently the β-glucan degradation. These effects are linked to a delay in the synthesis and the diffusion of these enzymes. An increase of the time of germination allows to sharply reduce these effects. According to grain hydrophobic barriers localized at the pericarp surface and at the interface of aleurone and pericarp (testa), water diffusion inside the grain follows a specific pathway. Only weak, although significant, differences in cuticular thickness and composition were observed between cultivars with different malt qualities according to their hydration levels. On the contrary, we observed a great variability in the cuticular composition of the various tissues of the grain e. G. Scutellum, chalaza or husk.