Contribution à l’identification de facteurs impliqués dans le phénomène de giclage de la bière en vue du développement d’une méthode de détection précoce du « risque giclage »

Abstract : Beer gushing is an explosive over-generation of foam following the opening of a bottle. It is highly dependent on barley growing and harvesting climatic conditions and has been observed more frequently over the past years. Current technics, such as the modified Carlsberg test, only provide informations on a predictive gushing potential of malt with a large uncertainty. A rapid screening test on raw material leading to the identification of actual factor(s) responsible for the gushing is consequently highly required by the brewing industry. But a lack of informations about the compounds involved in gushing limits the development of such a technic. The initial goal of this study was to identify the compounds involved in beer gushing. This approach has been applied to industrial malts presenting gushing potential or not and artificially contaminated barleys in order to set a procedure to isolate compounds which may trigger gushing. In a first time, malt extracts, which are complex mixtures, have been produced and fractionated according to the properties of compounds such as their size, their foaming capacity or hydrophobicity. A good reduction of complexity of sample has been obtained after membrane filtration. Nevertheless, compounds like carbohydrates, proteins and polyphenols could not have been separated. Besides, separation by hydrophobicity has provided good information about the diversity of proteins but the analysis of their gushing potential remains difficult. Afterwards, in order to investigate the production of compounds by fungus at the surface of barley simulating real field crop production conditions, an artificial contamination was achieved and surface extraction with ultrapure water has been performed. Extracted molecules have been screened for their gushing activity. Thus, a purification of molecules by reverse phase chromatography allowed to isolate a gushing fraction from the surface extract. This fraction, which concentrates the gushing properties, is composed by proteins with high hydrophobicity which may be involved in gushing. This fraction was analyzed more in depth with a 2DE, and led to the identification of proteins all produced by fungus family. Among them, a protein called Epl1 appears to be of interest and could be a good candidate thanks its properties closed to hydrophobins (size and hydrophobicity). In conclusion, this methodology is developed to acquire a better knowledge about compounds produced by fungi at the surface of barley as well as to some industrial malt
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Theses
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http://docnum.univ-lorraine.fr/ulprive/DDOC_T_2017_0195_BILLARD.pdf
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https://hal.univ-lorraine.fr/tel-01906105
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Submitted on : Friday, October 26, 2018 - 2:19:12 PM
Last modification on : Saturday, October 27, 2018 - 1:16:55 AM

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Julien Billard. Contribution à l’identification de facteurs impliqués dans le phénomène de giclage de la bière en vue du développement d’une méthode de détection précoce du « risque giclage ». Ingénierie des aliments. Université de Lorraine, 2017. Français. ⟨NNT : 2017LORR0195⟩. ⟨tel-01906105⟩

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