Attaques chimique et biologique des effluents agricoles et agroalimentaires sur les matériaux cimentaires

Les effluents d’élevage ou de l’industrie agroalimentaire, tels que les lisiers, les jus d’ensilage ou les lactosérums, sont des milieux très agressifs pour les ouvrages agricoles en béton. En effet, ces effluents contiennent des bactéries et des acides organiques, deux agents potentiellement agressifs pour la matrice cimentaire. Les objectifs de cet article sont de caractériser les attaques associées à chacun des vecteurs agressifs et de déduire les paramètres de composition des liants favorisant leur durabilité en milieu agricole et agroalimentaire. Des éprouvettes de pâte de ciment ont été immergées dans trois types de solutions : un mélange d’acides organiques, afin d’analyser l’attaque associée à la partie acide des effluents, un lisier et un lactosérum de façon à analyser, pour ces effluents aux pH sensiblement différents, l’effet spécifique des bactéries dans la dégradation. Les modifications chimiques et minéralogiques ont été explorées par des analyses par microsonde électronique et diffraction des rayons X, associées à des observations au microscope électronique à balayage. Les résultats montrent que l’attaque associée à la partie acide des effluents se traduit par une décalcification quasi-totale de la matrice cimentaire, la zone dégradée étant constituée d’un squelette silicoalumineux quasi-amorphe. L’influence de la présence des bactéries sur les modes de dégradation et sur les cinétiques d’altération dépend grandement du pH de l’effluent

Masking of Several Olfactory Notes by Infra-threshold Concentrations of 2,4,6-Trichloroanisole

Introduction Among wine defects, 2,4,6-trichloroanisole has a specific impact on wine perception. In addition to giving to the wine an unpleasant odor, 2,4,6-trichloroanisole has a masking effect on notes. In this study, the specificity and efficacy of the masking effect of 2,4,6-trichloroanisole was tested at infra- and supra-threshold concentrations. A simplified model of a binary mixture was also studied for in-depth analysis of this phenomenon. Methods Techniques used included sensory analysis (odor profiling), psychophysical tests (threshold measurement and triangle test), chemical analyses (GC-MS), and a mono/dichorhinic stimulation paradigm, to test the hypothesis of peripheral interaction. Results The results revealed that TCA had a masking effect on a range of aromatic notes, even at infra-threshold concentrations. However, they also showed counteraction of odorant specificity by 2,4,6-trichloroanisole. The origin of this masking effect was also discussed. The results suggested that this interaction can be assumed to take place at receptor level. Conclusion This study provided experimental confirmation of the widespread idea that constituents in non-perceptible concentrations influence the perceived quality of mixtures of odorous compounds. Implications Moreover, this type of olfactory model may improve our understanding of combinatorial olfactory encoding at the peripheral level

The complexity of wine: clarifying the role of microorganisms

The concept of wine complexity has gained considerable interest in recent years, both for wine consumers and wine scientists. As a consequence, some research programs concentrate on the factors that could improve the perceived complexity of a wine. Notably, the possible influence of microbiological factors is particularly investigated. However, wine complexity is a multicomponent concept not easily defined. In this review, we first describe the actual knowledge regarding wine complexity, its perception, and wine chemical composition. In particular, we emphasize that, contrary to expectations, the perception of wine complexity is not related to wine chemical complexity. Then, we review the impact of wine microorganisms on wine complexity, with a specific focus on publications including sensory analyses. While microorganisms definitively can impact wine complexity, the underlying mechanisms and molecules are far from being deciphered. Finally, we discuss some prospective research fields that will help improving our understanding of wine complexity, including perceptive interactions, microbial interactions, and other challenging phenomena