Chauffage de la vendange : les technologies disponibles et les méthodes de vinifications associées

National audienc

Las tecnologías de elaboración de vinos con bajo contenido alcohólico

Michel Moutounet y sus colaboradores nos ofrecen una detallada revisión de las tecnologías existentes actualmente para reducir el contenido alcohólico en vinos y hacer frente a los efectos de la sobremaduración de la uva como consecuencia del calentamiento global

Ethanol and aroma compounds transfer study for partial dealcoholization of wine using membrane contactor

Correspondance: [email protected] the present work viability of membrane contactors application to partial dealcoholize wines was checked using synthetic wine solutions. A hollow fiber polypropylene (PP) membrane contactor was employed. The process was performed at room temperature and using the most frequent component concentrations present in real wines. The influence of feed and stripping flow rates variation was analyzed. A model considering three resistances in series was developed to predict the ethanol and aroma compounds behavior inside the membrane contactor. Detailed study of the contribution of the individual resistances for ethanol showed that the major contribution to the transport resistance was due to membrane one. The membrane mass transfer coefficient can be calculated using Dusty-gas model expression obtaining a value of . Flavor losses are higher when ethanol content reduction in feed phase increases. Aroma compound losses can reach almost 100% for the most volatile compounds when residence time of the feed stream is larger. A partial dealcoholization of 2% (v/v) gives as a result acceptable aroma losses that do not damage the final perceived quality of the product. A validation on a real wine was performed with an associated sensorial analysi

Effect of flash release treatment on phenolic extraction and wine composition

International audienceThe flash release (FR) process, consisting of rapidly heating the grapes and then applying strong vacuum, has been proposed to increase the polyphenol content of red wines. Its impact on polyphenol extraction kinetics and on the polyphenol composition of red juice and wines was studied over two seasons on different grape varieties (Grenache, Mourvedre, Carignan). The FR process allows fast extraction of all phenolic compounds (hydroxycinnamic acids, flavonols, anthocyanins, catechins, proanthocyanidins) and can be used to produce polyphenol-enriched grape juices. However, the concentration of all polyphenols dramatically decreased throughout fermentation when pressing was achieved immediately after FR. The FR wines made with pomace maceration were also enriched in polyphenols compared to the corresponding control wines. Increasing the duration of high-temperature exposure in the FR treatment further increased extraction of phenolic compounds but also accelerated their conversion to derived species. The tannin-to-anthocyanin ratio was particulary low in the wine fermented in the liquid phase, higher after FR than in the control, and even higher after longer heating. FR resulted in an increased tannin-to-anthocyanin ratio and an increased conversion of anthocyanins to tannin-anthocyanin adducts showing the same color properties as anthocyanins. The tannin-to-anthocyanin ratio was particulary low in the wine fermented in the liquid phase that also contained larger amounts of orange sulfite bleaching-resistant pigment

Characterization of suspended solids in thermo-treated red musts

Aims : Thermo-treatment of grapes, followed by pressing and fermentation in liquid phase, is a growing practice in red winemaking to obtain light and fruity wines. Must clarification before fermentation, a key step to get the expected wine profile, is hardly controlled and strongly varies between different musts. To better understand this variability and its potential impact on quality, suspended solids in several red musts were characterized and the performances of different clarification techniques compared. Methods and results : Results show a large variability in turbidity and total wet suspended solids between different raw and clarified musts, and a lack of correlation between these values. Clarification is always higher for vacuum filtration than for disk-stack or decanter centrifugation, with strong differences between musts for a given process. Despite a large size distribution, most of suspended particles are micronic and submicronic. TEM observations and analyses indicate that they are mostly membrane and organelle fragments along with (macro)molecular aggregates formed during juice extraction. Their overall composition differs from that found in white musts. Conclusion : Particle heterogeneity and size distribution account for the difficulties encountered in red must clarification. Results also raise the question of the relationship between must turbidity and content in compounds likely to affect wine quality. Significance and impact of the study: This study constitutes a first characterization of suspended solids in thermo-treated red musts. It provides elements to (i) reason their clarification and (ii) identify the technological and qualitative impact of must suspended solids

Partial Removal of ethanol during fermentation to obtain reduced-alcohol wines

Correspondance auteur: Camarasa C. E-mail: [email protected] audienceThe demand for wines with lower alcohol content has increased over recent years. There are various techniques for lowering alcohol content, including ethanol extraction from the wine and reduction of sugar content of the musts. The feasibility and potential importance of ethanol extraction techniques during wine fermentation were determined. In 100 L pilot-scale fermentations, 2% ethanol was removed halfway through fermentation, either by distillation under vacuum or by stripping with CO2. Despite being stressful for the yeasts, none of these treatments had a negative effect on fermentation kinetics. On the contrary, the fermentation rate increased, probably due to the extraction of inhibitory compounds and, consequently, the fermentation was easier to complete. Removing 2% ethanol during the course of fermentation slightly affected the final concentration of compounds derived from yeast redox metabolism (glycerol, acetate) and aromatic molecules. Both treatments lowered the volatile compounds content (by 25% and 45% for fusel alcohol and esters, respectively), but these losses were partly compensated for by synthesis in the second part of fermentation. The final concentrations were thus close to or even higher for glycerol and isobutanol (tip to 19% and 32% depending on the treatment, respectively) than those of the control fermentation. In addition, sensory analysis detected no significant difference between wines produced with or without dealcoholization treatment, except for a slight negative effect with stripping. Removing 2% ethanol by stripping or by distillation during the fermentation are promising alternatives for reducing the alcohol content of wine without altering the sensory quality of the produc

Stress hydrique prolongé des vignes : comment adapter les pratiques œnologiques en conséquence ?

Ce numéro d'Innovations Agronomiques comprend les articles correspondant aux présentations du colloque « Viticulture et stress hydrique » qui s'est tenu à Montpellier le 17 juin 2014.National audienceIn the general context of climate change and environmental requirements, similarly to precision viticulture, a new type of enology, called "precision enology", was set up for the treatment of harvests of vines experiencing prolonged water stress. The quality of the corresponding wines is not conventionally optimal, and it is then all the work of the winemaker to correct the physico-chemical and sensory balances of these wines. This intervention of the winemaker comes from the harvest throughout the succession of operations of the winemaking in connection with the control of oxidation phenomena. On the final wine, the winemaker should precisely control extractions, stability and organoleptic balance up to the packaging. The potential interventions are linked in particular with the alcohol content of wine and the global acidity and pH balances. For this, membrane technologies by their potential control by on-line sensors and their specificity provide answers to these scientific and technological challenges. Such recent innovations now permitted by regulation are already available as true service deliveries.Dans un contexte de changement climatique, d’exigences environnementales, à l’instar de la viticulture de précision, une œnologie dite « de précision » se met en place pour des vendanges en situation de stress hydrique prolongé. La qualité de ces vins n’est pas classiquement optimale et c’est tout le travail de l’œnologue que de retrouver les équilibres physico-chimiques et sensoriels perdus. Cette œnologie d’intervention se décline sur la vendange tout au long de la succession des opérations unitaires de la vinification en lien avec la maîtrise des phénomènes d’oxydation. Sur vin, il s’agit de maîtriser les extractions en cours de vinification, la stabilité et leur équilibre organoleptique jusqu’au conditionnement. Les interventions de l’œnologue se font en lien en particulier avec la teneur des vins en alcool et leur équilibre au niveau acidité et pH. Pour cela, les technologies membranaires de par leur pilotage par des capteurs en ligne et leur spécificité permettent de répondre à ces défis scientifiques et technologiques. Il s’agit d’innovations récentes, permises maintenant par la réglementation et déjà disponibles sur le terrain en traitement de prestation de service

Le décanteur centrifuge Alfa-Laval : apport d'un nouvel outil pour le prétraitement de la vendange thermotraitée avant fermentation

National audienc

Vinifications en rouge : macérations post fermentaires, macérations carboniques, flash détente sous vide

National audienc

Analyse des risques psychosociaux et de la qualité de vie au travail. Diagnostic et préconisations (unité expérimentale Pech Rouge)

il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : ACTIVITY_REPORTAnalyse des risques psychosociaux et de la qualité de vie au travail. Diagnostic et préconisations (unité expérimentale Pech Rouge