Influence de la culture intercalaire de ray grass sur la microflore des sols de vigne

Au cours de trois années, la culture intercalaire de ray grass a été comparée au travail traditionnel du sol. L'expérimentation a été conduite dans cinq terroirs viticoles de Touraine. Les paramètres p hysiques, chimiques et microbiologiques des sols sont mesurés au cours de trois saisons. Les caractéristiques viticoles sont déterminées une fois par an. L'analyse statistique des résultats montre que le terroir est le facteur principal, mais le climat et le traitement sont également responsables des modifications observées.La ctùture intercalaire de ray grass a stimulé très nettement la microflore du sol, en particulier les actinomycètes et des groupes fonctionnels des cycles de l'azote et du carbone. Elle a augmenté la valeur du pH du sol et modifié le rendement d'une façon variable selon les terroirs. L'utilisation de cette technique doit être adaptée à la nature du sol et aux conditions climatiques.Effect of intercalary ray grass culture on vineyard soil microfloraDuring three years, intercalary ray grass culture was compared with traditional soil maintenance. The experiment was carried out in five viticultural soils in Touraine. Physical, chemical and microbiological soil parameters were measured during three seasons. Viticultural features were determined once a year. Statistical analysis of results showed that soil is the main factor, but climate and treatment are also responsible for observed modifications. With intercalary ray grass culture, soil microflora, particularly Actinomycetes and functional groups of nitrogen and carbon cycle, is stimulated very clearly. pH value of soil is increased, yield is modified variably according to the soils. The use of that technique must be adapted to soil nature and climatic conditions

Essai d'utilisation de la microbiologie des sols pour tester l'efficacité des agents fertilisants

Dans cinq sols différents du vignoble de Touraine quatre agents fertilisants ont été comparés: fumier, compost urbain, engrais minéral, engrais organique. Pendant deux années d'observations les paramètres physico-chimiques et microbiologiques du sol sont mesurés au cours de trois saisons. Les caractéristiques viticoles sont déterminées une fois par an.En plus des différences liées aux saisons, aux années et aux sols, l'analyse statistique des résultats montre que les agents fertilisants employés sont responsables de modifications de la microflore surtout, des caractéristiques physico-chimiques du sol et dans une moindre mesure des caractéristiques viticoles.L'analogie entre l'effet du compost urbain et du fumier de ferme est remarquable. Tous deux accroissent le taux de matière organique, stimulent la microflore et limitent l'acidification des sols. L'engrais minéral et l'engrais organique abaissent la valeur du pH; peu de différences ont été notées entre ces deux agents fertilisants. Il apparaît que la microflore du sol réagit très rapidement aux modifications du sol par les pratiques culturales. Pour cette raison l'utilisation de la microbiologie du sol en viticulture permettrait ainsi de prévoir les phénomènes du sol.Using soil microbiology for testing fertilizers' efficacyIn five different soils of a Touraine vineyard, four fertilizers were compared: farm manure, waste compost, mineral fertilizer and organic fertilizer. During two years' observations physico-chemical and microbiological parameters were measured over three seasons. Viticultural features were determined once a year.In addition to differences caused by seasons, years and soils, statistical analysis of results shows that the fertilizers used are responsible for modifications, particularly of soil microflora, of soil physico-chemical features and, to a lower extent, of viticultural features.Analogy between the effect of waste compost and farm manure is remarkable. Both increase the amount of organic matter, stimulate microflora and restrict acidification. Mineral and organic fertilizers bring down pH value. Little differences are noted between those two fertilizers.It appears that microflora reacts very quickly to modification of the soil by cultural practices. For this reason, using soi! microbiology in viticulture would permit to predict phenomena in soil

The effect of yeast on the anthocyanin characteristics of fermented model solutions

The sensory quality of red wines is basically determined by the colour, which depends on the amount and on the evolution of anthocyanins and other phenolic compounds extracting from the berries into the wine during wine-making. The anthocyanin-monomers are responsible for the development of the red colour, and their acylated derivatives provide stability for the colour of the wines. The anthocyanin profile of wines is affected by several factors: the grape variety, the conditions during wine-making, and also the yeast culture used for the fermentation. In our experiments a self-compiled model solution was fermented by spontaneous fermentation, as well as by four commercial yeasts under laboratory conditions. After fermentation total polyphenolics, anthocyanins, anthocyanin monomer profile, colour intensity, hue, and the ratio of polymeric anthocyanins were studied. Our results show that the spontaneous yeast fermentation resulted in a higher anthocyanin concentration in the fermented model solution, but the commercial yeast strains provided a more advantageous colour characteristic compared to the spontaneous fermentation. After the spontaneous fermentation less sediment was left than in the commercial yeast fermented samples

Classification géographique de vins rouges par analyse de leur extrait sec en spectroscopie moyen infrarouge à transmission

276 vins de même cépage, le Gamay, ont été collectés durant 3 années (1998, 1999, 2000) et analysés par spectroscopie moyen infrarouge à transmission afin d'authentifier les régions d'origine, Gaillac, Beaujolais ou Touraine. Les analyses spectroscopiques en transmission sont réalisées sur des membranes en polyéthylène sur lesquelles 75 μL de vin mélangés avec le même volume d'acétone sont déposés et séchés sous vide au dessiccateur. Les données spectrales, comprises entre 800 cm-1 et 1800 cm-1, sont traitées par trois méthodes de classification: a) classement par la méthode du plus proche voisin (PPV); b) sélection pas à pas des nombres d'onde les plus significatifs associée à une analyse factorielle discriminante avec validation croisée (AFD); c) régression par les moindres carrés partiels (PLS). La première méthode (PPV) donne des résultats peu satisfaisants; 65% seulement des échantillons de validation sont correctement classés dans leur groupe d'origine. Par AFD et par PLS, les taux d'échantillon bien classés sont de 90% et de 85% respectivement

Effect of winemaking treatment and wine aging on phenolic content in Vranec wines

Phenolic compounds and colour stability of red wines produced from Vranec Vitis vinifera L. grape variety were investigated by means of different maceration times (3, 6 and 10 days), two doses of SO2 (30 and 70 mg/L SO2), two yeasts for fermentation (Vinalco and Levuline), temperature of storage and time of aging (3, 6 and 16 months). In general, maceration time influenced the phenolics extraction from the grapes into the wine. Highest concentrations of phenolic components were observed in the wines produced with 6 days of maceration, except for the flavan-3-ols which were present in highest amounts in the wines macerated for 10 days. Higher doses of SO2 increased the extraction of polyphenols, preventing the wines from oxidation, while the effect of yeast on phenolics extraction was not significant. Wine aging affected the phenolic content of wines produced with 3 days of maceration and caused intensive decrease of anthocyanins during the storage period. Wines aged at higher temperature showed lower anthocyanin levels and less intense coloration. Principal component analysis revealed that separation of the wines was performed according to the hue value in correlation with the maceration time and time of wine aging

Evolution during wine aging of colour and tannin differences induced by wine starters

The ability of threeSaccharomyces cerevisiae strains, with different colour adsorption aptitude, to induce and maintain colour differences in wines obtained from the Calabrian Gaglioppo and Magliocco black grape varieties was studied during one year of aging. The evolution of wine tannin content was also considered. Total polyphenols, colour parameters and total tannin values exhibited, both for Gaglioppo and Magliocco wines, significant (P < 0.05) or highly significant (P < 0.01) differences among strains. It is interesting to note that yeasts appear to exhibit a different adsorption aptitude for anthocyanins and tannins. The strain that gave wine with high values for the colour parameters was not the same as the one that produced wine with high values of tannins. The obtained results suggest that the choice of yeast strain in winemaking affects, in a significant way, the phenolic composition of wines with direct consequences on their colour and tannin content. Moreover, the interaction between grape cultivar and yeast is close and important, because grape variety, due to its phenolic composition, modulates yeast strain adsorption activity