Incidence des conditions de conservation des vins blancs sur leur teneur en composés soufrés volatils

Dans ce travail, nous avons étudié lincidence de quelques paramètres de conservation des vins issus des cépages blancs grecs, Batiki et Rhoditis, sur leur teneur en composés soufrés volatils. Il est demontré que le stade du sulfitage des vins nouveaux joue un rôle important sur la formation de ces substances, ainsi que laération qui entraîne leur diminution. De plus, la conservation des vins en barrique ou en cuve, avec les lies ou non, influence dune manière différente la teneur des vins en substances soufrées volatiles. Influence of white wine conservation conditions on the levels of volatile sulphur compoundsIn the present study, the effects of various parameters of white wine conservation on the level of volatile sulphur compounds were examined. Wines from the Greek white cvs Batiki and Rhoditis were fermented. H2S was analysed colorimetrically, the more volatile sulphur compounds by headspace-gas chromatography (GC) coupled with flame photometry detection (FPD) and the less volatile sulphur compounds by liquid extraction-GC/MS. The best time to sulphurize a young wine is 5-6 d after the end of alcoholic fermentation in order to avoid the accumulation of sulphur substances, especially in wines intended to age on lees, Aeration of wine causes a notable decrease of the more volatile sulphur compounds, whereas the diminution is less important for the less volatile sulphur compounds. Furthermore, the amount of volatile sulphur compounds is affected by the conservation of wines in barriques or in stainless tanks, the duration of contact of wine with its lees, as well as the duration of conservation

Study of anthocyanins' variations during the ripening of five vine red varieties cultivated in Greece

The anthoeyanins' variations in grape skins during the ripening of five vine varieties, cultivated in various vinegrowing areas of Greece were studied. The anthocyanins were separated and determined by HPLC. It was found that: - Dp-3-gluc and Cy-3-gluc contents decrease constantly for all varieties during ripening, - Pt-3-g1uc content is the same, early in the ripening but close to maturity it decreases significantly, - Pn-3-g1uc and Mv-3-g1uc contents are the highest all over ripening and for all the varieties studied, - Mv-3-g1uc-ac and Mv-3-g1uc-coum are the most important from the acylated derivates. It is therefore concluded that during grape maturation, anthocyanins' contents change in the same way, not depending on the vine variety

Artificial Immune Classifier Based on ELLipsoidal Regions (AICELL) †

Pattern classification is a central problem in machine learning, with a wide array of applications, and rule-based classifiers are one of the most prominent approaches. Among these classifiers, Incremental Rule Learning algorithms combine the advantages of classic Pittsburg and Michigan approaches, while, on the other hand, classifiers using fuzzy membership functions often result in systems with fewer rules and better generalization ability. To discover an optimal set of rules, learning classifier systems have always relied on bio-inspired models, mainly genetic algorithms. In this paper we propose a classification algorithm based on an efficient bio-inspired approach, Artificial Immune Networks. The proposed algorithm encodes the patterns as antigens, and evolves a set of antibodies, representing fuzzy classification rules of ellipsoidal surface, to cover the problem space. The innate immune mechanisms of affinity maturation and diversity preservation are modified and adapted to the classification context, resulting in a classifier that combines the advantages of both incremental rule learning and fuzzy classifier systems. The algorithm is compared to a number of state-of-the-art rule-based classifiers, as well as Support Vector Machines (SVM), producing very satisfying results, particularly in problems with large number of attributes and classes

Determination of benzothiazole in grapes and wines

Benzothiazole was measured in grapes from Muscat Lefko vines from the Isle of Samos and in Muscat d'Alexandrie vines from the Isle of Lemnos. Differences were noted in regard to altitude, soil composition and exposure, and in the corresponding wines. This compound was also determined in grapes of ten other white grapevines cultivated in Greece, and in their corresponding wines. The results show the presence of benzothiazole in all of the grapes examined, and that it might have been formed during the maturation of the grape. The levels of benzothiazole varied from 0.8 to 6.1 mug/l; this was always below the threshold of perception

Molecular identification of wine yeasts at species or strain level: A case study with strains from two vine-growing areas of Greece

The composition of wine yeast populations, present during spontaneous fermentation of musts from two wine-producing areas of Greece (Amyndeon and Santorini) and followed for two consecutive years, were studied using a range of molecular techniques. Internal Transcribed Spacer (ITS) ribotyping was convincingly applied for yeast species identification, proving its usefulness as a reliable tool for the rapid characterization of species composition in yeast population studies. Restriction Fragment Length Polymorphism (RFLP) of mitochondrial DNA (mtDNA) was shown to be a convenient criterion for the detection of intraspecies genetic diversity of both Saccharomyces and non-Saccharomyces isolate populations. Similarly, polymorphism of amplified δ interspersed element sequences provided an additional criterion for S. cerevisiae strain differentiation. Comparative analysis of S. cerevisiae genetic diversity, using mtDNA restriction patterns and δ-amplification profiles, showed a similar discriminative power of the two techniques. However, by combining these approaches it was possible to distinguish/characterize strains of the same species and draw useful conclusions about yeast diversity during alcoholic fermentation. The most significant findings in population dynamics of yeasts in the spontaneous fermentations were (i) almost complete absence of non-S.cerevisiae species from fermentations of must originating from the island Santorini, (ii) a well recorded strain polymorphism in populations of non-Saccharomyces species originating from Amyndeon and (iii) an unexpected polymorphism concerning S. cerevisiae populations, much greater than ever reported before in similar studies with wine yeasts of other geographical regions

Molecular identification of wine yeasts at species or strain level: A case study with strains from two vine-growing areas of Greece

The composition of wine yeast populations, present during spontaneous fermentation of musts from two wine-producing areas of Greece (Amyndeon and Santorini) and followed for two consecutive years, were studied using a range of molecular techniques. Internal Transcribed Spacer (ITS) ribotyping was convincingly applied for yeast species identification, proving its usefulness as a reliable tool for the rapid characterization of species composition in yeast population studies. Restriction Fragment Length Polymorphism (RFLP) of mitochondrial DNA (mtDNA) was shown to be a convenient criterion for the detection of intraspecies genetic diversity of both Saccharomyces and non-Saccharomyces isolate populations. Similarly, polymorphism of amplified δ interspersed element sequences provided an additional criterion for S. cerevisiae strain differentiation. Comparative analysis of S. cerevisiae genetic diversity, using mtDNA restriction patterns and δ-amplification profiles, showed a similar discriminative power of the two techniques. However, by combining these approaches it was possible to distinguish/characterize strains of the same species and draw useful conclusions about yeast diversity during alcoholic fermentation. The most significant findings in population dynamics of yeasts in the spontaneous fermentations were (i) almost complete absence of non-S.cerevisiae species from fermentations of must originating from the island Santorini, (ii) a well recorded strain polymorphism in populations of non-Saccharomyces species originating from Amyndeon and (iii) an unexpected polymorphism concerning S. cerevisiae populations, much greater than ever reported before in similar studies with wine yeasts of other geographical regions

Influence of cluster thinning on the amino acids concentration of musts and wines of the variety Vilana. Effect on wine volatile compounds

In this work, the influence of cluster thinning on the amino acids concentration of musts and wines was studied. Three vineyards were selected from Peza district of Crete where the white vine variety Vilana is cultivated. One part of each vineyard, containing 100 vines was divided in two sections. The first was used as reference while in the second section, cluster thinning to 50%, just before veraison, was applied. The experimentation was repeated for two continuous years. In 1996, the reference sections yielded 35.5 – 46.7 t/h while the other sections, where cluster thinning took place, yielded 16.5 – 23.0 t/h. The next year, the yields were 43.2 – 48.4 t/h and 12.6 – 14.0 t/h respectively. In all musts and wines, 18 amino acids were determined with the use of HPLC and proline was determined colorimetrically. The volatile components of the wines were also measured because, as it is known, the amino acids contribute to the formation of some higher alcohols, ethyl esters and acetates. From this work the following conclusions were made: The musts and the wines from Vilana variety are poor in amino acids and their levels vary from one year to another. This variation is related to the climatic conditions of the period of maturation but the profile of these acids seems invariable. The musts of Vilana variety deriving from vineyards with cluster thinning, which lead to low yield, contain higher levels of amino acids. This is important, given that a must rich in amino acids, positively influences not only the fermentation process evolution but also the enrichment of the wines in volatile components. Particularly for the Vilana variety, which is poor in amino acids and without any typical aroma, the high yields have a negative effect on their wine quality