Recherche et Estimation du Saccharose Ajouté aux Moûts et aux Vins à l'Aide de la Chromatographie sur Papier

La chromatographie de partage sur papier nous a permis de mettre au point une technique spécifique très sensible de recherche du saccharose dans les moùts et les vins. En raison de la présence de saccharase, l'efficacité de la recherche du sucrage basée sur cette méthode est conditionnée par la rapidité du prélèvement et de l'exécution du dosage

Dosage Microbiologique des Acides Aminés des Moûts de Raisin et des Vins

Nous avons déterminé au moyen des méthodes microbiologiques classiques dix-sept acides aminés se trouvant à l'état libre dans une série de moûts et de vins. Ces méthodes s'appliquent parfaitement à ces milieux sans autre traitement préalable qu'une neutralisation et une dilution convenable. L'arginine, la praline, la thréonine, l'acide glutamique sont les quatre acides aminés les plus abondants. Ils représentent plus de 85 0/o de l'azote aminé des moûts; dans les vins cependant, ils ne constituent plus qu'une fraction de 60 %. La fermentation alcoolique fait apparaître en effet de petites quantités d'acides aminés qui n'existaient pas à l'état libre dans les moûts; la composition azotée des vins est moins abondante mais plus variée que celle des moûts. Ces dosages montrent encore que les taux des acides aminés assimilables par les levures selon la réaction d'EHRLICH sont absents dans le moût de raisin, ou seulement présents à doses extrèmement faibles. Entre autres conséquences qui découlent de ces observations et contrairement aux notions admises jusqu'à maintenant, l'alcool isobutylique et l'alcool isoamylique des vins ne tirent leur origine que pour une part très minime de la valine et des leucines des moûts.Enfin s'il existe une certaine concordance entre les chiffres d'azote aminé obtenus par dosage microbiologique et par formoltitration dans le cas des vins rouges, les écarts obtenus pour les moûts et surtout les vins blancs suggèrent que les techniques microbiologiques dosent encore certains petits polypeptides pouvant être dégradés par les bactéries

Adaptation and Validation of QUick, Easy, New, CHEap, and Reproducible (QUENCHER) Antioxidant Capacity Assays in Model Products Obtained from Residual Wine Pomace

Evaluation of the total antioxidant capacity of solid matrices without extraction steps is a very interesting alternative for food researchers and also for food industries. These methodologies have been denominated QUENCHER from QUick, Easy, New, CHEap, and Reproducible assays. To demonstrate and highlight the validity of QUENCHER (Q) methods, values of Q-method validation were showed for the first time, and they were tested with products of well-known different chemical properties. Furthermore, new QUENCHER assays to measure scavenging capacity against superoxide, hydroxyl, and lipid peroxyl radicals were developed. Calibration models showed good linearity (R2 > 0.995), proportionality and precision (CV < 6.5%), and acceptable detection limits (<20.4 nmol Trolox equiv). The presence of ethanol in the reaction medium gave antioxidant capacity values significantly different from those obtained with water. The dilution of samples with powdered cellulose was discouraged because possible interferences with some of the matrices analyzed may take place.The autonomous government of Castilla y León (Project BU268A11-2

Efeito do ácido tartárico nos valores de potássio, acidez titulável e pH durante a vinificação de uvas Cabernet Sauvignon

Vinhos tintos com altos valores de pH são resultantes de uvas com valores excessivos de potássio. O excesso de potássio é, geralmente, resultado, do manejo inadequado no vinhedo. Com o intuito de encontrar uma solução tecnológica para o problema de pH nos mostos antes e durante da aplicação de medidas no vinhedo, foram realizadas vinificações em escala piloto com uvas Cabernet Sauvignon adicionando-se ácido tartárico no momento do esmagamento. Assim, três tratamentos, em duplicata, foram feitos com a adição de zero (testemunha), 1 e 2gL-1 de ácido tartárico. Foram utilizados os procedimentos normais de sulfitagem, uso de enzimas pectinolíticas e leveduras selecionadas. A descuba foi realizada após 10 dias e a fermentação malolática foi espontânea. Foram analisados potássio (por fotometria de chama), acidez titulável (por titulometria) e pH (por peagâmetro) no mosto durante a fermentação e no vinho resultante. Potássio foi também analisado nas películas e nas borras submetidas, no entanto, a digestão nitroperclórica antes da análise. Os valores encontrados para potássio (gL-1), acidez titulável (g%) e pH durante a microvinificação foram, respectivamente, na amostra testemunha: 1,98, 0,61, 3,68; tratamento 1: 1,72, 0,70 e 3,63; tratamento 2: 1,41, 0,73 e 3,50. A análise de potássio, nas películas e nas borras nos diferentes tratamentos, apresentou os seguintes valores, respectivamente, para a amostra testemunha em g kg-1 (Matéria Seca): 24,91 e 69.30; tratamento 1: 21,85 e 75.11; tratamento 2: 16,20 e 85.38. A ação do ácido tartárico torna-se mais evidente nas borras, em que quanto maior foi a adição de ácido no mosto maior foi a quantidade de potássio encontrada nestas, reduzindo, desse modo, a quantidade de potássio no vinho. Salienta-se que a adição de ácido tartárico é um paliativo momentâneo e a verdadeira correção deve ser feita no vinhedo, por meio de um manejo adequado.Wines with high pH values are usually made from grapes with high potassium values and can bring serious problems to the wine. This high potassium comes, usually, from mistakes with the vines management. While the right management has being tried, in the vineyard, and aiming to find a fast solution for the problem inside the winery a pilot scale fermentation was made with Cabernet Sauvignon. The must was submitted to three different treatments with tartaric acid: zero, 1gL-1 and 2gL-1,all in duplicate. The pattern of fermentation was the normal SO2, pectinolitic enzymes and yeasts addition to the musts; skins and seeds were removed from the must after 10 days of fermentation and malolactic fermentation occurred spontaneously. Potassium (by flame spectrometry), total acidity (by titulometry) and pH (by pH meter) were analyzed in the musts during fermentation and in the wines; skins and lees were digested previously the analysis. Values found, in the wines, for potassium (gL-1), total acidity (g%) and pH were respectively: samples from zero tartaric acid 1,98, 0.61, 3,68; from 1gL-1:1,72, 0.70 e 3,63; from 2gL-1:1,41, 0,73 e 3,50. Values found in the skins and lees with the same treatments were, respectively: 24,91 and 69.30, 21,85 and 75.11, 16,20 and 85.38g kg-1 of the Dry Matter. The effect of tartaric acid addition was noted mainly in the lees (69.3, 75.11 and 85.38), in which the potassium found showed a close relationship with the acid added in the must. It should be noted, though, that this addition is just for the moment because the real correction should be made in the vineyard, as it is now

A new method for the detection of early contamination of red wine by Brettanomyces bruxellensis using Pseudomonas putida 4-ethylphenol methylene hydroxylase (4-EPMH)

Brettanomyces/Dekkera bruxellensis is a cause of major concern for the winemaking industry worldwide. If a slight presence of this spoilage yeast in red wine adds a Brett character, a strong contamination has irreversible and detrimental effects on the organoleptic qualities due to the production of volatile phenols such as 4-ethylphenol. Time is a key factor in the treatment of B. bruxellensis contaminations. Nowadays, the diagnostic and quantification resources available are time consuming and too expensive, making them either inadequate or inaccessible to most of the winemakers. This study was focused on a new, easy to use, inexpensive method that could allow winemakers to directly detect B. bruxellensis contamination in red wine at an early stage, hence, reducing wine spoilage. In this work, the ability of Pseudomonas putida 4-ethylphenol methylene hydroxylase was tested in order to catabolize the 4-ethylphenol and to elaborate an enzymatic assay with the purpose of detecting early contaminations by B. bruxellensis in red wine. We have developed a colorimetric enzymatic assay, based on the redox state of the 4-ethylphenol methylene hydroxylase co-factor, cytochrome C, that can detect and quantify low concentrations of 4-ethylphenol. The range of concentrations detected is well below the level detectable by the human nose. Combined to an enrichment step, this method allows the detection of B. bruxellensis at an initial concentration of less than 10 cells per ml