Carlos Eugenio Daudt

Potássio em uvas II: análise peciolar e sua correlação com o teor de potássio em uvas viníferas

Resumo O objetivo deste trabalho foi acompanhar a evolucao da absorcao de potassio pelas uvas durante o processo de maturacao e verificar sua influencia no pH, bem como tentar correlacionar ambas com os teores encontrados nos peciolos na epoca da floracao. Amostras das uvas foram coletadas durante o processo de maturacao de tres variedades: Pinot noir, Cabernet Sauvignon e Merlot. Durante os dois anos de estudo, ocorreram variacoes nos teores de potassio absorvidos pelos frutos durante a maturacao, sendo o aumento acompanhado pela elevacao do pH; a reducao no teor de potassio foi acompanhada pela estabilizacao dos valores de pH, fato tambem influenciado pela queda nos teores de acidez titulavel. Sugere-se, assim, que os altos valores de pH encontrados nos vinhos elaborados com uvas destes vinhedos, em anos anteriores, estao relacionados com a absorcao de potassio e a diminuicao da acidez total durante a maturacao da uva. A retirada de amostras peciolares na floracao e trinta dias apos mostrou-se um mecanismo eficiente na avaliacao do teor de potassio nos tecidos proximos aos graos. Dessa forma, a analise peciolar, alem de ser utilizada para monitorar os niveis de potassio na planta e avaliar a necessidade de adubacoes e tratos culturais, pode servir de diagnostico futuro para os teores de potassio nas uvas e nos vinhos. Palavras-chave: potassio; pH; uvas; fertilizacao.

Monitoring of wine aging process by electrospray ionization mass spectrometry

The characterization of wine samples by direct insertion electrospray ionization mass spectrometry (ESI-MS), without pre-treatment or chromatographic separation, in a process denominated fingerprinting, has been applied to several samples of wine produced with grapes of the Pinot noir, Merlot and Cabernet Sauvignon varieties from the state o Rio Grande do Sul, in Brazil. The ESI-MS fingerprints of the samples detected changes which occurred during the aging process in the three grape varieties. Principal Component Analysis (PCA) of the negative ion mode fingerprints was used to group the samples, pinpoint the main changes in their composition, and indicate marker ions for each group of samples.

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

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

Efeito da fertilização nitrogenada na cv. Gewürztraminer proveniente de duas regiões sobre a concentração de nitrogênio total no mosto e seu consumo por diferentes leveduras durante a fermentação alcoólica

The experiment was done with the grape variety Gewurztraminer from two regions of Rio Grande do Sul; different nitrogen treatments were done in the vineyard during the season of 1992-1993. The musts, of each treatment, were divided into four lots. Each lot was fermented with a different yeast. There was an increasing in the total nitrogen of the musts with the increase of nitrogen fertilization; these values ranged from a minimum of 376.1 mg/l to a maximum of 695.8 mg/l. In all small fermentation lots there was a decrease in the must total nitrogen; yeast used anywhere from 49.3% to 83.7% of nitrogent. Different yeasts showed difference in total nitrogen uptake.

Quantificação de 5-metiltetrahidrofolato no processamento e conservação de vinhos de uvas viníferas e híbridas

Folates are a class of vitamins that have been rediscovered in recent decades because of their association with various metabolic processes in the human organism. The main sources of folates described the scientific literature are vegetables, cereals and yeasts. The purpose of this study was to quantify 5-methyltetrahydrofolate (5-methyl-THF) in wines during wine production and aging. Red wines made from Cabernet Sauvignon, Merlot, and Pinot Noir wine grape varieties, and from Isabel (red) and Niagara (white) non-wine grape varieties were analyzed. The samples were analyzed at the beginning of fermentation, at the end of alcoholic and malolactic fermentation, and periodically at 4, 7, 12 and 24 months of age. High Performance Liquid Cromatography was used to separate, identify and quantify the folates. The results showed that the levels of 5-methyl-THF increased considerably during fermentation and continued to increase until the end of malolactic fermentation. The levels remained stable over a period of 3 to 6 months in the white wines and for 1 to 2 years in red wines, depending on the variety. The red wines proved to be a good source of 5-methyl-THF.

Um método rápido para análise de glicose em mostos e sua quantificação em algumas cultivares do Rio Grande do Sul

Glucose was analyzed in an eletronic equipment for glucose blood analysis (Checkmate Blood Glucose Monitoring System). There was no interference from fructose or sucrose. The amount of total reducing sugars was also analyyzed, by chemical methods, and fructose was calculated, approximatelly, by the difference between the two analysis. The method was quick, cheap, reliable and easy to handle in any industry which most of the time needs fast and practical results with little preocupations with accuracy. On the other hand, the evolution of these sugars was followed, from veraison to the harvest, in five red grape varieties. The amount of glucose was higher than fructose in all varieties with the exception of Tannat. The minimum and maximum values of total reducing sugars and glucose, at the harvest, varied from 162-212 g.1 and 99-111 g.1, respectivelly.

Presença de Cádmio em mostos e vinhos

Cadmium was analyzed in musts ana wines of two grapes varieties, Vitis vinifera Cabernet Sauvignon and Saint Emilion. Samples were taken during the alcohoolic fermentation as well as from the cap, seeds, lees and wines. Different quantities (5mg and 5mg/l) of cadmiun were added prior to start the fermentations. Cadmium was analysed by atomic absorption spectrometry using a graphite oven. The maximum values found, in mg/l, were respectively: wines control, 0.88: wines from musts with low Cd addition (5mg/l), 4.17 and wines from musts with high Cd addition (5mg/l), 280. The cadmium contem of the wines ranged from 32.5% and 60.1% of the cadmium originalty present in the musts. However, these amounts were considered low.

Evolução do teor de arginina e de uréia na fermentação alcoólica do mosto da cv Gewürztraminer com diferentes níveis de adubação nitrogenada

The experiment was done with the grape variety Gewurztraminer from Santana do Livramento, RS. The vineyard was treated with different nitrogen treatments during the 1992-1993 season. After harvest and crush, the must from each treatment was divided into four lots, and in each one was added a different yeast. During fermentation arginine decreased and urea increased. However, near the end of the fermentation process the available N urea started to be absorbed by the yeast.

ASPECTOS QUÍMICOS E MICROBIOLÓGICOS DE VINHOS DO RIO GRANDE DO SUL

Some chemical and microbiologycal aspects of one hundred (100) different wines bought in the local stores were studied in this work. Minimum, maximum, and average values for total and free SO2, ethanol, total and volatile acidity, total sugars and pH are given for fifty one (51) white, forty two (42) reds, seven (7) pink wines. Also, the amount of yeasts, other fungi, lactic and acetic bacteria are given for all the wines. Higher average values of total and free SO2 (124,2 and 18,9mg/l respectively) were found in the white wines, as expected. There was a direct relationship between the tow level of free SO2 and the contamination with yeasts and bacteria, also expected. However, red wines were more contaminated with yeasts than white wines, what was not expected.

Aminoácidos livres e uréia durante a fermentação do mosto de Cabernet Sauvignon com diferentes leveduras

The main aim of the fermentation of Cabernet Sauvignon Musts with different yeasts was the analysis of aminoacids and urea. The grape was chosen because its high proline and low arginine content.The grapes were harvested and crushed at the Almaden vineyard located in Santana do Livramento, RS, Brasil; the musts were transported to the Federal University of Santa Maria, Department of Food Science, where they were divided in two lots to which were added Saccharomyces cerevisiae Fermol Bouquet and Saccharomyces cerevisiae 2056. The analysis of the aminoacids was done using a Hitachi L-8500 aminoacid analyzer according to SANDERS and OUGH (21) and urea according ALMY and OUGH (1) modified by PEREIRA and DAUDT (19). Proline was found in the highest amount (847mg/l) followed by arginine (235mg/l) and alanine (87mg/l). The majority of the aminoacids fraction was used at the beginning of the fermentation with the exception of proline; this fact enfasized the low preference, by these yeasts, for this aminoacid. The aminoacids arginine, threonine, serine, aspartate and isoleucine can be considered better sources of nitrogen to the yeasts. The maximum excretion of urea in the must ocurred, with both yeasts, at the maximum arginine consumption, 2.7mg/l with the yeast 2056 at 19°Brix and 4.1mg/l with the yeast Fermol Bouquet at 15°Brix.