Isolation and molecular identification of wine yeasts from a Brazilian vineyard

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Glucose and Fructose Fermentation by Wine Yeasts in Media Containing Structurally Complex Nitrogen Sources

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of caffeic acid in red wine by voltammetric method

The electrochemical oxidation of 3,4-dihydroxycinnamic acid, caffeic acid, leads to a stable electroactive poly(caffeic acid) thin film containing quinone moiety on a preactivated glassy polymeric carbon electrode. The properties of the deposited films as well as the stability study under different experimental conditions were investigated. Taking advantage of the electrochemical behavior, an analytical method based on differential pulse voltammetry for determination of caffeic acid in red wine was proposed.

Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l(-1) HNO3 and in 1 + 1 v/v diluted wine using mixtures of Pd(NO3)(2) + Mg(NO3)(2) and NH4H2PO4 + Mg(NO3)(2) as chemical modifiers. With 5 mug Pd + 3 mug Mg as the modifiers and a two-step pyrolysis (10 s at 400 degreesC and 10 s at 600 degreesC), the formation of carbonaceous residues inside the atomizer was avoided. For 20 mul of sample (wine + 0.056 mol l(-1) HNO3, 1 + 1, v/v) dispensed into the graphite tube, analytical curves in the 0.10-1.0 mug l(-1) Cd and 5.0-50 mug l(-1) Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 mug l(-1) for Cd, 0.8 mug l(-1) for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 mug l(-1) and for Pb at 500 mug l(-1). The relative standard deviations (n = 12) were typically < 8% for Cd and < 6% for Pb. The recoveries of Cd and Pb added to wine samples varied from 88 to 107% and 93 to 103%, respectively. The accuracy of the direct determination of Cd and Ph was checked for 10 table wines by comparing the results with those obtained for digested wine using single-element ET-AAS, which were in agreement at the 95% confidence level. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Altered patterns of maltose and glucose fermentation by brewing and wine yeasts influenced by the complexity of nitrogen source

Maltose and glucose fermentations by industrial brewing and wine yeasts strains were strongly affected by the structural complexity of the nitrogen source. In this study, four Saccharomyces cerevisiae strains, two brewing and two wine yeasts, were grown in a medium containing maltose or glucose supplemented with a nitrogen source varying from a single ammonium salt (ammonium sulfate) to free amino acids (casamino acids) and peptides (peptone). Diauxie was observed at low sugar concentration for brewing and wine strains, independent of nitrogen supplementation, and the type of sugar. At high sugar concentrations altered patterns of sugar fermentation were observed, and biomass accumulation and ethanol production depended on the nature of the nitrogen source and were different for brewing and wine strains. In maltose, high biomass production was observed under peptone and casamino acids for the brewing and wine strains, however efficient maltose utilization and high ethanol production was only observed in the presence of casamino acids for one brewing and one wine strain studied. Conversely, peptone and casamino acids induced higher biomass and ethanol production for the two other brewing and wine strains studied. With glucose, in general, peptone induced higher fermentation performance for all strains, and one brewing and wine strain produced the same amount of ethanol with peptone and casamino acids supplementation. Ammonium salts always induced poor yeast performance. The results described in this paper suggest that the complex nitrogen composition of the cultivation medium may create conditions resembling those responsible for inducing sluggish/stuck fermentation, and indicate that the kind and concentration of sugar, the complexity of nitrogen source and the yeast genetic background influence optimal industrial yeast fermentation performance.

OPTIMIZATION OF EXTRUSION COOKING PROCESS FOR CHICKPEA (CICER-ARIETINUM, L) DEFATTED FLOUR BY RESPONSE-SURFACE METHODOLOGY

Response surface methodology was employed to optimize the production of a snack food from chickpea. The independent variables, process temperature (123-137-degrees-C) and feed moisture (13-27% d.s.b.) were selected at five levels (rotatable five level composite design: - square-root 2, -1, 0, 1, + square-root 2) in the extrusion of defatted chickpea flour. Response variables were expansion ratio, shear strength of the extrudate and sensory preference assessed by an untrained panel. Expansion ratio increased steadily with decrease in feed moisture similar to cereal extrusion. Regions of maxima were observed for sensory preference and shear strength, and these two product attributes were linearly related. The most acceptable chickpea snack was rated higher than a commercial corn snack.

Pesticides in the distilled spirits of wine and its byproducts

The fate of eight fungicides (benalaxyl, fenarimol, iprodione, metalaxyl, myclobutanil, procymidone, triadimefon, and vinclozolin) and five insecticides (dimethoate, fenthion, methidathion, parathion methyl, and quinalphos) in wine and its byproducts (cake and lees) during the production of distilled spirits was studied. Among the pesticides studied, only fenthion, quinalphos, and vinclozolin residues were present in the distilled spirits. During wine distillation, respectively 13% and 5% of the initial residues of fenthion and vinclozolin were transferred to the distilled spirit. Low percentages (2% for fenthion and 0.1% for vinclozolin) of these active ingredients (AI) also passed from the lees to the final-distilled spirit, when samples were fortified at 10.1 and 26.1 ppm for fenthion and vinclozolin, respectively. Quinalphos passed only from the lees to the final-distilled spirit in percentages lower than 1% when samples were fortified at the highest concentration (4.6 ppm).

THE CASSAVA (MANIHOT-ESCULENTA, C) CV PIONEIRA .3. COOKING CHARACTERISTICS

The edible parts of cassava cultivar Pioneira roots after 12 and 24 months of cultivation were analysed for human consum. The yield was 63% when the roots were harvested at the right time (12 months), and lower (58%) for older roots, with 24 months. Total cyanide contents were 62,0 - 61,8 and 58,0 - 63,4 ppm, respectively. Cooking time was 13,5 min and 19,5 min, respectively, although the cooked mass quality was similar good. The edible part of the roots was processed in french fries or tholes, submited to two treatment: blanching for three minutes and boiling for ten minutes. Treated and in natura tholes were fried in vegetable oil at 190-degrees-C. The effect of freezing (-20-degrees-C for 60 days) on the cooking quality was also evaluated. The frozen storage reduced the total cyanid content in all treatment. The rate of cyanid decrease were 45%, 84% and 88% with frying, blanching and frying, and boiling and frying, respectively. Blanching followed by frying assured a safe cyanid level for human consum as well as a good acceptance in sensorial analysis. The influence of the age of the roots in cooking quality was a decrease in softness. Frozen storage softened the 24 month old roots and worsened the flavor of 12 month old root. For table purposes cassava roots should be processed in french fries and blanching, what would allow frozen storage of edible part.

Flow injection AAS determination of Cd, Cu, and Pb at trace levels in wine using solid phase extraction

A comparative study is reported between C-18 bonded silica gel and powdered polyethylene (PE) as sorbent for Cd, Cu, and Pb determination using ammonium diethyldithiophosphate (ADTP) as the complexing agent in a flow injection system. The complexes were formed in 0.14 mol L-1 HNO3 and processed in a simple flow system comprising a peristaltic pump, a manual injector-commutator, and a sorbent-packed minicolumn. Ethanol was selected as the eluent and analytes in the eluate were determined by flame atomic absorption spectrometry. The optimum concentration of the complexing agent was 0.1% (m/v) ADTP for Cu and Pb determination using either C-18 or PE, and 0.25% (m/v) ADTP for Cd determination using PE. The sample loading flow rates were 5.0, 3.6, and 3.0 mL min(-1) for Cu, Pb, and Cd, respectively. The best elution flow rate was 6.5 mL min(-1). For a 60-sec preconcentration time, the sampling rate was 40 h(-1) and the enrichment factors of 33, 36, and 11 times (C-18) or 18, 22, and 23 times (PE) were obtained for Cu, Pb, and Cd, respectively. The limits of detection (LOD) were 1.6 mug L-1 Cu, 11 mug L-1 Pb, and 2.0 mug L-1 Cd using C-18 or 2.9 mug L-1 Cu, 19 mug L-1 Pb, and 1.0 mug L-1 Cd using PE, respectively. The relative standard deviations (n = 12) were typically <2%, <2%, and <6% for Cd, Cu, and Pb, respectively. The recoveries of Cd, Cu, and Pb added to wine samples varied from 96-99%, 97-102%, and 90-99%, respectively, using C-18 or PE. Accuracy was checked for Cd, Cu, and Pb determination in six wine samples digested by block digestor and open-vessel microwave-assisted digestion systems. The results revealed that C-18 was more efficient for Cu and Pb determination, while PE was the best sorbent for Cd.

Persistence and Metabolism of Folpet in Grapes and Wine

The fate of folpet from the treatment on vine to the production of wine was studied. Sunlight degraded folpet to unknown products. Phthalimide was a minor metabolite formed on grapes from folpet. Folpet degraded in must, giving 80% phthalimide; the results obtained with model solutions showed that in must folpet can also give small amounts of phthalic acid. During wine-making folpet degraded completely, and at the end of fermentation phthalimide was only present in wine. This compound was stable in wine after several months. The presence of folpet in grapes inhibited the alcoholic fermentation of Saccharomyces cerevisiae and Kloeckera apiculata completely. Phthalimide, on the contrary, had no negative effect on the fermentative action of the two yeasts. GC and HPLC methods were developed to determine folpet and its metabolites.

Fate of Some New Fungicides (Cyprodinil, Fludioxonil, Pyrimethanil, and Tebuconazole) from Vine to Wine

The fate of four new fungicides (cyprodinil, fludioxonil, pyrimethanil, and tebuconazole) from the treatment on vine to the production of wine was studied. The influence of clarifying agents (bentonite, charcoal, potassium caseinate, gelatin, and polyvinylpolypyrrolidone) on residue concentrations in wine was also studied. The fungicide residues on grapes showed different decay rates after treatment, with first-order kinetics and half-lives ranging from 8 to 57 days. Grape processing into wine caused considerable residue reduction with cyprodinil (ca. 80%), fludioxonil (ca. 70%), and tebuconazole (ca. 50%) and no reduction with pyrimethanil. The two wine-making techniques employed (with and without maceration) had the same influence on the residue concentrations in wine, except for fludioxonil which showed maximum residue reduction with vinification with maceration. Among the clarifying agents tested, only charcoal showed effective action on the elimination of residue content in wine, proving complete elimination, or almost, of fungicide residues.

Gas Chromatographic Determination of Cyprodinil, Fludioxonil, Pyrimethanil, and Tebuconazole in Grapes, Must, and Wine

A rapid and simple gas chromatographic method for determinating cyprodinil, fludioxonil, pyrimethanil, and tebuconazole in grapes, must, and wine is described. An on-line microextraction method was used with a one-step extraction-partition procedure. Nitrogen-phosphorus and mass spectrometric detectors were used, because of their low sensitivity and high selectivity. Because of high selectivity of detector, no cleanup was necessary and the extract was concentrated 5 times. Recoveries from fortified grapes, must, and wine ranged from 93 to 110%. Limits of determination were 0.05 mg/kg for cyprodinil and pyrimethanil and 0.10 mg/kg for fludioxonil and tebuconazole.