mL Of Wine Research Articles

Quantitative determination of trace and ultratrace flavour active compounds in red wines through gas chromatographic–ion trap mass spectrometric analysis of microextracts

A GC–MS method for analysing the most important flavour active odorants of wine has been developed. The method combines a two-step preconcentration stage (demixing+microextraction) and a GC–ion trap MS determination. In the method, 50 ml of wine are previously adjusted to 13% (v/v) alcohol, and the alcoholic fraction is demixed by salting out. That fraction is partially rediluted, extracted with 0.1 ml of 1,1,2-trichlorotrifluoroethane (freon 113) and analysed by GC–MS to obtain quantitative information on 25 analytes whose concentrations range from 0.1 to more than 1000 μg/l. Those analytes are esters, alcohols, terpenols, aromatic ketones, lactones, ethers and volatile phenols. The overall method R.S.D. ranges from 3 to 7%, and the linear behaviour is very good except for the most concentrated analytes. Standard addition experiments and analyses of spiked samples have demonstrated that both the MS quantification and the overall method are free of matrix effects, and that only two internal standards are needed. The limits of detection range from 20 to 1000 ng/l, and all the analytes can be detected at the concentration in which they become flavour active.

Development of a Method for Analyzing the Volatile Thiols Involved in the Characteristic Aroma of Wines Made fromVitis viniferaL. Cv. Sauvignon Blanc

Volatile thiols were purified from a dichloromethane extract of Sauvignon blanc wine by the reversible combination of the thiols with p-hydroxymercuribenzoate, fixation of the resulting complex in an anion exchange column, and finally release of the thiols with cysteine. By analyzing the purified thiol extract from 500 mL of wine, using gas chromatography coupled with mass spectrometry, it was possible to measure the concentrations of five volatile compounds at once: 4-mercapto-4-methylpentan-2-one, 3-mercaptohexyl acetate, 3-mercaptohexan-1-ol, 4-mercapto-4-methylpentan-2-ol, and 3-mercapto-3-methylbutan-1-ol. Analysis of 10 typical Sauvignon Blanc wines (Bordeaux, Sancerre) showed that the first three compounds listed above are expected to be involved in varietal aroma, as they may be present at concentrations greatly in excess of their respective perception thresholds. Keywords: Volatile thiol; aroma; Sauvignon blanc wine; Vitis vinifera; p-hydroxymercuribenzoate

Moderate and Large Doses of Ethanol Differentially Affect Hepatic Protein Metabolism in Humans ,

The intake of ∼70 g of alcohol impairs liver protein metabolism in healthy humans. To establish the threshold at which alcohol impairs hepatic protein metabolism in humans we compared the effects of 500 mL of water (control study), 300 (28.4 g ethanol) or 750 mL (71 g ethanol) of table wine on hepatic protein metabolism in three groups of healthy nonalcoholic volunteers. Hepatic protein metabolism was estimated (L-[1-14C]leucine infusion) by measuring the fractional secretory rates of albumin and fibrinogen during the overnight postabsorptive state (basal) and the subsequent administration of water or two different amounts of wine (300 or 750 mL) given with a liquid glucose-lipid-amino acid meal. During the meal, water did not affect fibrinogen fractional secretory rate and increased albumin fractional secretory rate by ∼50% (P < 0.01). The 300 mL of wine increased albumin secretory rate by only ∼20% (P < 0.01 vs. basal, P < 0.04 vs. water) and did not affect fibrinogen secretory rate. The 750 mL of wine profoundly impaired hepatic protein metabolism, decreasing the fractional secretory rates of albumin (P < 0.01 vs. water and 300 mL wine) and fibrinogen (P < 0.04 vs. water and 300 mL of wine) below the postabsorptive values. These results demonstrate that a moderate dose of alcohol (28 g, ∼2 drinks) slightly affects postprandial hepatic protein metabolism by blunting the meal-induced increase in albumin synthesis, whereas it does not interfere with fibrinogen synthesis as do higher doses.

Nicotinamide Counteracts Alcohol-Induced Impairment of Hepatic Protein Metabolism in Humans ,

We have recently shown that a large amount of wine (750 mL, ∼70 g of alcohol) markedly impairs postprandial hepatic protein metabolism in healthy subjects. This is probably due to the shift in the intracellular redox state (increased NADH/NAD+) induced by ethanol oxidation. If this hypothesis is true, the administration of nicotinamide (NAD+precursor) should provide NAD+in excess and thus correct the NADH/NAD+abnormalities and prevent the ethanol hepatotoxicity. Whole-body protein metabolism and the fractional secretory rates of hepatic (albumin, fibrinogen) and extra-hepatic (immunoglobulin G, IgG) plasma proteins were measured in the basal postabsorptive and in the absorptive states in 15 healthy subjects, that had been assigned to three groups matched for age and body mass index. During the absorptive state (intragastric meal), the three groups received water (control), 750 mL of wine, or 750 mL of wine + 1.25 g of nicotinamide, respectively. The redox state was estimated by determining the plasma lactate/pyruvate ratio. Compared with the basal state, wine alone increased the lactate/pyruvate ratio twofold and depressed the fractional secretory rates of albumin and fibrinogen (P< 0.01 vs. control and nicotinamide); nicotinamide reduced the effects of wine on the lactate/pyruvate ratio (P< 0.02 vs. wine alone) and prevented the reduction of albumin and fibrinogen secretory rates (P> 0.05 vs. control). These results indicate that nicotinamide counteracts the acute hepatotoxic effects of ethanol by ameliorating the redox state.

A soldier who had seizures after drinking quarter of a litre of wine

During a party to celebrate his initiation into an artillery regiment, in September, 1994, a healthy 19-year-old white man drank 250 mL of wine which had flowed through the barrel of a 155 mm gun after several shots had been fired, as was the regimental custom. 15 min later he began to have seizures which lasted for 25 min until they were stopped by intravenous diazepam. He was transferred to a teaching hospital in Limoges. On physical examination (BF), he was unconscious and did not react to any stimuli.

Determination of lead and arsenic in wines by electrothermal atomic absorption spectrometry

Methods for the determination of As and Pb in wines by electrothermal atomic absorption spectrometry (ETAAS) are proposed. For As, 8 ml of wine were diluted with 1 ml of nitric acid in a PTFE bomb, followed by heating to 150 °C for 90 min. The transparent solution obtained was diluted to 10 ml with de-ionized water. The integrated absorbances of the solutions were measured by ETAAS using 5 µg of Pd, as a chemical modifier. For Pb, the integrated absorbances were measured after diluting the wine sample, 1 + 4, with 0.2% nitric acid, using a mixture of 10 µg of Pd and 15 µg of Mg as modifier. The detection limits (k= 3) were 6.6 and 15.5 ng ml–1 for As and Pb, respectively, 20–30 times below the maximum limits proposed by the control agencies. Three wine samples were analysed and the concentrations found were below the maximum permissible concentrations. Recoveries were approximately 100%, for analytical solutions containing 10% v/v and 0.2% v/v of nitric acid, for As and Pb, respectively. No interference was observed.

Quantitative determination of sotolon in wines by high-performance liquid chromatography

Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) is a key flavour compound in the french flor-sherry “Vin jaune”. This compound was determined quantitatively by extraction of 25 ml of wine on a XAD-4 resin, elution with diethyl ether, separation by HPLC on a Lichrospher 100 Diol column, elution with dichloromethane/hexane (60/40) and UV detection at 232 nm. The amount of sotolon in “Vin jaune” (120 to 268 μg/l) was related to the development of the yeast film over a period of 6 years. Only 6 to 51 μg/l were found in the “Vin de paille” which is made with overmaturated grapes of the same Savagnin vine-plant but without development of yeasts, and 80 to 140 μg/l in “Tokai” which are partly grown under a yeast film.

Les acides gras libres du vin; observations sur leur origine

&lt;p style="text-align: justify;"&gt;L'addition d'écorces de levure ou de lies fraîches dans un milieu alcoolique entraîne une augmentation de la teneur en acides gras libres suivie d'une diminution progressive; les lies fraîches ne cèdent pratiquement pas d'acide palmitoléique, inhibiteur de l'activité malolactique.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;La teneur en acides gras libres augmente au cours de la macération des raisins rouges, mais elle est peu affectée par la macération préfermentaire des raisins blancs.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;Par ailleurs, les teneurs des vins en acides gras libres varient en fonction du cépage.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;+++&lt;/p&gt;&lt;p style="text-align: justify;"&gt;This work deals with the free latty acids (C12 to C18:3) content of different mediums; these substances seem to have an activity on the alcoholic and the malotactic fermentations.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;ln a first step we have studied the influence of the addition to the medium of yeast ghosts and fresh yeast cells (lees).&lt;/p&gt;&lt;p style="text-align: justify;"&gt;We have also determined free fatty acids in red wines (Merlot, Cabernet Sauvignon and Malbec) in function of the time of maceration (0 to 10 days) and in white wines (Semillon and Sauvignon blanc) in function of skin contact time (0 to 6 hours) and SO&lt;sub&gt;2&lt;/sub&gt; which have been added, or not, to the medium belore skin contact.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The free fatty acids were extracted from 20 ml of wine by three times 10 ml of dichloromethane ; the organic phase was concentrated under vacuum to 1 ml. The extract was analysed by gas chromatography with a capillary CP WAX 57 column from Chrompack (10 m x 0,22 mm); the chromotograph was equiped with a spitless system injector.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The addition of yeast ghosts and fresh lees into an alcoholic medium causes a temporary increase of the free fatty acids followed by a constant decrease. However, the fresh lees do not give palmitoleic acid which is an inhibitor of the malolactic activity.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The time of maceration plays a positive part on the free fatty acids content of the wine; this is more important for the red wines than for the white ones.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The free fatty acids content of the wines changes according to the grape variety.&lt;/p&gt;

Improved Gas Chromatographic Determination of Acetic Acid in Wines

An automated gas-liquid chromatographic method for the analysis of acetic acid in wines is described, which minimizes the often encountered difficulties of peak "tailing," broadening, and "ghosting". The method uses a 69 x 2 mm phosphoric acid-treated glass column, packed with 60/80 mesh Carbopack C, modified with 0.3% Carbowax 20M, and 0.1% H₃PO₄, which is extremely stable to aqueous injections. The accumulation of residues is eliminated by making a dilution of the sample, and using a glass insert in a low dead-volume injector port. Propionic acid is used as an internal standard, and helium carrier gas is saturated with formic acid to improve the chromatography. The method is rapid, accurate, and precise; giving a standard error of ± 0.0012 g acetic acid per 100 mL of wine, at the 0.005 to 0.054 g per 100-mL concentration level.

Oxidation of Wines. I. Young White Wines Periodically Exposed to Air

Chardonnay and Sauvignon blanc dry white table wines and a dry sherry from French Colombard plus Thompson Seedless were bottled in screw capped bottles holding 750 ml of wine with 25.0 ml of headspace and stored at 23.5°C (75°F). At weekly intervals the headspace air was replaced with the result that the wine was exposed to about 7 ml of oxygen per liter each week. Analyses of samples covering 10-12 weeks and oxygen exposure of 0 to 80 ml per liter were made. As oxygen exposure increased, fruitiness sensory rating and general quality decreased (for sherry it increased) and oxidation flavor rating increased. Pinking and browning spectral changes are discussed. Total phenol decreased 10-14 mg gallic acid equivalents per liter in 10 weeks exposure to oxygen and this decrease involved primarily the nonflavonoid components — not the flavonoids. Vicinal dihydroxyphenols accounted for only 27-54% of the total phenols oxidized in 10 weeks. Although decrease in total oxygen capacity as measured by uptake under alkaline conditions was only of the order of 4-6 ml over a 10-week exposure to oxygen, total exposure to 60 ml of O₂/l or so appears to be required to make the transition from table wine to sherry. Exposure to zero oxidation appears best for young white table wine quality although some indication of quality regeneration presumably with increased complexity at about 24 ml O₂/l exposure was found with the Sauvignon blanc samples.

A Modified Procedure for Alcohol Determination by Dichromate Oxidation

The chemical oxidation method for alcohol determination in wine after microdistillation of the samples is used routinely in many winery laboratories. However, analysts often experience a number of difficulties with the procedure, including use of the distilling apparatus and indicator endpoint when dichromate is titrated with ferrous ammonium sulfate. The procedure was modified to avoid some of the problems. Five ml of wine were distilled in a Cash volatile acid still, operated to ensure complete condensation and recovery of alcohol distillate in a 50-ml volume. Two ml of distillate were oxidized at 60°C with 10 ml of dichromate solution (34 g potassium dichromate plus 325 ml sulfuric acid per liter). Alcohol concentration was determined spectrophotometrically at 600 nm, according to Caputi et al. [Am. J. Enol. Vitic. 19:160-5 (1968)]. The method as modified provided acceptable speed, precision, and accuracy for routine analysis of wine alcohol.

Nonvolatile Acids in `Concord' Grape Wine

The nonvolatile acids of `Concord9 grape wine produced in Michigan in 1968 were determined qualitatively and quantitatively by column chromatography and paper chromatography, with the following results in mg per 100 ml of wine: Glutamic acid 1.1, aspartic acid 2.9, shikimic acid 5.1, lactic acid 72.0, galacturonic acid 64.0, succinic acid 28.4, citramalic acid 18.5, malic acid 48.9, tartaric acid 232.0 citric acid 49.5, and phosphoric acid 14.0. The titratable acidity was 5.7 meq/100 ml, the volatile acidity 1 meq/100 ml and the total (free acids and salts) acidity was 8.1 meq/100 ml.

Chemical and Sensory Effects of Heating Wines under different Gases

Heat treatment of a submerged-cultured flor sherry, with or without oxygen, decreased the flor character. Some apparent gain occurred in other aspects of sherry character, but indications are that the desired complexity can be produced more easily by other methods, such as blending, than by heating under the conditions tested. Table and dessert wines heated in the presence of oxygen-filled headspace (40 cc per about 750 ml of wine) changed in ways that were predominantly undesirable. Nitrogen hydrogen or carbon dioxide for dispacing the dissolved and headspace oxygen seemed equivalent in effect. In contrast to oxygen, these gases appeared in these tests behave as if inert and to have effect upon flavor changes during heating of the wine because oxygen had been displaced. Warming dessert wines at 128°F for up to 20 days in the presence of these inert gases caused definite chemical and sensory quality changes, most of them favorable. These changes appeared small, however, compared to the favorable effects produced in two table wines, particularly the white wine. Further studies have shown that not every wine responds equally favorably, though many are capable of improvement. In selected table wines, heating in the complete absence of oxygen for 15-30 days at about 128°F (53.4°C) produces definite improvement in bottle bouquet and increased complexity. An, negative factor can be a loss in grape aroma, if any is present. The nature of the bottle bouquet produced is discussed, along with its similarity to bouquet in bottled white table wines aged 3 to 4 years at wine-cellar temperatures. The conditions of the reaction of bottle bouquet formation appear to preclude enzymatic participation in the reaction because the temperature coefficient appears normal yet the products become noticeable only after a relativey long time at temperatures causing relatively rapid protein denaturation. This new treatment appears worthy of further trial. It appears to be capable of producing improved table wines with agedtype flavor from selected, pretested standard wines otherwise lacking notably high quality or desirable aroma. Blending such aged-type wine with fruity aromatic young wines might enable production of better white and light red table wines than if the fruity wine were itself subjected to long bottle aging.

Determination of Protein Stability in Wine

The amount of haze formed by the addition of 1 ml of 55 per cent tricholoroacetic acid to 10 ml of wine, followed by 2 minutes heating in boiling water, and a reaction period of 15 minutes at room temperature was found to correlate with protein stability as measured by the "heat-cold" test. The presence of unstable substances other than protein aparently does not affect the test.