Protein haze formation in white wines: effect of saccharomyces cerevisiae cell wall components prepared with different procedures

Cell wall material was extracted by five different methods from an oenological strain of Saccharomyces cerevisiae. Enzyme preparations containing beta-glucanase activity (Zymolyase, Glucanex, and Finizym 250L) allowed a better extraction yield compared to that of dithiothreitol (DTT) and EDTA. The yeast extracts were only soluble in part in wine. The wine-soluble fraction (WSF) of the five extracts, differing in both protein and sugar contents, when added in increasing amounts to white wine differently affected protein haze formation, as determined by the heat test, giving dose/response curves of different shapes. The curves obtained with the WSF derived from DDT and Zymolyase extracts showed a plateau value corresponding to 90% and 80% of wine haze reduction, respectively. In contrast, addition of the WSF derived from the other extracts resulted in increased turbidity with respect to the original wine. The mannoproteins (MP), isolated from each yeast extract by Concanavalin-A chromatography, gave dose/response curves showing shapes more similar among them than those obtained with the whole WSFs. The best wine stabilization was obtained with the MP of the DTT and Zymolyase extracts. The supernatants obtained after heating the MP of the different extracts were also tested. The stabilizing effect of the heat-stable MP (HSMP) was always larger than that of the corresponding total (un-heated) MP. The HSMP obtained starting from the DTT and Zymolyase extracts showed the best haze-protecting effect, which was, however, lower than that obtained with their corresponding WSF. This result suggests that wine protein stabilization by compounds of the yeast cell wall could be related, in addition to the action of the MP, also to the presence of other substances of different nature.     

Optical sensor for sulfur dioxide determination in wines

A method for the determination of free and total sulfur dioxide in wines, based on the use of an optical sensor that employs a dichlorobis(diphenylphosphino)methane dipalladium I complex [Pd(2)(dppm)(2)Cl(2)] immobilized in a PVC membrane plasticized with o-nitrophenyloctylether (o-NPOE) is described. A sensing membrane [4.2% Pd(2)(dppm)(2)Cl(2), 20.8% PVC, and 75% o-NPOE] was adapted to the tip of a bifurcated optical fiber bundle to perform reflectance measurements at 550 nm. The detection system consisted of two cells (40 mL), which hold the sample solution (plus reagents) and the optical sensor, respectively. For the determination of free SO(2), a wine sample was mixed with H(2)SO(4) solution in the sample cell, into which N(2) was bubbled, providing mixing of the solutions and conducting the SO(2) formed toward the detection cell. For determination of total SO(2), a KOH solution was mixed with the wine in the sample cell. Afterward, an H(2)SO(4) solution was added to the cell, and then N(2) was bubbled to conclude the measurement. Linear responses up to 50 and 150 mg L(-1) were obtained for free and total SO(2), with detection limits of 0.37 and 0.70 mg L(-1), respectively. The repeatability of the method was evaluated by carrying out 10 measurements using a single wine sample, providing relative standard deviation values of 2.2 and 2.5% for free and total SO(2), respectively. The sensing membrane prepared from 10 muL of the cocktail solution lasted for 80 measurements, whereas those prepared from 200 muL can be used for 250 measurements. The method was applied to free and total SO(2) determination in wines, and the results did not show significant difference from those obtained with the Ripper reference method at a confidence level of 95%.     

Identification of anthocyanin-flavanol pigments in red wines by NMR and mass spectrometry

Three newly formed Port wine pigments were isolated by Toyopearl HW-40(s) gel chromatography and semipreparative HPLC. Furthermore, the pigments were identified by mass spectrometry (LC/MS) and NMR techniques (1D and 2D). These anthocyanin-derived pigments showed UV-visible spectra different from those of the original grape anthocyanins. These pigments correspond to malvidin 3-glucoside linked through a vinyl bond to either (+)-catechin, (-)-epicatechin, or procyanidin dimer B3 [(+)-catechin-(+)-catechin]. NMR data of these pigments are reported for the first time.     

Characterization of wines by nuclear magnetic resonance: a work study on wines from the Basilicata region in Italy

We explored the possibility of differentiating Italian wines produced in different regions by means of nuclear magnetic resonance (NMR) techniques. Ten commercial red Aglianico wines were selected from different areas of the Basilicata region in the south of Italy. Some important components of these wines were identified by the assignments of their (1)H and (13)C resonances using one- and two-dimensional homonuclear and heteronuclear NMR experiments. These data were compared with those obtained from 10 Aglianico wines produced in Campania, another southern Italian region. Differences were found among the wines according to their geographical origin and vintage. A fine discrimination of Aglianico wines from Basilicata and Campania was obtained, suggesting that the selected NMR parameters may be a valuable tool for wine authenticity control.     

Determination of 4-ethylphenol and 4-ethylguaiacol in wines by LC-MS-MS and HPLC-DAD-fluorescence

Volatile phenols produced by Brettanomyces dekkera have been associate with off-flavors of wines. A versatile liquid chromatography-tandem mass spectrometry together with an HPLC-DAD-fluorescence methods were developed for the quantitation of two phenols, 4-ethylphenol (4EP) and 4-ethylguaiacol (4EG), in red and white wines. For LC-MS-MS analysis, fortified wines were directly injected after a dilution with methanol, and levels of phenols were measured by monitoring the multiple reaction (MRM) transitions of precursor ions mass charge (m/z) 121 --> 106 for 4EP and (m/z) 151 --> 136 for 4EG. Qualitative and quantitative confirmation data were acquired simultaneously by monitoring alternative MRM transitions following an external standard method. Calibration was linear over a working range of 10 and 5000 microg/L. Limit of determination (LOD) and limit of quantification (LOQ) were 10 and 50 microg/L for both 4EG and 4EP. HPLC analysis phenols were separated with a gradient system of acetonitrile-water and detected using a diode array detector (DAD) at 280 nm, and for the fluorescence analysis, excitation and emission wavelengths of 260 and 305 nm were used. Quantitative analysis of 4EP and 4EG was performed by the standard addition method to avoid matrix interferences. Calibration was linear over a concentration range from 10 to 5000 microg/L for HPLC-DAD, from 1 to 10,000 microg/L for 4EP, and from 10 to 10,000 for 4EG for fluorescence analysis. LOD and LOQ for the DAD analysis were 10 and 50 microg/L for both 4EG and 4EP. For fluorescence analysis, LOD and LOQ were 1 and 5 microg/L for 4EP and 10 and 50, respectively, for 4EG. The proposed methods can be easily used for the qualitative and quantitative determination of 4EP and 4EG in wines affected by microbial contamination with yeasts of the Brettanomyces genus.     

Evolution of residual levels of six pesticides during elaboration of red wines. Effect of wine-making procedures in their dissappearance

The effect of wine-making procedures on the concentrations of six pesticides (chlorpyrifos, penconazole, fenarimol, vinclozolin, metalaxyl, and mancozeb) in red wines has been studied. During maceration stage (4 days), the percentage remaining of chlorpyrifos, penconazole, and metalaxyl was approximately 90%, whereas that of fenarimol, vinclozolin, and mancozeb is somewhat smaller (74-67%). The residual levels found in pressed must were 相似文献   

Simple method for derivatization of monoglycerides and diglycerides

A method has been developed for derivatization of monoglycerides and diglycerides to their propyl esters by using propionic anhydride in the presence of pyridine. The derivatives are volatile and thus can be separated and identified by gas chromatography (GC). Completion of the reaction is monitored by thin-layer chromatography. Monoglyceride propyl esters were positively identified by gas chromatography and by gas chromatography/mass spectrometry. No side products were observed in the derivatization reaction which requires 35 min at 75 degrees C. GC analysis of the mono- and diglyceride propyl esters can be completed in approximately 30 min.     

Analytical and sensorial characterization of the aroma of wines produced with sour rotten grapes using GC-O and GC-MS: identification of key aroma compounds

In the present work, the aroma profiles of wines elaborated from sound and sour rot-infected grapes as raw material have been studied by sensory analysis, gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS), with the aim of determining the odor volatiles most likely associated with this disease. The effect of sour rot was tested in monovarietal wines produced with the Portuguese red grape variety Trincadeira and in blends of Cabernet Sauvignon and sour rotten Trincadeira grapes. Wines produced from damaged berries exhibited clear honey-like notes not evoked by healthy samples. Ethyl phenylacetate (EPhA) and phenylacetic acid (PAA), both exhibiting sweet honey-like aromas, emerged as key aroma compounds of sour rotten wines. Their levels were 1 order of magnitude above those found in controls and reached 304 and 1668 μg L(-1) of EPhA and PAA, respectively, well above the corresponding odor thresholds. Levels of γ-nonalactone also increased by a factor 3 in sour rot samples. Results also suggest that sour rot exerts a great effect on the secondary metabolism of yeast, decreasing the levels of volatiles related to fatty acids and amino acid synthesis. The highest levels of γ-decalactone of up to 405 μg L(-1) were also found in all of the samples, suggesting that this could be a relevant aroma compound in Trincadeira wine aroma.     

Red and white wines inhibit cholesterol oxidation induced by free radicals

The capabilities of two red (RW) and two white wines (WW) in inhibiting cholesterol oxidation were evaluated using a cholesterol emulsion (CE) system. Each RW or WW was mixed with CE at different (v/v) ratios. Cholesterol oxidation was accelerated by a free radical generator, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH), at 37 °C. The major oxidation product, 7-ketocholesterol, was monitored to determine cholesterol stability in the CE system. At a ratio of 1:250 (RW/CE), 7-ketocholesterol production was not detected during 72 h of oxidation. At a 1:1000 ratio, the inhibition rate of each RW was maintained at 100% at 24 h but decreased afterward. Both WWs had 100% inhibition rate within 48 h at a ratio of 1:10. Also, the capabilities of catechin and resveratrol solutions (1 mg/mL) in inhibiting cholesterol oxidation were studied. Each of the wine polyphenolics showed a 100% of 7-ketocholesterol inhibition rate in 24 h at a ratio of 1:500 (solution/CE). However, the inhibition rate of resveratrol was lower than that of catechin at 48 or 72 h. The results demonstrated that red wine possesses great anti-cholesterol-oxidation capability, which may contribute to health benefits in preventing cardiovascular diseases. Catechin may play a more important role than resveratrol in inhibiting cholesterol oxidation.     

Identification and quantification of impact odorants of aged red wines from Rioja. GC-olfactometry, quantitative GC-MS, and odor evaluation of HPLC fractions.

An XAD-4 extract from a 5-year-old wine from Rioja (Spain) was analyzed by aroma extract dilution analysis. Most of the odorants were quantified by GC-MS. A second extract was fractionated in an HPLC system with a C-18 semipreparative column. Fifty fractions were recovered, their alcoholic degree and pH were further adjusted to those of the wine, and those fractions that showed strong odor characteristics were further re-extracted and analyzed by GC-O and GC-MS. Reconstitution experiments were carried out to confirm the role of the odorants detected in the fractions. Fifty-eight odorants were found in the Rioja wine, 52 of which could be identified. Methyl benzoate was found to be a wine aroma constituent for the first time. The most important odorants are 4-ethylguaiacol, (E)-whiskey lactone, 4-ethylphenol, beta-damascenone, fusel alcohols, isovaleric and hexanoic acids, eugenol, fatty acid ethyl esters, and ethyl esters of isoacids, Furaneol, phenylacetic acid, and (E)-2-hexenal. Comparison among the three techniques shows good agreement and demonstrates that they are complementary.     

Postcolumn derivatization method for determination of reducing and phosphorylated sugars in chicken by high performance liquid chromatography

A postcolumn derivatization method is described for determination of reducing sugars and phosphorylated reducing sugars from chicken meat and other foods using high-performance liquid chromatography (HPLC). Reducing sugars are extracted with ethanol/water, separated on a Kromasil amine-bonded column by isocratic analysis using acetonitrile/water as the mobile phase, and, after postcolumn reaction with tetrazolium blue, are determined by the resulting absorbance at 550 nm. Phosphorylated sugars are first dephosphorylated using alkaline phosphatase and then determined by the same method.     

Assay of riboflavin in sample wines by capillary zone electrophoresis and laser-induced fluorescence detection

To routinely assay the concentration of riboflavin (RF) in wines, a rapid and sensitive method was developed and evaluated. The method is based on a simple sample preparation, capillary zone electrophoretic separation and laser-induced fluorescence detection (CZE-LIF). Sample preparation required only dilution and filtration. Under optimized conditions, the limit of detection of riboflavin was 0.5 micro g/L, using a hydrodynamic sample introduction of 10 s at 54 mbar. The method was fully validated: the recovery of RF in wines was >95%. The concentrations of RF within the three sample types of Italian wines investigated here ranged from 69 to 151 micro g/L with a mean value (+/-SD) of 112 +/- 25 micro g/L, from 74 to 193 micro g/L with a mean value of 115 +/- 45 micro g/L, and from 156 to 292 micro g/L with a mean value of 226 +/- 40 micro g/L, for white, rosé, and red wines, respectively. Such an accurate and highly sensitive CZE-LIF method represents a powerful improvement over previous methods in terms of sensitivity, simplicity, and efficiency. It is well suited to satisfy the demands for accurate and sensitive detection with minimal sample preparation and cleanup.     

Analysis of volatiles in Pinotage wines by stir bar sorptive extraction and chemometric profiling

A fast, simple, cost-effective, and reliable method based on stir bar sorptive extraction (SBSE) in the headspace mode was used for the analysis of 39 volatile components in Pinotage wines. The method was sensitive, with LODs ranging from 50.0 pg/L to 281 ng/L and LOQs between 180 pg/L and 938 ng/L. Precision was between 6 and 20%. The intermediate precision was within the acceptable range. Moreover, good calibration curves with R(2) > 0.99 for all compounds were achieved. The method was successfully applied for the analysis of 87 young Pinotage wines of vintages 2005 and 2006 collected from various South African regions. To characterize the results based on vintage and origin, the obtained concentrations of the compounds were subjected to chemometric analysis. Exploratory factor analysis (FA), principal component analysis (PCA), and analysis of variance (one-way ANOVA) were consecutively done. The chemometrics approach revealed a reasonable correlation among the volatile components of these wines, as well as with respect to their year of production.     

Confirmation of organothiophosphorus insecticide residues in fruit and vegetables by oxidative derivatization.

Oxidative derivatization of 10 organothiophosphorus insecticides at nanogram levels, with neutralized sodium hypochlorite (NaOCl) produced their respective P=O oxygen analogs, as shown by GC/MS and FT-IR analysis.In addition, phorate resulted in phorate oxon sulfoxide while methidathion gave a mixture of oxidation products. Four macro-scale oxidation products of methidathion were isolated by thin layer chromatography and 3 were identified, namely, methidaoxon, bis(2-methoxy-delta2-1,3,4-thiadiazolin-5-on-4-yl) sulfide, and the corresponding disulfide, by comparison of their infrared and mass spectra with those of authentic samples. The relative response to sulfide and disulfide products of the flame photometric detector in both the P- and S-modes is discussed. This derivatization is applied to the confirmation of chlorpyrifos, ethion, phorate, DMPA (Zytron), leptophos, and methidathion in celery, potatoes, lettuce, tomatoes, and apples at 0.25-0.5 ppm fortification levels.     

Detection and quantification of lysozyme in champagne wines

We describe here techniques to detect and quantify lysozyme in Pinot noir and Chardonnay Champagne wines. Using a dot-blot technique, lysozyme antibodies were able to recognize their antigens even when the concentration of lysozyme in wine was 75 mg/L. SDS-PAGE was the second technique used. After Coomassie Brilliant Blue (CBB) staining or antibody immunostaining was performed, the wine originating from the lysozyme-treated must gave only one band corresponding to the lysozyme. It is then possible to precisely determine the concentration of lysozyme in a must or a wine by densitometric measurement of this band. The control wine gave no band with the CBB staining, such as with the immunostaining. The quantification of lysozyme with HPLC is another useable technique because the lysozyme elution time is largely superior to that of all of the wine compounds. In wines, losses of lysozyme were higher when the enzyme was added at one time to the must (-34% for the Pinot noir and -37% for the Chardonnay) than when lysozyme is added in 2-fold both in the must and in the wine (around -26% for the two wines). The lowest diminution is observed when lysozyme was added to the wine only (-18%) in comparison to the addition to the must at 300 mg/L (-43%).     

Identification of amino acids in wines by one- and two-dimensional nuclear magnetic resonance spectroscopy

Amino acids are minor compounds in wines, but they have a profound influence on wine quality, and amino acids composition can be used to differentiate wines according to the vine variety, geographical origin, and year of production. The NMR signals of amino acids in NMR spectra are overlapped by the signals of other compounds present and especially by the signals of dominant compounds such as water, ethanol, and glycerol. In this work we used 1D (1)H and (13)C, 2D homonuclear COSY, TOCSY, and 2D heteronuclear HSQC and HMQC pulse sequences, also with an incorporated WET pulse sequence element that allows the simultaneous suppression of several frequencies. Complete (1)H and (13)C NMR assignments for 17 amino acids commonly present in wine and of gamma-aminobutyric acid at pH 3 have been achieved in wine sample of Sauvignon from the Coastal wine-growing region of Slovenia, vintage 1994.     

Determination of sulfur dioxide in grapes and wines

Reasons for using SO2 in wine and the theoretical aspects of this use are discussed. Data are summarized on the amounts of SO2 found in wines in California and around the world. Methods of analysis are discussed.     

棉花秸秆糖化碱预处理条件优化

新疆含有丰富的棉花秸秆资源,但棉秆需经预处理后才能被纤维素酶高效水解。该文以棉花秸秆资源的综合利用为目的,对其碱预处理及微波/碱预处理条件进行了试验,结果表明：2.0%NaOH,固液比1︰20,120℃,处理棉花秸秆75 min,棉秆中的木质素、半纤维素含量分别降低60.42%,35.05%;利用碱/微波（700 W）预处理棉花秸秆15 min,棉花秸秆中的木质素、半纤维素分别降低61.31%,44.78%,提高微波功率对于处理后的棉秆中木质素、高聚糖（纤维素+半纤维素）收率无明显影响,但功率越高、所需时间越短;不同预处理后的棉花秸秆酶水解试验表明,碱预处理棉花秸秆酶水解96 h,水解率为20.01%,碱/微波预处理棉花秸秆酶水解48 h,水解率为20.05%。     

One-step derivatization and preconcentration microextraction technique for determination of bisphenol A in beverage samples by gas chromatography-mass spectrometry

A simple technique based on ultrasound-assisted emulsification microextraction in situ derivatization (USAEME-ISD) is proposed for the one-step derivatization, extraction, and preconcentration of bisphenol A (BPA) in beverage samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. BPA was in situ derivatized with acetic anhydride and simultaneously extracted and preconcentrated by using USAEME. Variables affecting the extraction efficiency of BPA were evaluated. Under optimal experimental conditions, the detection limit (LOD) was 38 ng L(-1) with a relative standard deviation (RSD) value of 11.6%. The linear working range was 100-1250 ng L(-1), and the coefficient of estimation (r(2)) of the calibration curve was ≥0.9971. The robustness of the proposed methodology was probed by developing a recovery study at two concentrations (125 and 500 ng L(-1)) over different beverage samples. This study led to a satisfactory result achieving recoveries of ≥82%, which showed acceptable robustness for determination of nanograms per liter of BPA in samples of food safety interest.     

Fining treatments of white wines by means of polymeric adjuvants for their stabilization against browning

Browning and maderization represent important problems for white wine stability. Essentially, this is due to polyphenol oxidation in the wine. The problem has been remedied by adsorption of polyphenol compounds with polymeric adjuvants (chitosans, scleroprotein, and polylactic acid) not used traditionally in wine-making. In particular, some chitosans reduced the polyphenol content and stabilized two Italian white wines (Trebbiano and Albana) to the same extent as did potassium caseinate, an adjuvant normally used in enology. Moreover, chitosans could be reused after a simple regeneration process.