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10 pages, 1139 KiB

Open AccessArticle

Advances in the Dereplication of Aroma Precursors from Grape Juice by Pretreatment with Lead Acetate and Combined HILIC- and RP-HPLC Methods

by Michele D’Ambrosio

Foods 2019, 8(1), 28; https://doi.org/10.3390/foods8010028 - 15 Jan 2019

Cited by 4 | Viewed by 4018

Abstract

Glycosidic aroma precursors (GAPs) contribute to the varietal flavor of wine. Researchers have applied various sample preparation and analytical methods in attempts to achieve their separation and identification. However, mass spectrometric methods still fail to unequivocally define their structures. We have previously reported [...] Read more.

Glycosidic aroma precursors (GAPs) contribute to the varietal flavor of wine. Researchers have applied various sample preparation and analytical methods in attempts to achieve their separation and identification. However, mass spectrometric methods still fail to unequivocally define their structures. We have previously reported the separation of GAPs in their natural form and elucidated their structures by nuclear magnetic resonance (NMR) spectroscopy. In this study, we confirm the effectiveness of our established procedure and present methodological improvements. Grape juice was treated with lead (II) acetate and repeatedly chromatographed to give seven pure GAPs. Their chemical structures were characterized by MSⁿ fragmentations and 1D- and 2D-NMR spectra. Ten GAPs were analyzed by both hydrophilic interaction liquid chromatography (HILIC) and reversed phase high performance liquid chromatography (RP-HPLC) to compare the two chromatograms. A selection of known phenols was treated with lead (II) acetate in order to check its binding properties. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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18 pages, 1670 KiB

Open AccessArticle

Basic In-Mouth Attribute Evaluation: A Comparison of Two Panels

by Mihaela Mihnea, José Luis Aleixandre-Tudó, Martin Kidd and Wessel du Toit

Foods 2019, 8(1), 3; https://doi.org/10.3390/foods8010003 - 21 Dec 2018

Cited by 8 | Viewed by 3543

Abstract

Astringency is often difficult to evaluate accurately in wine because of its complexity. This accuracy can improve through training sessions, but it can be time-consuming and expensive. A way to reduce these costs can be the use of wine experts, who are known [...] Read more.

Astringency is often difficult to evaluate accurately in wine because of its complexity. This accuracy can improve through training sessions, but it can be time-consuming and expensive. A way to reduce these costs can be the use of wine experts, who are known to be reliable evaluators. Therefore, the aim of this work was to compare the sensory results and the panel performance obtained using trained panelists versus wine experts (winemakers). Judges evaluated twelve red wines for in-mouth basic perception (sweet, sour, bitter, astringent, and burning sensation) following the same tasting protocol and with the samples being presented in two different tasting modalities. Panels’ performance and relationship between the chemical composition and the sensory perception were investigated. Both panels showed similar consistency and repeatability, and they were able to accurately measure the astringency of the wines. However, the significant correlations between sensory scores and chemical composition varied with the panel and the tasting modality. From our results, we could see that winemakers tended to discriminate better between the samples when the differences were very small. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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17 pages, 1108 KiB

Open AccessArticle

Impact of Commercial Oenotannin and Mannoprotein Products on the Chemical and Sensory Properties of Shiraz Wines Made from Sequentially Harvested Fruit

by Sijing Li, Keren Bindon, Susan Bastian and Kerry Wilkinson

Foods 2018, 7(12), 204; https://doi.org/10.3390/foods7120204 - 12 Dec 2018

Cited by 16 | Viewed by 4847

Abstract

The tannin and polysaccharide profiles and therefore sensory properties of wine are influenced by fruit maturity at harvest, and practices employed during winemaking. This study investigated the extent to which commercial winemaking supplements (skin and seed tannins, and mannoprotein (MP)) can enhance the [...] Read more.

The tannin and polysaccharide profiles and therefore sensory properties of wine are influenced by fruit maturity at harvest, and practices employed during winemaking. This study investigated the extent to which commercial winemaking supplements (skin and seed tannins, and mannoprotein (MP)) can enhance the mouthfeel properties of red wine, in particular, wine made from grapes harvested before commercial ripeness (early-harvest). Supplements were added to wines made from Shiraz grapes harvested at 20.8 and 24.5 °Brix. The chemical composition and mouthfeel properties of wines were then determined by high performance liquid chromatography and descriptive analysis (DA), respectively. Wines made from riper grapes had higher levels of tannin than wines made from early-harvest grapes, but similar polysaccharide levels were observed. The addition of seed oenotannin yielded higher tannin levels than addition of skin oenotannin, particularly for wines made from early-harvest grapes. The DA panel perceived sensory differences between H1 and H2 wines, but could not perceive any effect of supplementation on wine mouthfeel properties, with the exception of a minor increase in sweetness, attributed to mannoprotein addition to H1 wines, even when MP was added to wines at 2.5 times the level recommended for use in Australia. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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14 pages, 1302 KiB

Open AccessArticle

Testing the Sensitivity of Potential Panelists for Wine Taint Compounds Using a Simplified Sensory Strategy

by Marianne McKay, Florian F. Bauer, Valeria Panzeri and Astrid Buica

Foods 2018, 7(11), 176; https://doi.org/10.3390/foods7110176 - 24 Oct 2018

Cited by 12 | Viewed by 5932

Abstract

The odor detection threshold (ODT) of a compound is the lowest concentration at which individuals can reliably perceive a difference between a sample and its corresponding control, with 50% performance above chance. Wine is a complex matrix, and ODTs used in studies on [...] Read more.

The odor detection threshold (ODT) of a compound is the lowest concentration at which individuals can reliably perceive a difference between a sample and its corresponding control, with 50% performance above chance. Wine is a complex matrix, and ODTs used in studies on wine can be based on inappropriate matrices and informal sensory methodologies. Formal studies confirming ODTs in wine are relatively scarce in the literature, and are complex and expensive to carry out. In this study, the sensitivity of panelists to previously published ODTs for five compounds: Guaiacol, o-cresol and 4-ethyl phenol, 3-isobutyl-2-methoxypyrazine (IBMP), and 2,4,6-trichloroanisole (TCA) associated with off-flavor/taint issues in wine, was investigated. The study was carried out in partially de-aromatized young Shiraz wine (unwooded) using a simplified version of the formal sensory approach. A triangle test in triplicate was carried out with 34 panelists, at the ODT for each compound, in one day. The study explored whether previous training affected panelists’ sensitivity for threshold differences. Results showed that samples spiked with volatile phenols were significantly different (p = 0.01) to controls. The spiked TCA and IBMP samples were not significantly different from the control in either case. Judges were better able to detect compounds if they had prior experience or training in wine evaluation. Despite some limitations, this pragmatic approach may be useful when carrying out sensory studies with fairly limited resources and within tight timelines, as it provides helpful information on panel members and detection thresholds for a specific matrix. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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10 pages, 1050 KiB

Open AccessArticle

Measuring Thiols in Single Cultivar South African Red Wines Using 4,4-Dithiodipyridine (DTDP) Derivatization and Ultraperformance Convergence Chromatography-Tandem Mass Spectrometry

by Mpho Mafata, Maria A. Stander, Baptiste Thomachot and Astrid Buica

Foods 2018, 7(9), 138; https://doi.org/10.3390/foods7090138 - 30 Aug 2018

Cited by 19 | Viewed by 5934

Abstract

Wine varietal thiols are important contributors to wine aroma. The chemical nature of thiols makes them difficult to measure due to low concentrations, high sensitivity to oxidation, and low ionization. Methods for the measurement of thiols usually consist of multiple steps of sample [...] Read more.

Wine varietal thiols are important contributors to wine aroma. The chemical nature of thiols makes them difficult to measure due to low concentrations, high sensitivity to oxidation, and low ionization. Methods for the measurement of thiols usually consist of multiple steps of sample preparation followed by instrumental measurement. Studies have collected large datasets of thiols in white wine but not in red wine, due to the lack of availability of suitable methods. In this study, for the first time, convergence chromatography was used to measure thiols in red wine at ultratrace levels with improved sensitivity compared to previous methods. Performance parameters (selectivity, linearity, limits of detection, precision, accuracy) were tested to demonstrate the suitability of the method for the proposed application. Red wine thiols were measured in South African Pinotage, Shiraz, and Cabernet Sauvignon wines (n = 16 each). Cultivar differentiation using the thiol profile was demonstrated. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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17 pages, 1621 KiB

Open AccessArticle

SPME Method Optimized by Box-Behnken Design for Impact Odorants in Reduced Alcohol Wines

by Bithika Saha, Rocco Longo, Peter Torley, Anthony Saliba and Leigh Schmidtke

Foods 2018, 7(8), 127; https://doi.org/10.3390/foods7080127 - 10 Aug 2018

Cited by 15 | Viewed by 6309

Abstract

The important sampling parameters of a headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) procedure such as the extraction temperature, extraction time, and sample volume were optimized to quantify 23 important impact odorants in reduced alcohol red and white wines. A three-factor design of Box-Behnken [...] Read more.

The important sampling parameters of a headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) procedure such as the extraction temperature, extraction time, and sample volume were optimized to quantify 23 important impact odorants in reduced alcohol red and white wines. A three-factor design of Box-Behnken experiments was used to determine the optimized sampling conditions for each analyte, and a global optimized condition at every ethanol concentration of interest determined using a desirability function that accounts for a low signal response for compounds. Shiraz and Chardonnay wines were dealcoholized from 13.7 and 12.2% v/v ethanol respectively, to 8 and 5% v/v, using a commercially available membrane-based technology. A sample set of the reduced alcohol wines were also reconstituted to their natural ethanol level to evaluate the effect of the ethanol content reduction on volatile composition. The three-factor Box-Behnken experiment ensured an accurate determination of the headspace concentration of each compound at each ethanol concentration, allowing comparisons between wines at varying ethanol levels to be made. Overall, the results showed that the main effect of extraction temperature was considered the most critical factor when studying the equilibrium of reduced alcohol wine impact odorants. The impact of ethanol reduction upon the concentration of volatile compounds clearly resulted in losses of impact odorants from the wines. The concentration of most analytes decreased with dealcoholization compared to that of the natural samples. Significant differences were also found between the reconstituted volatile composition and 5% v/v reduced alcohol wines, revealing that the dealcoholization effect is the result of a combination between the type of dealcoholization treatment and reduction in wine ethanol content. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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14 pages, 3069 KiB

Open AccessArticle

Effect of Sulfites on Antioxidant Activity, Total Polyphenols, and Flavonoid Measurements in White Wine

by Mirella Nardini and Ivana Garaguso

Foods 2018, 7(3), 35; https://doi.org/10.3390/foods7030035 - 9 Mar 2018

Cited by 20 | Viewed by 10020

Abstract

Polyphenols content and antioxidant activity are directly related to the quality of wine. Wine also contains sulfites, which are added during the winemaking process. The present study aimed to evaluate the effects of sulfites on the assays commonly used to measure the antioxidant [...] Read more.

Polyphenols content and antioxidant activity are directly related to the quality of wine. Wine also contains sulfites, which are added during the winemaking process. The present study aimed to evaluate the effects of sulfites on the assays commonly used to measure the antioxidant activity and polyphenols and flavonoids content of white wines. The effects of sulfites were explored both in the standard assays and in white wine. The addition of sulfites (at 1–10 μg) in the standard assays resulted in a significant, positive interference in the Folin–Ciocalteu’s assay used for polyphenols measurements and in both the Ferric Reducing Antioxidant Power and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation decolorization assays, which were used for antioxidant activity evaluation. A negative interference of sulfites (at 1–20 μg) was observed for the colorimetric aluminium-chloride flavonoids assay. The addition of sulfites to organic white wines (at 25–200 mg/L wine) clearly resulted in a significant overestimation of antioxidant activity and polyphenols content, and in an underestimation of flavonoids concentration. To overcome sulfite interferences, white wines were treated with cross-linked polyvinylpyrrolidone. The total polyphenols content and antioxidant activity measurements obtained after polyvinylpyrrolidone treatment were significantly lower than those obtained in the untreated wines. Flavonoids were expected to be higher after polyvinylpyrrolidone treatment, but were instead found to be lower than for untreated wines, suggesting that in addition to sulfites, other non-phenolic reducing compounds were present in white wine and interfered with the flavonoid assay. In view of our results, we advise that a purification procedure should be applied in order to evaluate the quality of white wine. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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22 pages, 4087 KiB

Open AccessArticle

Free Monoterpene Isomer Profiles of Vitis Vinifera L. cv. White Wines

by Mei Song, Claudio Fuentes, Athena Loos and Elizabeth Tomasino

Foods 2018, 7(2), 27; https://doi.org/10.3390/foods7020027 - 21 Feb 2018

Cited by 20 | Viewed by 6745

Abstract

Monoterpene compounds contribute floral and fruity characters to wine and are desired by grape growers and winemakers for many white wines. However, monoterpene isomers, especially monoterpene enantiomers, have been little explored. It is possible to identify and quantitate 17 monoterpene isomers in 148 [...] Read more.

Monoterpene compounds contribute floral and fruity characters to wine and are desired by grape growers and winemakers for many white wines. However, monoterpene isomers, especially monoterpene enantiomers, have been little explored. It is possible to identify and quantitate 17 monoterpene isomers in 148 varietal wines from eight grape varieties; Chardonnay, Gewürztraminer, Muscat, Pinot gris, Riesling, Sauvignon blanc, Torrontes, and Viognier in two vintages by Headspace solidphase microextraction multidimensional gas chromatography mass spectrometry (HS-SPME-MDGC-MS). Results obtained from general linear models and discriminant analysis showed significant differences for the isomer profiles and enantiomer fractions among the eight grape varieties and four wine styles. The high R² values from the fitted line show low variation in enantiomeric differences based on variety. These results provide an overview of the monoterpene isomers of wide varietal wines, and support that isomer profiles and enantiomer fractions could differentiate our wines by varietal and wine style. Full article

(This article belongs to the Special Issue Wine Composition and Quality Analysis)

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