The methyl cellulose precipitable (MCP) tannin assay and a modified version of the Somers and Evans color assay were adapted to high-throughput (HTP) analysis. To improve efficiency of the MCP tannin ...assay, a miniaturized 1 mL format and a HTP format using 96 well plates were developed. The Somers color assay was modified to allow the standardization of pH and ethanol concentrations of wine samples in a simple one-step dilution with a buffer solution, thus removing inconsistencies between wine matrices prior to analysis and allowing for its adaptation to a HTP format. Validation studies showed that all new formats were efficient, and results were reproducible and analogous to the original formats. Keywords: Tannins; anthocyanins; quantification; grape; red wine; wine color; assay; methyl cellulose precipitation
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•Demonstrates the impact of tannin supplements on wine color stability.•In six months, 20% more grape skins increased stable pigment concentration by 40%.•Up to 85% of anthocyanin ...from recycled grape skins retained as stable wine pigments.•Color benefit of grape skin supplement compromised when seed equivalent included.
A particular challenge to making wine from Pinot noir grapes is the delicate flavor, light color and poor ageing potential of the wine. Conventional Pinot noir must preparations were compared with those made using a skin-based supplement to assess the impact on non-bleachable (sulfur resistant) pigments in the wine. When supplemented with either fresh grape pomace of Pinot noir, Pinot gris or Chardonnay grapes; Pinot noir grape marc or a commercial liquid grape skin extract, the additional seeds and pulp from the supplements were shown to compromise the development of stable pigments in the wine. To compare the relative merits of tannin derived from grape skins and seeds, the supplements used in a parallel experiment were the skins alone of the same three grape varieties and at six months bottle age, the stable pigment concentration was found to exceed the amount attributable to the supplement. A third experiment used fermented grape skins as the supplement, with 85% of the supplementary anthocyanin recovered as stable pigment complexes in the wine. Notably, this series of experiments showed that supplements containing grape seeds appeared to compromise non-bleachable pigment formation in the wine while skin only supplements stimulated their development.
Terroir is an important concept linking sensory attributes to geographically specific environmental conditions. Whilst typically applied to wine, the concept of terroir could be applied to cider. To ...investigate the influence of the production region on base cider total phenolic content and sensory attributes, ciders were made using ‘Fuji’ apples sourced from three major apple growing regions in Australia. Total Phenolic Content was measured using a spectrophotometry method recently validated for use in cider. A trained panel performed descriptive sensory analysis by scoring the intensity of 12 pre-determined attributes across the ciders. The intensity of sensory attributes were found to vary significantly between regions. For instance, cider made from apples grown in Stanthorpe was scored significantly higher than ciders made from apples sourced from Batlow and Huon Valley for the attribute ‘Alcoholic’. Cider made with apples from Batlow was scored significantly higher for the attribute ‘Yeasty’ compared to cider made using apples from the Huon Valley. Cider made with apples from Stanthorpe had significantly greater total phenolic content, titratable acidity, sugar content and alcohol by volume than the two other locations. These results suggest that terroir can influence apple cider, as ciders were able to be differentiated by sensory analysis based on the geographical region from where the apples were grown.
During the fermentation of apple juice, yeast metabolism creates complex biosynthetic pathways which produce a range of compounds responsible for the organoleptic qualities of cider. In this study, ...basic cider quality parameters were measured to investigate the influence of six yeast strains on cider made from three apple varieties (‘Pink Lady’, ‘Sturmer’, and ‘Bulmer’s Norman’). Measurement of pH, titratable acidity, and total phenolic content revealed that yeast can influence cider attributes, albeit variety and season dependent. Descriptive sensory analysis using a trained sensory panel was conducted on cider made from ‘Pink Lady’ apples and the same six yeast strains. The sensory panel significantly differentiated the yeast strains on the attributes of ‘fresh apple’, ‘earthy’ and ‘pear’. Identifying the variety specific influence of individual yeast strains on chemical and sensory characteristics of apple cider will provide cider makers with an enhanced understanding when choosing yeast strains.
•Base ciders were produced from ‘Pink Lady®’, ‘Royal Gala’ and ‘Red Delicious’ apples.•TA of apple must was highest for pre-commercial harvested fruit.•Base cider phenolic content was highest in the ...pre-commercial harvest fruit.•‘Red Delicious’ had the highest total phenolics as determined by spectral analysis.•Growers and cider producers can make informed decisions for target cider attributes.
Varietal base ciders were produced from three varieties of dessert apples (‘Pink Lady®’, ‘Royal Gala’ and ‘Red Delicious’) at pre-commercial, commercial and post-commercial harvest timings. Rapid analytical methods were used to categorise the base ciders, and data analysed using principal component analysis (PCA). The titratable acidity of apple must was significantly higher for the pre-commercial harvest fruit for both the ‘Royal Gala’ and ‘Red Delicious’ varieties. The base cider phenolic content was highest in the pre-commercial harvest fruit for all varieties. ‘Red Delicious’ had the highest total phenolics as determined by spectral analysis and supported by the classification provided by the PCA analysis. The spectral fingerprints of the ciders showed two main peaks at approximately 280nm and 320nm indicating phenolic concentrations. Studies analysing characteristics of dessert apple varieties with relevance for cider production will allow for informed decision making for both apple producers and cider makers.
Samples (n = 620) of homogenized red grape berries were analyzed using a visible and near-infrared (NIR) spectrophotometer (400−2500 nm) in reflectance. The spectra and the analytical data were used ...to develop partial least-squares calibrations to predict dry matter (DM) content and condensed tannins (CT) concentrations. The coefficient of determination in cross-validation and the standard error of cross-validation were 0.92 and 0.83% w/w for DM and 0.86 and 0.46 mg/g epicatechin equivalents for CT, respectively. The standard error in prediction was 1.34% w/w for DM and 0.89 mg/g epicatechin equivalents for CT, respectively. By implementing a NIR spectroscopy method to measure DM and CT in red grape homogenates, we have developed an approach that is suited to large-scale compositional analysis in commercial wine production facilities, as it enables the analysis of large numbers of samples needed to stream batches of fruit. From an economical point of view, the calibration models could be achieved with relatively small data sets. Thus, NIR offers a suitable and efficient tool for the simultaneous measurement of DM and CT in addition to other important parameters in red grape homogenates such as total anthocyanins, total soluble solids, and pH, with minimal sample preparation and low cost.
Extraction and stabilization of wine phenolics can be challenging for wine makers. This study examined how yeast choice affected phenolic outcomes in Pinot noir wine. Five yeast treatments were ...applied in replicated microvinification, and wines were analyzed by UV–visible spectrophotometry. At bottling, yeast treatment Saccharomyces cerevisiae RC212 wine had significantly higher concentrations of total pigment, free anthocyanin, nonbleachable pigment, and total tannin and showed high color density. Some phenolic effects were retained at 6 months’ bottle age, and RC212 and S. cerevisae EC1118 wines showed increased mean nonbleachable pigment concentrations. Wine tannin composition analysis showed three treatments were associated with a higher percentage of trihydroxylated subunits (skin tannin indicator). A high degree of tannin polymerization was observed in wines made with RC212 and Torulaspora delbruekii, whereas tannin size by gel permeation chromatography was higher only in the RC212 wines. The results emphasize the importance of yeast strain choice for optimizing Pinot noir wine phenolics.
Measuring chemical composition is a common approach to support decisions about allocating foods and beverages to grades related to market value. Red wine is a particularly complex beverage, and ...multiple compositional attributes are needed to account for its sensory properties, including measurement of key phenolic components such as anthocyanins, total phenolics, and tannin, which are related to color and astringency. Color has been shown to relate positively to red wine grade; however, little research has been presented that explores the relationship between astringency-related components such as total phenolic or tannin concentration and wine grade. The aim of this research has been to investigate the relationship between the wine grade allocations of commercial wineries and total phenolic and tannin concentrations, respectively, in Australian Shiraz and Cabernet Sauvignon wines. Total phenolic and tannin concentrations were determined using the methyl cellulose precipitable (MCP) tannin assay and then compared to wine grade allocations made by winemaker panels during the companies’ postvintage allocation process. Data were collected from wines produced by one Australian wine company over the 2005, 2006, and 2007 vintages and by a further two companies in 2007 (total wines = 1643). Statistical analysis revealed a positive trend toward higher wine grade allocation and wines that had higher concentrations of both total phenolics and tannin, respectively. This research demonstrates that for these companies, in general, Cabernet Sauvignon and Shiraz wines allocated to higher market value grades have higher total phenolics and higher tannin concentrations and suggests that these compositional parameters should be considered in the development of future multiparameter decision support systems for relevant commercial red wine grading processes. In addition, both tannin and total phenolics would ideally be included because although, in general, a positive relationship exists between the two parameters, this relationship does not hold for all wine styles.
•We can delineate vine vigor zones using remote sensing technology.•Ultra low vigor zone wines had the highest concentrations of esters and alcohols.•Low vigor zone wines had higher linalool, nerol ...and geraniol but not citronellol.•Lower vigor zone wines had higher vitispirane and β-ionone.•There was no obvious trend for β-damascenone among the vigor zones.
The relationship between grapevine vigour and grape and wine composition was investigated in this study. Own-rooted Pinot Noir grapevines were grown in a commercial vineyard in Tasmania, Australia, with uniform vineyard management practices. Vine vigours were determined by plant cell density (PCD) obtained from aerial photography. As vine vigour decreased, total soluble solid in grapes, total phenolics and anthocyanins in wines increased, while titratable acidity and yield decreased. Wines from the ultra low vine vigour zone had the highest concentrations of esters and alcohols. Higher level of linalool, nerol, geraniol, vitispirane, and β-ionone were observed in ultra low vigour and low vigour zones, but there was no obvious trend for citronellol and β-damascenone. Principal component analysis and discriminant analysis of the volatiles illustrated the differences among wines from the four vine vigour zones.
This study outlines the use of mid-infrared (MIR) spectroscopy combined with principal component analysis (PCA) and linear discriminant analysis (LDA) for the varietal classification of commercial ...red and white table wines. Three red varieties (Cabernet Sauvignon, Shiraz and Merlot) and four white varieties (Chardonnay, Riesling, Sauvignon Blanc and Viognier) were sourced from different wine regions in Australia. Wine samples were scanned in transmission on a FOSS WineScan FT 120 from wave numbers 926 to 5012
cm
−1. All samples were sourced from the 2006 vintage and had not been blended with any other variety or wine from other regions. Spectral data were reduced to a small number of principal components (PCs) and LDA was then performed to successfully separate the wines into the different varieties. To test the robustness of the LDA models developed for the red wines, a set of red wines scanned in 2005 were used. Correct classification of over 95% was achieved for the validation set.
