| 1. |
- Andraous, Johnny I., et al.
(författare)
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Effect of liquefaction enzymes on methanol concentration of distilled fruit spirits
- 2004
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Ingår i: American Journal of Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 55:2, s. 199-201
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Tidskriftsartikel (refereegranskat)abstract
- Liquefaction enzymes are often used during fermentation of fruit mashes to improve the yield of ethanol and the ability to pump the mash. The liquefaction enzymes hydrolyze pectin, but in addition to the desired pectin hydrolysis activity, the enzymes also have pectinesterase activity which hydrolyzes the methyl ester in pectin resulting in methanol formation. Fermentations of various apple varieties and Bartlett pears were conducted using liquefaction enzymes. The resulting distilled products contained concentrations of methanol above the legal limit of 280 mg/100 mL of 40% ethanol, with the observed methanol concentrations in a range between 320 and 656 mg/100 mL of 40% ethanol. In contrast to the undesired increase in methanol concentration, the enzymes provide only a marginal increase in ethanol yield. The results indicate that liquefaction enzymes should be used with caution for pomace fruit and that methanol monitoring should be implemented if these enzymes are used for commercial products.
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| 2. |
- Danner, L., et al.
(författare)
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Dynamic viscosity levels of dry red and white wines and determination of perceived viscosity difference thresholds
- 2019
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Ingår i: American Journal of Enology and Viticulture. - : American Society for Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 70:2, s. 205-211
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Tidskriftsartikel (refereegranskat)abstract
- Wine mouthfeel significantly contributes to the overall sensory perception and quality of wines. However, the influence of dynamic viscosity on the mouthfeel of dry table wines is still not fully understood. The three objectives of this study were to 1) determine the perceived viscosity difference threshold in wine using wine/xanthan gum solutions, 2) measure dynamic viscosity levels of Australian commercial dry Shiraz and Chardonnay table wines, and 3) investigate in wine samples the relationship between dynamic viscosity and chemical parameters, specifically, residual sugar, ethanol, and pH. A wine viscosity difference threshold value of 0.138 mPa·sec at 20°C was determined by ascending two-alternative forced-choice difference threshold tests with a sensory panel (n = 45). The dynamic viscosity for 34 commercial Chardonnay wines at 20°C ranged from 1.448 mPa·sec to 1.529 mPa·sec, and from 1.488 mPa·sec to 1.695 mPa·sec for 29 Shiraz wines. These results indicate that on the basis of the determined threshold values, tasters could likely differentiate wines in terms of viscosity within the viscosity range of this sample set of Shiraz, but not Chardonnay, wines. Furthermore, significant correlations between dynamic viscosity and ethanol concentration, but not for pH and residual sugar, were found for both varieties, indicating that ethanol may have been the main compositional factor that increased dynamic viscosity in commercial dry wines.
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| 3. |
- Jiang, W. W., et al.
(författare)
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Effects of immersive context and wine flavor on consumer wine flavor perception and elicited emotions
- 2017
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Ingår i: American Journal of Enology and Viticulture. - : American Society for Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 68:1
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Tidskriftsartikel (refereegranskat)abstract
- Food studies have shown that emotional responses can be influenced by food alone and by its environmental context. The influence of context on perception and liking of red wine flavors and on the emotions evoked is poorly understood. The primary aim of this research was to examine the effect of wine flavors and context by immersive environment on consumer-perceived intensities of green and floral flavors, liking, and emotions elicited during wine consumption. Red wine consumers (n = 105) tasted three Cabernet Sauvignon wines: an unaltered control wine (CW), green wine (GW; control wine spiked with 3-isobutyl-2-methoxypyrazine), and floral wine (FW; control wine spiked with rose water), in both a “floral” room (FR) and a “green” room (GR). The wine consumers were asked to taste and rate the intensity of green and floral flavors, hedonic liking, and the emotions elicited. The results showed that in both rooms, FW was rated consistently higher in floral flavor and GW was rated higher in green flavor. CW and FW were significantly (p < 0.001) more liked than the GW. Based on wine liking, three clusters were identified. CW and FW evoked significantly higher positive emotions than GW (p < 0.05), while GW evoked significantly higher negative emotions than CW and FW (p < 0.05) in both rooms. The effect of immersive environment did not influence flavor perception, hedonic liking, or emotional responses. Consumers were also separated into three clusters according to their liking of wines tasted, and despite clusters having identical liking for certain wines, the associated emotions differed.
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| 4. |
- Kang, W., et al.
(författare)
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Reduction of red wine astringency perception using vegetable protein fining agents
- 2018
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Ingår i: American Journal of Enology and Viticulture. - : American Society for Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 69:1, s. 22-31
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Tidskriftsartikel (refereegranskat)abstract
- The use of vegetable proteins to fine astringent compounds in wine has gained increased interest due to the pressure of consumer demand. The objective of this study was to compare the ability of alternative vegetable proteins (derived from rice, soy, pea, or potato) to reduce tannin and thereby astringency, relative to that of traditional fining agents (gelatin and polyvinylpolypyrrolidone [PVPP]) in a commercial wine with added grape seed extract. Total tannin and phenolics, SO2-resistant pigments, pH, and color of the treated wines were determined, and astringency intensity perception was evaluated by a trained sensory panel (n = 9). Potato, pea, soy, and gelatin proteins similarly reduced total tannin concentration. Similar to PVPP, addition of rice or soy protein reduced total phenolics. These alternative vegetable proteins also influenced the chroma, which may change the depth of wine color. Furthermore, this study was the first to evaluate the change in astringency sensation resulting from the use of rice and soy proteins as alternative fining agents. The type of vegetable proteins used appeared to fine different types of polyphenolic compounds, an observation that was reflected on astringency perception and requires further investigation. The chemical and sensory measures showed that rice and potato proteins have the potential to replace PVPP and gelatin, respectively.
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| 5. |
- Niimi, Jun, et al.
(författare)
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Linking sensory properties and chemical composition of Vitis vinifera cv. Cabernet Sauvignon grape berries to wine
- 2017
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Ingår i: American Journal of Enology and Viticulture. - : American Society for Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 68:3, s. 357-368
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Tidskriftsartikel (refereegranskat)abstract
- It is conventional wine industry practice for winemakers and grapegrowers to taste winegrapes to determine their fitness for producing various wine styles of different quality. However, the ability to predict wine style from tasting grapes is unverified, and the relationship among the sensory characters of grapes and wine is poorly understood. The objective of the study was to investigate the sensory properties of Cabernet Sauvignon grapes and the corresponding wines, and to determine the relationships between the two data sets. Grapes were harvested between 23 and 25 Brix from eight locations across the state of South Australia over two vintages and vinified using a standardized protocol. A total of 25 samples from across the eight locations were harvested for each vintage. The grapes and wines were evaluated by a sensory panel trained in descriptive analysis. Grapes were evaluated using the berry sensory assessment (BSA) methodology previously described in the literature, and the basic chemical parameters of the grapes and wines were measured. Samples were consistently discriminated by their chemical and sensory properties within the grape and by wine data sets across the vintages. Five sensory attributes of wine were consistently modeled with moderate to high regressions using BSA attributes and berry-chemical measures. Finding berry sensory attributes that consistently relate to wine style and profile remains challenging. The basic chemical measures, including Brix, anthocyanins, and chroma of grape homogenates, were reliable contributors to wine sensory attributes for both vintages.
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| 6. |
- Niimi, Jun, et al.
(författare)
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Linking the sensory properties of chardonnay grape Vitis vinifera cv. Berries to wine characteristics
- 2018
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Ingår i: American Journal of Enology and Viticulture. - : American Society for Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 69:2, s. 113-124
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Tidskriftsartikel (refereegranskat)abstract
- Formal or informal sensory analyses of grapes are often used to determine when a parcel of fruit should be harvested to produce a certain wine style. This study investigated whether relationships exist between sensory perceptions and basic chemical measures of Chardonnay grape berries and the corresponding wines. Chardonnay grape parcels were harvested at commercial maturity from across South Australia in vintages 2015 and 2016, yielding a total of 25 and 24 samples, respectively. Grapes were evaluated using berry sensory assessment (BSA) and vinified identically using small-scale winemaking, and the resulting wines were evaluated with descriptive sensory analysis. Sensory assessors were trained in the respective sensory evaluation methods. Chardonnay grape and wine samples were discriminated by the panel according to sensory attributes, and the fruit could also be discriminated by basic chemistry measures. However, differences in Chardonnay wines were subtle compared with those in grapes, as indicated by low effect sizes. Moderate validation models (R2 Val = 0.53 to 0.81) of partial least squares regression (PLSR) 1 were determined in the 2015 vintage, using BSA attributes as x-variables and wine sensory attributes as y-variables, but poor models were obtained with the 2016 vintage (R2 Val < 0.5). In the 2015 models, relationships were found for wine attributes of heat, sourness, and astringency, possibly due to slight variations in ripeness. Strong relationships that revealed wine style from variations in grapes were not found. Overall, relating the sensory characteristics of Chardonnay grapes to the wines was challenging and indicated that variation in style of these varietal wines does not greatly depend on the raw grape material.
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