Am Sparrow

Effect of grape bunch sunlight exposure and UV radiation on phenolics and volatile composition of Vitis vinifera L. cv. Pinot noir wine

The effect of canopy leaf removal and ultraviolet (UV) on Pinot noir grape and wine composition was investigated in this study. Limited basal leaf removal in the fruit zone was conducted, compared to shaded bunches. The UV exposure was controlled using polycarbonate screens to block UV radiation, and acrylic screens to pass the UV. The results showed that bunch sunlight and UV exposure significantly increased the Brix and pH in the grape juice, and increased substantially wine colour density, anthocyanins, total pigment, total phenolics and tannin content. Bunch sunlight and UV exposure affected terpene alcohols, C13-norisprenoids and other volatile composition of the wine differently. Sunlight exposure and UV resulted in increase of nerol, geraniol and citronellol but not linalool. Sunlight exposure slightly increased the concentration of β-ionone, but the increase was not statistically significant for UV treatment. Neither sunlight nor UV treatment showed any impact on the concentration of β-damascenone.

Pinot Noir wine composition from different vine vigour zones classified by remote imaging technology

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.

Skin Particle Size Affects the Phenolic Attributes of Pinot noir Wine: Proof of Concept

Modifying phenolic composition can improve the quality of Pinot noir wines and overcome common challenges associated with deficiencies in color, tannin, and aging potential. During fermentation, extraction of desirable components from the skin takes place primarily through the inner skin surface of the berry and from broken skin edges. Ostensibly, the extraction of phenolic compounds located in the skin may be enhanced by reducing the skin particle size. Theoretical analysis indicated that moderate fragmentation substantially decreased the surface area to perimeter ratio of grape skins. Three experiments showed that cutting grape skins into smaller fragments facilitated egress of color and tannin from the skin into the wine matrix. In each case, the treatment in which grapes were cut was compared with a crushed berry control made using conventional methods. Homogenization of berry tissues increased tannin concentration by 6-fold, stable pigment concentration by 45%, wine color density by 25%, and blue-purple coloration by 20% in wines at six months bottle age. Undifferentiated cutting of grapes increased tannin by 6.5-fold, stable pigment concentration by 70%, wine color density by 60%, and blue-purple coloration by 10%. A cutting technique that reduced grape skins to 6% of their original size without damaging the seeds produced wines that had 3-fold higher tannin concentration, 95% higher stable pigment concentration, 50% greater wine color density, and 20% increase in blue-purple coloration. The effects of reducing skin particle size on phenolic extraction were found to be much greater than those achieved using pectolytic enzymes. This innovative skin fragmentation technique has the potential to increase skin-derived red wine phenolics and is a viable alternative to maceration techniques currently used during winemaking.

Interactions of Grape Skin, Seed, and Pulp on Tannin and Anthocyanin Extraction in Pinot noir Wines

Berry tissue components (skin, seed, and pulp) were isolated from Pinot noir grapes to determine the tannin content of each component. In addition, the role of each berry component in determining the phenolic profile of the wine was investigated by omitting or doubling each berry tissue in the must and fermenting these using submerged cap microvinification. Monomeric anthocyanin, total tannin, and nonbleachable pigment concentrations in juice and wine were examined at seven time intervals from yeast inoculation (day 0) to 12-months bottle age (day 400). When included in the must, berry pulp was associated with reduced wine tannin concentration, an effect that was more selective for seed tannin. Consequently, the tannin composition of wines made with whole-berry fermentations most closely reflected that of skin tannin. The formation of nonbleachable pigments was greater in treatments where seeds were present during fermentation. However, when the contribution of seed tannin in wine was increased by doubling the complement of seeds in the must, anthocyanin concentration remained constant and the concentration of nonbleachable pigments did not increase during aging. Treatments with a double complement of grape skins were found to enhance both nonbleachable pigment and tannin in aged wines.

Accentuated Cut Edges (ACE): Effects of Skin Fragmentation on the Composition and Sensory Attributes of Pinot noir Wines

The phenolic composition, aroma, and sensory profiles were evaluated for Pinot noir wines made using four different maceration techniques that modified the floating pomace cap during fermentation: 1) daily plunging; 2) reduced skin particle size (accentuated cut edges, ACE); 3) submerged cap; and 4) ACE plus submerged cap. Throughout vinification, wines were analyzed using rapid analytical techniques to assess the following phenolic attributes: anthocyanin, tannin, nonbleachable pigments, color density, and hue. At six months bottle age (230 days postinoculation), sensory and aroma analyses were conducted on the finished wines. ACE macerated wines were found to have the highest proportion of red color, tannin, nonbleachable pigments, fruit and floral aromas, bitterness, and astringency. Submerging the pomace cap resulted in a lower concentration of phenolic components when compared to ACE wines, but resulted in a significantly higher phenolic content and dark cherry aromas and flavor when compared to the control wine. These findings suggest that the employment of either maceration technique has the potential to make a considerable difference to the wine style produced from a given parcel of fruit and may provide an opportunity to press wines earlier in the fermentation. Linear regression analyses were conducted to compare descriptive wine parameters with instrumental phenolic measurements and demonstrated several strong correlations: red color appearance was correlated with both color density (r2 = 0.95) and nonbleachable pigment (r2 = 0.95); dark fruit flavor was correlated with both color density (r2 = 0.85) and nonbleachable pigment (r2 = 0.85); and astringency was correlated with both tannin (r2 = 0.97) and nonbleachable pigment (r2 = 0.87), demonstrating that techniques of rapid chemical analysis were able to provide valuable insights into the sensory properties of the wine and may become useful tools for monitoring the development of the wine during vinification. While submerged cap vinification also increased the tannin and nonbleachable pigment profiles of the wine, ACE maceration was found to be significantly more effective and is likely to be more readily adapted for application in commercial wineries.

Fermentation volume studies for red wine experimentation

Experimental vinification is often used to evaluate changes in viticultural and oenological practices in research trials. Microvinification procedures are used to overcome constraints that make standardised comparisons in commercial wineries difficult. Prior to 2009, a dedicated micro-winery research facility in northern Tasmania used conventional 12 L volume ferments that provided sufficient wine for both sensory and chemical analysis. Since then, much smaller ferment volumes of 1.5 L and of 250 mL have been introduced, and these provide a sufficient sample size for the chemical analysis of phenolic components in the wine. This study reports a comparison of the phenolic attributes of Pinot Noir wines in a replicated trial using must weights of 0.2, 1.0 and 10 kg fermented in vessels of volume 250 mL, 1.5 L and 20 L respectively. Using the same parcel of fruit, a single larger ferment of 330 kg and a vessel volume of 780 L was conducted concurrently. At bottling, six weeks after the end of fermentation, there was no significant difference in the phenolic composition of the wine made from grape musts with a mass of 0.2, 1.0 or 10 kilograms in the replicated trial, and the results were consistent with those for the 330 kg ferment size. We therefore have confidence in using small micro-scale fermenters, which greatly enhance research capability.

Pinot noir Wine Processing and Quality Improved by Skin Fragmentation

Summary Goals: During vintage 2013, the option of using fragmented grape skins for Accentuated Cut Edges (ACE) maceration to improve the phenolic profile of Pinot noir was evaluated at commercial wineries. Subsequently, a small-scale vinification trial was conducted in 2014 to determine whether the enhanced extraction of grape skin components during the first few days of ACE treatment was sufficient to allow grape solids to be pressed from the fermenting wine early, without compromising wine quality. In the following year, commercial trials were conducted to appraise processing efficiency and quality parameters for ACE and Pressed Early Accentuated Cut Edge (PEACE) treated wines. Key Findings: Commercial evaluation of the ACE maceration technique showed improvement in wine color density and stable pigment compared to conventionally made wine. Small-scale and commercial vinification demonstrated substantial benefits when ACE-treated wines were pressed early to make PEACE wines. Discriminative analyses showed clear sensory differences between conventional, ACE, and PEACE-treated wines: the tasting panel preferred ACE and PEACE for color, fruit characters, and structure. Participants at an international tasting workshop favored the PEACE and ACE wines over conventionally made wine by a ratio of six to one. Impact and Significance: Commercial evaluation of ACE maceration and its refinement, PEACE maceration, confirmed that these two new techniques are viable and important winemaking options for the commercial sector, with the potential to reduce processing time and space and labor requirements in the winery. Sensory properties of wines made using ACE and PEACE techniques were found to be favorable, with phenolic quality parameters maintained or improved relative to conventional treatments.