This study compares the effects of destemming and cold soaking Petit Manseng Grapes for 6 hours prior to pressing compared to directly pressing whole clusters. Juice produced with skin contact showed higher pH without much change in TA. The wine which underwent skin contact showed much lower TA and much higher pH. Skin contact also increased color intensity, catechin, tannin, caffeic acid, gallic acid, and astilbin. Caftaric acid was decreased by skin contact. This loss in caftaric acid and gain in caffeic acid could be due to equilibrium pressure. Sensory testing found the wines to be significantly different. Direct to Press wines had a slight tendency for higher Tropical Fruit aromatics, and a strong tendency for these wines to have higher Overall Aromatic Intensity. Skin-Contacted wines had strong tendencies towards increased Bitterness, and a slight tendency for higher Astringency. In general, people tended to prefer wines made from direct pressing. Studies of this kind, in conjunction with phenolic fining studies, should be performed in the future.
This study compares the efficacy of juice clarification with flotation to that of cold settling. The
cold-settled juice fermented slightly slower. No notable chemical differences were apparent between juice and wine, except that cold-settled juice produced wine with a higher degree of cold stability. The TA was higher for the float-clarified wine. Wine produced from flotation resulted in less losses to gross lees, and reduced the need for chiller load. It could potentially reduce turn-around time as well, but this was not characterized fully in this study. A significant difference (p<0.001) between wines was found in triangle testing. Although descriptive analysis showed no strong trends for the descriptors used in this study there was a slight trend for wines produced with flotation to have higher Fruit Intensity as well as Overall Aromatic Intensity. In general, there was not a noticeable preference for the floated wine over the cold settled wine. These results suggest that flotation may be a beneficial technique not only to reduce turn-around time, enhance juice yield, and reduce chiller load; but that it may also serve as a mechanism for preserving aromatic intensity and fruit intensity.
This study compares the effects of fermenting Chardonnay juice at a low turbidity, medium turbidity (110NTU), and high turbidity (225 NTU). Juice from the same pick of Chardonnay was settled and racked into barrels. Turbidity was adjusted by adding back fine lees to the juice. All other treatments between wines were the same. The 110 NTU and 225 NTU wines had no chemical differences. The wines were not found to be statistically different at tastings, and those who were able to correctly distinguish the wines had a slight tendency to prefer the wine made from higher turbidity. This wine had a slight trend to be higher in Overall Aromatic Intensity and lower in Bitterness. More work is needed here to obtain a better understanding of the effect of juice turbidity on wine quality. It may be that the turbidity difference in this study was too small to have a great effect on the wine flavor profile.
This study compares the effects of fermenting Sauvignon Blanc juice at a low (50 NTU) or high turbidity (250 NTU). Juice from the same pick of Sauvignon Blanc was settled and racked into stainless steel barrels. Turbidity was adjusted by adding back fine lees to the juice. All other treatments between wines were the same. No major chemical differences could be found between juice or wine, except that the juice with higher turbidity had slightly higher YAN and its wine had slightly lower alcohol. High turbidity greatly increased 3-mercaptohexanol and 4-methyl-4-mercaptopentan-2-one, but decreased 3-mercaptohexylacetate. Triangle testing suggests that the wines were significantly different (p<0.001). No major preference could be seen for one wine over the other. No major trends could be found for the descriptors used in this study, despite the wines being found to be significantly different. There was a slight tendency for the High NTU wine to have more Varietal Character and Overall Aromatic Intensity, while having less Body.
This study examines the effect of different rosé must processing techniques on the chemical and sensory qualities of finished wine. Merlot grapes were either sent directly to press or cold soaked for two days prior to pressing. After cold soak and pressing, juice was either settled and inoculated or stabulated for approximately 5 days, after which it was inoculated and a Laffort thiolase enzyme was added. Merlot sent directly to press underwent stabulation. Not many chemical differences could be seen between stabulated juices with the control, except a higher initial turbidity. These results suggest that for this particular style of rose winemaking, judges preferred wine made from the two-day cold soak, regardless of stabulation. Although the stabulated and control wines were found to be significantly different, no major trends could be seen for the descriptors used in this study except for perhaps a slight increase in fruit intensity and thiol aromas. No major preference could be seen for the control wine and stabulated wine, suggesting that stabulation can act as a technique to process wine without much altering the flavor profile in a negative matter.
This study examines the effect of adding fining agents to hyperoxidized Petit Manseng juice on the sensory and phenolic characteristics of Petit Manseng. After reducing the temperature to 10-12°C, Petit Manseng juice was hyperoxidized by pumping four volumes of juice over a sump screen, taking about 10 minutes. After this process, juice was very brown and then sulfur dioxide was added at 50ppm. Juice was then split into two vessels, one of which was fined with casein, PVPP, and bentonite to remove solids and phenolic compounds. All other treatments between juices and wines were identical. Overall, no major chemical, color, or phenolic differences were observed between the wines, suggesting that fining juice after hyperoxidation does not do much to alter the color and phenolic properties of the wine. Triangle testing suggests that the wines were significantly different from each other (p<0.001), likely due to a difference in turbidity. No preferences could be seen for one wine over the other. The fined wine had a slight tendency for lower Tropical Fruit and increased Bitterness/Astringency.
The effect of press enzymes Cinn-Free (ScottLabs) and Lafazym Press (Laffort) on finished Sauvignon Blanc wine were compared. There were no chemical differences between the wines except that the Lafazyme-treated juice had a slightly higher titratable acidity. There were no significant sensory differences between the wines, but there seemed to be a slight preference for Lafazyme. No yield comparisons were made.