No Sulfur Winemaking in Chardonnay (2017)

This study examines the effect of fermenting wine with and without sulfur dioxide. Chardonnay grapes were harvested and pressed into 3 separate tanks. At pressing, one treatment received 3g/hL sulfur dioxide (control), and the other did not receive any sulfur dioxide, and the third did not receive any sulfur dioxide and received Stab Micro M and Tan Blanc at pressing and followed an Enartis no sulfur winemaking protocol. After settling, the juices were racked into barrel and inoculated with CY 3079. The Enartis wine received additions of Claril SP during settling. After completion of malolactic conversion, the control wine was stabilized with sulfur dioxide, and the Enartis treatment had Stab SLI, Tan SLI, and Stab Micro added at the end of malolactic conversion. Both barrels with the Enartis treatment fermented slower than the rest. No major chemistry differences were found between wines except for slightly lower lactic acid in the Enartis wine. The no sulfur wine had slightly higher levels of Lactic Acid Bacteria, slightly less O. oeni, and slightly less S. cerevisiae. The Enartis wine had slightly more S. cerevisiae, and slightly higher diacetyl. In general, judges were able to distinguish between the wine made with and without sulfur dioxide. This may have been due to a perceptible difference in diacetyl between these two wines, likely due to diacetyl binding by sulfur dioxide in the wine produced with sulfur dioxide. The no sulfur wine treatment may have had slight oxidation (but not in a negative respect), and the Enartis no sulfur wine may have had a slight bitterness (although this was not examined statistically). A perceived bitterness in the Enartis wine may be due to the use of sacrificial tannin. Preferences were not strong, but there seemed to be a preference for the wine made with sulfur dioxide, and then perhaps followed by the wine made without sulfur dioxide. However, many more studies are needed to further qualify how no sulfur winemaking impacts wine sensory qualities. Additionally, more studies need to be performed to determine how no sulfur wines age over time.

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No Sulfur Winemaking in Cabernet Franc (2017)

This study examines the effect of producing wine with and without sulfur dioxide. Cabernet Franc grapes were harvested and processed into 3 separate T Bins. During crush, one treatment received 25ppm sulfur dioxide (control), the second did not receive any sulfur dioxide but instead was protected at crush with Zymaflore Egide, and the third did not receive any sulfur dioxide but instead received Tan Rouge and Stab Micro M during crushing and followed an Enartis no sulfur winemaking protocol. After processing, all wines were inoculated with ES488. One-third through fermentation the Enartis treatment received additions of Pro Tinto and Tan Color. Both no sulfur treatments were inoculated with ML Silver after pressing. At the end of fermentation, the control wine was stabilized with sulfur dioxide, the no sulfur wine received Stab Micro, and the Enartis protocol received additions of Surli Round, Tan SLI, and Stab Micro M. Wine chemistry is similar between treatments, except that no sulfur winemaking resulted in slightly lower TA. Both no sulfur winemaking wines had higher levels of acetic acid bacteria, lactic acid bacteria, and Pediococcus. Color intensity was higher due to a lack of sulfite bleaching. Overall, Cabernet Franc produced with sulfur dioxide tended to have higher perceived Acidity. Other differences between wines were not easy to distinguish with the descriptors used in this study, but the no sulfur wine and the wine with sulfur dioxide may have had slightly higher Overall Aromatic Intensity and Fruit Intensity. The wine made with sulfur dioxide tended to be most preferred, followed by the wine without sulfur dioxide. Conclusions are difficult to draw at this point. Many more studies are needed on no sulfur winemaking in red wines and its impact on sensory qualities. Additionally, more studies are needed to examine how aging is affected by no sulfur winemaking.

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Yeast Strain Selection to Produce Sulfur Dioxide-Free Merlot Wine (2017)

This study examines the efficacy of non-Saccharomyces yeast selection to produce wines without the use of sulfur dioxide. Merlot grapes were harvested on September 28 and stored overnight at 45°F. The next day fruit was destemmed, sorted, and crushed into two separate bins (0.5 tons per treatment). One bin received 6g/hL sulfur dioxide (control), and the other received 5g/hL Primaflora VR Bio (AEB) as a sulfur dioxide replacement (no sulfur dioxide treatment). Both bins received a two day cold soak (one punchdown per day, with dry ice additions), and then the control bin received 15g/hL FX10, and the treatment received 15g/hL FX10. At this point the bins were moved out of the cold room in order to warm up. Punchdowns were twice per day until fermentation became vigorous (October 6), which then received 3 punchdowns per day. Fermentation lasted for 8 days, after which the wine was drained off the skins and put into stainless steel tanks for aging (only free run was used). On November 30, wines were filtered with K250/EK filters and sterile filtered (0.45 micron) and bottled on December 7. At bottling, the control received 1g/hL sulfur dioxide. The wine without sulfur dioxide had slightly less alcohol and lactic acid, and slightly increased volatile acidity. It also had less color and had a slightly longer lag phase in fermentation. The no sulfur dioxide wine seemed to have more yeasts throughout its life except for Hanseniaspora, relative to the control. Both fermentations had similar bacterial counts. Overall, judges were more or less able to correctly distinguish the wines made with and without sulfur dioxide, although in one tasting this was statistically significant and at the other it was not. Judges tended to prefer the wine made without sulfur dioxide. The no sulfur wine may have had higher Fruit Intensity, higher Overall Aromatic Intensity, and higher perceived Acidity relative to the wine made with sulfur dioxide.

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The Impact of Increased Sulfur Dioxide at Crush on Color and Tannin Extraction (2017)

High concentrations of sulfur dioxide at crush can enhance color extraction during maceration. This study examines the impact of high levels of sulfur dioxide at crush on color and phenolic extraction. Pinot noir from a single vineyard block was sorted, destemmed, and divided into 4 T bins. The T bins received either 50ppm, 100ppm, 150ppm, or 200ppm sulfur dioxide at crush. All other treatments between wines were identical. 150ppm and 200ppm sulfur dioxide seemed to induce a slightly longer lag phase relative to lower levels of sulfur dioxide, but otherwise fermentation kinetics were similar. Wine chemistry was similar between treatments, except that TA and lactic acid decreased slightly with increasing levels of sulfur dioxide. Total, free, and molecular sulfur dioxide increased with increasing concentrations added at crush. Color intensity, anthocyanins, catechin, epicatechin, and tannin all seemed to increase as well from increasing sulfur dioxide usage. Overall, lower rates of sulfur dioxide tended to have higher Fruit Intensity. 100ppm of sulfur dioxide had a strong tendency for the highest Fruit Intensity and lowest Herbaceous/Green character. Body tended to be higher at 100ppm as well. Higher rates of sulfur dioxide addition (above 100ppm) tended to increase Astringency. The perception of Acidity may have been increased by higher sulfur dioxide levels as well. The most preferred wine was the wine produced with 100ppm of sulfur dioxide. More studies should be performed to evaluate the use of sulfur dioxide at crush, particularly with other grape varieties.

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Sulfur Dioxide-Free Winemaking with Merlot (2015)

Merlot was produced using traditional winemaking practices and sulfur dioxide-free winemaking practices.  There were very little chemical differences between the control and low sulfur dioxide treatments.  The traditional method seemed to have a higher microbial presence.  The traditional method seemed to result in higher phenolic extraction (probably due to increased extraction from sulfur dioxide), but higher color intensity was found in the sulfur dioxide-free wine.  This is likely due to less monomeric anthocyanin bleaching.  There was no significant sensory difference (p<0.05) between the traditional and sulfur dioxide-free wine. However, of those that responded correctly (n=13) 69% preferred the control and 31% preferred the trial.

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Low Sulfur Dioxide Winemaking with Viognier (2015)

Viognier was fermented using traditional winemaking and sulfur dioxide-free winemaking at the pressing stage.  Sulfur dioxide was used after the completion of alcoholic fermentation.  The wine produced had very little chemical differences, except that the sulfur dioxide-free wine had much more malic acid.  The traditional wine in general had a slightly higher microbial presence.  Although sensory differences were distinguished between the wines, there was no sensory preferences between the wines.

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