New Formulations of Fungicide May Alter Sensory Characteristics in White Wine

Fungicides are frequently used in viticulture to treat and prevent various diseases such grey mould (Botrytis cinerea), powdery mildew (Erisiphe necator), and downy mildew (Plasmopara viticola).  New formulations of fungicides are currently being tested to replace older, more controversial applications, which may provide similar if not better protection than the older methods.  Active ingredients considered in the new formulations include benalaxyl, benalaxyl-M, boscalid, cyazofamid, famoxadone, fenamidone, fluquinconazole, iprovalicarb, metrafenone, proquinazid, pyraclostrobin, trifloxystrobin, valifenalate, and zoxmide.

http://www.apsnet.org/edcenter/intropp/ lessons/fungi/Oomycetes/Article%20Images/ DownyMildewGrape09.jpg

After application of the fungicide, the residues are able to seep across the skin of the grape which can pass through the winemaking process and potentially alter the quality of the final wine.  Some research has shown that fungicide residues are responsible for slowly down or stopping alcoholic fermentation all together, which was found to be due to negative effects on the yeast and bacteria used in the process.  Other research has shown that these negative effects on alcoholic fermentation of grapes exposed to fungicide treatment can alter the chemical components of the wine, thus altering the phenolic composition and sensory characteristics.

The study presented today sought to examine the influence of new formulations of fungicides on the synthesis of volatile compounds in wine, as well as the sensory characteristics and overall quality.

Methods

The experiments performed for this study were field trials located in Ribadavia, in Galicia, northwest Spain (2009 vintage) at a vineyard producing white grapes (Vitis vinifera Godello cv). The vineyard plot was 2000m², which was divided into 12 rows with 35-40 vines per row.  Vines were spaced 1m apart, with 1.8m between rows.  Vines were 10 years old and were trained on a double cordon trellis.  Different treatments were applied to control for downy mildew, powdery mildew, and grey mould.  Rows were divided randomly into four plots (A, B, C, and D).  Then, different phytosanitary treatments were carried out in each plot.  9 applications were performed, at different phenological stages, using a M-83-E hand-gun sprayer.

For downy mildew, the following treatments were used:

·         Cabrio Top (55% metiram + 5% pyraclostrobin) and Fobeci (35% folpet + 6% benalaxyl + 3.2% cymoxanil) (applied in May)

·         Mandipropamid was applied as an active substance in plot A.

·         IR-5885 (6% valifenalate + 60% mancozeb) was applied in plot B.

·         Mildicut (2.5% cyazofamid) and Equation Pro (22.5% famoxadone + 30% cymoxanil) were applied to plots C and D, respectively.

·         The last application of all treatments was 3 days before harvest

·         Rows 11 and 12 were left untreated during the final application to serve as the control.

For powdery mildew and grey mould:

·         5 applications for powdery mildew treatment :

·         Talendo (20% proquinazid) was applied to plots A and D.

·         Vivando (50% metrafenone) was applied to plots B and C.

·         2 treatments for grey mould, 1 application each:

·         Cantus (50% boscalid) was applied to all plots.

·         Switch (37.5% cyprodinil + 25% fludioxonil) was applied to all plots.

Grapes were harvested in September, and at least 15 randomly selected bunch samples from each plot were used for analysis.

Single vinifications were performed, and there were no repetitions/replications.  Standard vinification techniques were used (I can provide details if you need them: just ask!).

After bottling, the following parameters were measured: pH, alcoholic degree, total maximum real acidity, total maximum sulfur.

Fungicide residues were measured using solid phase extraction clean-up, and by gas chromatography analysis.

Wines were tested in a sensory analysis for quality (color, aroma, taste, and mouth feel) by 7 trained/experienced panelists from the Valdeorras appellation in Spain.

Results

Fungicide Residues in Grape Samples after Harvest

            Control of Downy Mildew:

•       Residues of benalaxyl, cymoxanil, folpet, and pyraclostrobin were not detected in grapes, except for plot D (which had later applications of Equation Pro).
•       Applications of mandipropamid in plot A showed residual concentrations in grapes that was lower than maximum levels allowed established by the European Union.
•       Applications of mandipropamid in plots B, C, and D showed residual concentrations in grapes that was higher than maximum levels allowed established by the European Union.
•       Applications of IR-5885 in plot B showed residual concentrations of valifenalate in grapes that was higher than maximum levels allowed established by the European Union.
•       Applications of Mildicut in plot C showed residual concentrations of cyazofamid in grapes that was higher than maximum levels allowed established by the European Union.
•       Applications of Equation Pro in plot D showed residual concentrations of cymoxanil and famoxadone in grapes that was above and close to the maximum levels allowed established by the European Union.

Control of Powdery Mildew:

•       Applications of both Talendo and Vivando in all plots showed residual concentrations of proquinazid and metrafenone in grapes that was below the maximum levels allowed established by the European Union.

Control of Grey Mould:

•       Applications of both Cantus and Switch in all plots showed residual concentrations of boscalid in grapes that was below the maximum levels allowed established by the European Union.

Dissipation after Winemaking?

•       After the white winemaking process, there was a high (90%-99%)  dissipation of fungicide residues initially detected, with the exception of valifenalate, which only had 32% dissipation. 

Sensory Analysis

•       6 sensory attributes were significantly different between the wines created by grapes treated with different fungicide treatments and the control:

o   Odor intensity, apricot and floral odors, and flavor intensity were lower in wine A (from plot A) than the control.

o   Apricot and floral odors were lower in wine B (from plot B) than the control.

o   Color and odor intensity were higher, and apricot and floral odors were lower in wines C and D (from plots C and D) than the control.

o   The acidity from wine C was higher than wine D, with the control wine acidity falling in between the two.

•       Summary of results after many statistical analysis and tests:

o   There was a predominance of floral odors (with a distinct apricot odor) in wines made from grapes treated with downy mildew fungicides.

o   Quality was related to the balance of odors, and acidity levels.

o   Odor fineness was negatively correlated with a bitter taste.

o   Limpidness was positively associated with melon notes.

o   Viscosity was associated with tropical and Mediterranean fruit odors.

o   Odor intensity and persistent flavors were associated with citrus and herbaceous odors.

o   Bitterness was associated with green apple odors.

o   Overall quality was associated with dryness, smoothness, acidity and fruit tastes, and flavor intensity.

o   In summary, higher levels of fungicide residues result in higher color shades, higher tropical fruit odors, and higher sweet tastes.

In Summary

The new fungicide formulas tested resulted in fungicide residues in grapes that were close to or higher than levels currently allowed by the European Union.  Even though the majority of these fungicides dissipated after the white winemaking process, the exposure was ample enough to alter the flavor characteristics of the final wine. 

One problem I have with the result is that there was only one wine made per plot (no replication).  It is not completely clear if the results found were because of any particular fungicide treatment, or because of a difference in that particular batch of winemaking.  I’d like to see more replication by these and other authors, to be completely certain of the results.

It was also not clear to me whether the finished wines were poorer in quality than the controls, or if they simply just tasted different.  Different taste doesn’t necessarily mean poorer quality, so I am hesitant to draw any conclusions as to which fungicide treatment would be the best option.

What do you think of the results?  Are you seeing something in these results that I missed?  Feel free to leave any comments below.

Source: González Álvarez, M., Noguerol-Pato, R., González-Barreiro, C., Cancho-Grande, B., and Simal-Gándara, J. 2012. Changes in the sensorial attributes of white wines with the application of new anti-mildew fungicides under critical agricultural practices. Food Chemistry 130: 139-146.

DOI: 10.1016/j.foodchem.2011.07.018

I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!