The aim of the study was to investigate to what extent winemaking supplements can alter the sensory properties of Shiraz wines from grapes picked at lower sugar levels to more closely resemble wines from grapes from the same vineyard, picked at higher sugar levels.
Project layout
- Shiraz grapes were harvested at two sugar levels: 23.9°Brix (A) and 27.7°Brix (B), from a commercial vineyard in McLaren Vale, Australia.
- The wines were fermented with Lalvin EC 1118 at 28°C.
- Harvest A wines underwent seven different treatments: control, cold soak, enzyme addition, enzyme + mannoprotein (MP) addition, tannin addition, tannin + MP and MP alone. Laffort products: Lafase HE Grand Cru, VR Supra + VR Color and Oenolees MP were use in the trial. Details of dosages and timing of addition can be obtained from the scientific publication.
- Harvest B underwent no treatments and served as the control wine made from grapes with a high sugar level.
- Basic, polyphenolic, polysaccharide and sensory descriptive analyses were performed on the wines three months after the completion of fermentation.
Results
Please refer to the publication for all results obtained. Some of the more significant results include:
- Wine made from the riper grapes were naturally higher in colour, tannin, mannoproteins, dark fruit aroma, flavour intensity, jammy character, sweetness, palate fullness and hotness than the lower sugar wine control with no supplements.
- Cold soak slightly increased red and dark fruit aromas but had no effect on anthocyanin and tannin concentrations.
- Enzyme addition + cold soak increased red fruit aroma, slightly increased flavour intensity and decreased jammy character compared to control.
- Enzyme addition significantly enhanced tannin concentration in harvest A wines. Although tannin levels were similar to harvest B wine, the matrix effect of the harvest B wine softened the astringency associated with higher tannin concentration.
- Enzyme treated wines had significant increased levels of free monosaccharides, especially galacturonic acid and arabinose, indicating the high efficiency of this enzyme to break down pectin.
- Mannoprotein treatment decreased tannin concentration and astringency mouthfeel.
- Mannoprotein + enzyme addition treatment was similar to enzyme treatment alone.
- In this trial the tannin addition had no effect on anthocyanin and tannin concentration, but had a significant effect on the sensory properties of the final wines.
- Compared to the control, tannin addition increased the red fruit aroma and decreased the dark fruit aroma and jammy character.
- Tannin + MP addition increased the dark fruit aromas compared to the control and cold soaked wines.
Significance of the study
This study indicates that the use of supplements during or after fermentation can alter the final wine’s polyphenolic, polysaccharide and sensory properties significantly. Whether a particular supplement will be effective, or not, depends on the specific wine matrix, as well as the nature of the products used (differences between suppliers’ offerings). Combining more than one treatment may not necessarily lead to a cumulative effect. This research investigated one supplier’s products on one grape variety. Winemakers are encouraged to trial these type of products, to first ensure that it will have a desired effect before purchasing on large scale. Used correctly according to manufacturers’ recommendations and where applicable, winemaking products can improve wine characteristics significantly (financial/reputation gain). Used incorrectly and without proper trialing first, can lead to no result or a negative result in terms of wine character (financial loss).
Reference
Sijing Li, Keren Bindon, Susan E. P. Bastian, Vladimir Jiranek, and Kerry L. Wilkinson. Use of winemaking supplements to modify the composition and sensory properties of Shiraz wine. Journal of Agricultural and Food Chemistry 2017 65 (7), 1353-1364. DOI: 10.1021/acs.jafc.6b04505
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