Non-Microbial Off Aromas

Transcription

1 Non-Microbial Off Aromas Oxidation Prevention: Reduce oxygen exposure SO 2 Hyper-oxidation (for some whites) Control for metals (Cu, Fe) Enartis Pro FT, other thiols Control for oxidation of phenolic compounds (Glutathione enriched products) Botrytis HTST - Meridian experience with SBC Chard; glutathione will act as a substrate for laccase and prevent juice browning Use of a yeast rehydration nutrient has been shown to increase aromatics in Sauvignon Blanc (Ugliano, 2008) 1

2 Preserving Glutathione Content of Juice/Wine When there isn t enough GSH, aromatics get oxidized 1. Maintain SO 2 Levels 2. Lees aging if lees are clean 3. Avoid excessive racking 4. Older barrels contribute less oxygen 5. Yeast with low nitrogen requirement 6. Inactivated Dry Yeast Preparation at grape stage benefits production and preservation of aroma in Sauvignon Blanc (2015 Suklje S. African) 7. Sauvignon Blanc: GSH increased with skin contact and was maintained if protected with neutral gas during pressing (2015 Pons, Dubourdieu) Glutathione Rich/Friendly Products Glutathione (GSH) is an important and wide spread antioxidant produced endogenously by both animal, plant and microbial cells The importance of GSH also lies in the potential to reduce SO 2 additions in wine AEB Elevage Glu, Fermol Glutaferm 1 yeast Laffort Fresharom, VL2 yeast, X5, X16 Lallemand Optimum White, Cross Evolution yeast Enartis Pro FT Free Thiol also has a chelating agent for heavy metals 2

3 Strength of Glutathione (2010 Practical Winery Laffort Research) When juice YAN is sufficient, GHS concentrations in juice and resulting wine are about the same. When juice YAN is <100 ppm very little GHS remains in the wine. (Yeast use it as a nitrogen source.) Laffort ARC Projects 2015 Impact of adding glutathione (15 mg/l) at bottling on the aldehydethiol aromas of Sauvignon Blanc after 4 years of ageing Control with GSH (15 mg/l added) Oxidative evolution (waxy and honey) Sotolon (µg/l) 19 6 Phenylacetaldehyde (ng/l) Fruity Aromas 4MMPOH (ng/l) MH (ng/l)

4 Laffort ARC Projects Impact of FRESHArom on Redox Status in White Wines Preliminary Data Glutathione Impact on Wine Ageing Post-Fermentation Glutathione (mg/l) EU OIV Activity on Glutathione OIV has approved </= 20 ppm GSH at bottling; is considering approval of yeasts rich in glutathione European Union Annex : OENO-TECHNO Treatment of musts with inactivated yeasts with guarantee level in glutathione OENO-TECHNO Treatment of wines with inactivated yeasts with guarantee level in glutathione 4

5 2017 S African Journal of Vit & Enol Gabrielli (IT), Tudo & du Toit (RSA), Kilmartin (NZ), Sieczkowski (Lallemand FR) CONCLUSION The addition of GSH or Dried Yeast Preparation (DYP) to Sauvignon blanc grape must has been shown to increase the concentrations of certain volatile compounds, which included thiols and some monoterpenes in the case of the DYP-added treatments. Nitrogenbased compounds and other components present in the DYP preparations are more likely responsible for the changes observed than the GSH added to the must due to DYP addition. However, this needs to be investigated further using other cultivars and DYP preparations. Glutathione [range in grapes 17 to 114 ppm] Timing: GHS can serve as a nitrogen source so best to add after 1 st nutrient addition Research indicates a level of 10 to 20 mg/l is the advisable range indicated so far. Caveat (Ugliano et al) - higher concentrations of H 2 S in wines treated with GHS prior to bottling Conclusion: further research needed to clarify the way in which GSH can contribute to wine quality improvement during all winemaking stages 5

6 Treating Oxidation Treating oxidized wines: Clean lees fining Fining agents PVPP/Casein TCA/TBA Check all cork finished bottles for TCA prior to use for topping Keep chlorine out of the winery Absorbed by plastic 6

7 Sulfides and Oxidized Mercaptans Thiols Aeration, nutrition, copper Aeration mercaptans may be oxidized to mono and di sulfides; may remove objectionable sensory but can be temporary Nutrition not always effective; some evidence counter-indicative Copper use judiciously, yeast absorb a large amount; they can disgorge it as they become dormant. Good cellar practice is to rack off lees if there have been sulfide issues so this copper release shouldn t be a problem Dimethyl Sulfide Australian Research (Ugliano 2008) found that this compound increased with aging depending on initial addition of DAP to the must Can increase fruity character; threshold is 25 to 60 ppb; found in wine up to 480 ppb Probably a breakdown product of amino acids Not related to H 2 S production Is related to grape variety, vintage, vine location (Sequrel 2004) and water stress (Grenache) (Dupré 2014) 7

8 Dimethyl Sulfide Removal with RO Eucalyptol 50 meters (160 ft) seems to be the safe distance from Gum Trees Stems and leaves have a greater concentration of Eucalyptol than grapes Amount continues to increase in a fermentation until pressing so press early This compound can completely overcome varietal character especially in Pinot Noir and other delicate fruit such as Grenache. Can be removed with RO 8

9 Thank you 9