Winemaking in the Classroom 3

1. Winemaking in the Classroom 3 Clarification, Finishing and Bottling Sirromet Wines Pty Ltd 850-938 Mount Cotton Rd Mount Cotton Queensland, Australia 4165 www.sirromet.com Courtesy of Jessica Ferguson Assistant Winemaker & Site Chemist Downloaded from seniorchem.com/eei.html

2. What next?

3. Clean-up, add preservative • When wine is dry, or by desired sweet style • cool vessel down – colder the better, to help stop yeast and encourage settling of dead yeast • add SO2 when cool – Camden tablets or Potassium Metabisulphite (PMS) salt • aim for >35mg/L Free SO2 • Consider that PMS is only 57% SO2 • At least 50% of added SO2 will convert to bound SO2 directly following fermentation

4. Clarification - Racking Initially, allow wine to settle Ensure that containers are full Transfer carefully (no splashing) to smaller containers, or top up containers and seal. Avoid oxygen/air exposure May need successive rackings to achieve clarification – more settling occurs following each racking

5. Racking • Separation of clear wine from settled solids (lees) • Best to use a siphon with the end of the hose held above the lees • Rack wine into a smaller container so that vessel is full • Always keep wine vessels full unless fermenting • This prevents spoilage due to oxidation or aerobic microbes

6. Further clarification aids Bentonite – clay mineral used for clarification Try 0.25gm/L dose in wine Make up as 5% slurry in water Make up day before use to allow swelling of particles mix vigorously (use electric beater) while adding powder slowly to hot water Add to wine immediately after SO2 addition, or after racking for further clarification Rack clear wine 2 days after bentonite addition Wine should not be chilled – bentonite works better over 10˚C

7. Safe wine storage • Full containers • low dissolved oxygen • Free SO2 >35mg/l @ pH 3.20 • no fermentable sugars left • Keep wine cool – 15˚C is great, but at least <20˚C.

8. Finishing wine – fining and stability • Consider acid addition trial for flavour and balance (can use citric or tartaric acid) • Other fining agents: powdered milk, gelatine, isinglass - to alter or reduce bitterness, phenolics, tannins • Good idea to trial all finings on bench first • 100mL wine samples, add solution of fining agent equivalent to final dose in wine • For example, to trial a 0.2g/L tartaric acid addition: add 0.2mL of a 10% tartaric acid solution to 100mL of wine on the bench

9. Finishing Wine - Stabilising Protein stability: More an issue for white-style wines, prevents protein haze in bottled wine Proteins are removed by bentonite fining Test for protein stability: heat a filtered wine sample for 6 hours at 80˚C, cool and check for haze formation Cold stability: Prevents tartrate precipitation in bottle, difficult to achieve on small volume wines and without a way of cold filtering without air exposure Could try refrigerating wine and racking wine off of any crystals that precipitate

10. Finishing Wine - Filtration May not be necessary for some red wines that have achieved good clarity through racking/fining alone Filtration options – depends on sweetness levels, persistent turbidity or clarity issues Gravity or small electric pad filters are available Suggest pad filter just prior to bottling – gives brilliance to wine Wine should not be chilled when filtering as this exacerbates dissolved oxygen pick-up

11. Bottling Logistics • In industry we would check the following pre-bottling: pH, titratable acidity, free/total SO2, CO2, H2S, alcohol, flavour, colour, dissolved oxygen, protein stability, tartrate (cold) stability, residual sugar, turbidity/clarity, specific gravity • Adjust Free SO2 levels to 35-40mg/L • Use clean, preferably sterilised bottles • Fill bottles carefully with no splashing (avoid increasing dissolved oxygen) • Seal with screw-caps, crown seals or corks

12. Finally….. A word of caution • If wine is not dry at bottling, be aware of the risk of re-fermentation • Increase SO2 levels pre-bottling to FSO2 > 40mg/L • Can also use Potassium Sorbate at 100-150mg/L as an extra preservative (ensure SO2 levels are adequate for sorbate to be effective) • Advise that wine should be drunk earlier rather than later!